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  • General Chemistry  (25,425)
  • Mice  (3,479)
  • EARTH RESOURCES AND REMOTE SENSING  (3,375)
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  • 1
    Electronic Resource
    Electronic Resource
    L3T4(CD4)-, Lyt-2(CD8)- and Mac-1(CD11b)-phenotypic leukocytes in murine cryptococcal meningoencephalitis (1995)
    Springer
    Mycopathologia 131 (1995), S. 159-166 
    Details
    ISSN: 1573-0832
    Keywords: Cryptococcus ; Immunity ; Immunohistology ; Meningoencephalitis ; Mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract An immunohistological study of L3T4(CD4)+ and LYT-2(CD8)+ lymphocytes, Mac-1(CD11b)+ monocytes and granulocytes in experimental murine cryptococcal meningoencephalitis was conducted. To assess the concomitant inflammatory reaction in an extracerebral site, livers were examined in parallel. Mice were infected i.v. withCryptococcus neoformans, group A/D, and organs were examined immunohistologically for CD4-, CD8- and monocyteand granulocyte-specific CD11b-phenotypic leukocytes over a period of 60 days. Intracerebrally, agglomerations of cryptococci formed pseudocysts that were surrounded by CD4+ and CD8+ lymphocytes at the end of the second week post-infection, followed by the invasion of monocytes and granulocytes into the lesions. After the fourth week post-infection, most of the invaded lesions were transformed into glious scars. Meningitis was usually marked and showed a homogenous distribution of CD4-, CD8- and CD11b-phenotypic cells, with a predominance of monocytes and CD4+ lymphocytes. Inflammatory infiltrates in the liver were found already 4 days post-infection. CD4+ lymphocytes and monocytes were distributed homogenously in the infiltrates, with a lower number of CD8+ lymphocytes being located rather in the periphery of the infiltrates. Comparing leukocyte kinetics in brain and liver, an important observation was the delayed immigration of immune cells at the intracerebral cryptococcal lesions as compared with the liver, and the different migration patterns of T-lymphocyte subgroups and macrophages. These results suggest that there are differential leukocyte migration patterns in the liver and brain following disseminated cryptococcosis. The immunological aspects of the observed leukocyte kinetics are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01102895
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  • 2
    Electronic Resource
    Electronic Resource
    Evaluating birth frequencies and embryonic lethality in transgenesis following pronuclear injection of HIV DNA (1995)
    Springer
    Journal of biomedical science 2 (1995), S. 146-153 
    Details
    ISSN: 1423-0127
    Keywords: Transgene ; Mice ; Embryogenesis ; HIV ; Toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The likelihood that expression of a foreign gene in a mammalian cell is deleterious to viability is confronted whenever novel transgenic animals are made. A pathological response to transgene expression is even desired in transgenic mouse models of human disease. The derivation of HIV-transgenic mice in our laboratory using multiple recombinant forms of an HIV provirus has resulted in mixed success best explained by the variable toxicity of the different transgenes. Employing a standardized approach to pronuclear injections, experimental variation amongst recombinant HIV transgenes was documented in terms of the percentage of pregnancies following embryo transfer into pseudopregnant mice and the percentage of transplanted embryos leading to term births in these pregnant females (giving rise to an index of birth success, SI). Results compiled over 5 years suggested that the SI reflected transgene toxicity, in this case of HIV gene products early in embryogenesis. These observations have guided the design of productive transgenes for mouse models of HIV-related diseases and may be generally applicable in transgenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02253065
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of pre- and post-irradiation glucan treatment on pluripotent stem cells, granulocyte, macrophage and erythroid progenitor cells, and hemopoietic stromal cells (1984)
    Springer
    Cellular and molecular life sciences 40 (1984), S. 1240-1244 
    Details
    ISSN: 1420-9071
    Keywords: Mice ; glucan treatment ; Co60-irradiation ; stem cells, pluripotent ; granulocytes ; macrophages ; erythroid progenitor cells ; hemopoietic stomal cells ; hemopoiesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Glucan, a beta-1, 3 polyglucose, was administered to mice either 1 h before or 1 h after a 650 rad exposure to cobalt-60 radiation. Compared to radiation controls, glucan-treated mice consistantly exhibited a more rapid recovery of pluripotent stem cells and committed granulocyte, macrophage, and erythroid progenitor cells. This may partially explain the mechanism by which glucan also enhances survival in otherwise lethally irradiated mice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01946654
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  • 4
    Electronic Resource
    Electronic Resource
    Metabolites of vitamin D in normal and X-linked hypophosphatemic mice (1984)
    Springer
    Calcified tissue international 36 (1984), S. 662-667 
    Details
    ISSN: 1432-0827
    Keywords: Vitamin D ; Hyp ; X-linked hypophosphatemia ; Metabolic bone disease ; Mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Hyp mice are a model for human X-linked hypophosphatemia (vitamin D-resistant rickets.) To determine whether an abnormality of vitamin D metabolism exists in this disease, the profiles of the metabolites of vitamin D were determined in normal andHyp mouse plasma.Hyp and normal mice were fed a vitamin D-deficient diet and received 1,23H-vitamin D3 at 16 Ci/mmol by stomach tube at 5 ng/g body weight (0.21 µCi/g b.w.) on alternate days for 14 days. The dose of vitamin D given maintained near normal plasma 25-OH-vitamin D. Thus the mice were in a vitamin D-replete state with all metabolite pools labeled with3H. Plasma was collected from 4 normal and 4Hyp mice. The plasma was extracted, and the extracts were chromatographed separately for each mouse on an LH-20 column. Each major peak of radioactivity was rechromatographed using high performance liquid chromatography on a Zorbax-Sil column using solvent systems known to resolve several vitamin D metabolites. Twenty-one radioactive peaks were identified. The disintegrations per minute of3H in each peak were quantified and converted to plasma concentration using the known specific activity of the administered vitamin D. The 25-OH-vitamin D accounted for 55% of the circulating radioactivity, and 24,25-(OH)2-vitamin D accounted for 22%. The plasma levels of 24,25-(OH)2-vitamin D were similar to levels previously reported by us using protein binding assays. No peaks of radioactivity were missing in the plasma extracts of theHyp mice. Also there was no evidence that plasma 24,25-(OH)2-vitamin D was elevated in theHyp mice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405387
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  • 5
    Electronic Resource
    Electronic Resource
    A biometrical genetic analysis of ethanol response in selectively bred Long-Sleep and Short-Sleep mice (1984)
    Springer
    Behavior genetics 14 (1984), S. 1-19 
    Details
    ISSN: 1573-3297
    Keywords: Mice ; alcohol ; selective breeding ; pharmacogenetics ; biometrical genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract A classical Mendelian cross was derived from Long-Sleep (LS) and Short-Sleep (SS) mice, lines selectively bred for differences in response to hypnotic doses of ethanol (ETOH). Biometrical genetic procedures applied to the selection phenotype, namely, duration of the ETOH-induced loss of the righting reflex, suggest that a simple additive genetic system controls this depressant response. Sex differences were present in the Mendelian cross generations that had the longest duration responses. An estimate of the number of loci differentiated by the selection was nine. Blood ethanol levels at the time of regaining the righting reflex in the seven genotypes of the Mendelian cross showed that the selection operated solely by changing tissue sensitivity to ethanol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066065
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of hydrocortisone on the phenotypic expression and inheritance of the Fused gene in mice (1983)
    Springer
    Theoretical and applied genetics 64 (1983), S. 275-281 
    Details
    ISSN: 1432-2242
    Keywords: Fused gene ; Mice ; Hydrocortisone ; Gene inactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study was undertaken to examine the effects of hydrocortisone injected into male mice on the phenotypic expression and inheritance of the Fused (Fu) gene in their offspring. Data were obtained indicating that there is a hydrocortisone-susceptible period during spermatogenesis. Hydrocortisone injections of males during this period resulted in a statistically significant decrease in the proportion of phenotypically Fu offspring. Genetic analysis with the use of the closely linked recessive marker tufted (tf) demonstrated that the deficit of phenotypically Fu individuals among offspring is not caused by the differential death of gametes, zygotes or embryos. According to genetic data, this deficit is due to a decrease in the penetrance of the Fu gene and partly to its inherited inactivation. The possible mechanisms of the observed phenomenon are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00274161
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  • 7
    Electronic Resource
    Electronic Resource
    Direct and correlated responses to selection for weaning weight, post-weaning weight gain and six-week weight in mice (1984)
    Springer
    Theoretical and applied genetics 67 (1984), S. 113-122 
    Details
    ISSN: 1432-2242
    Keywords: Mice ; Selection ; Growth ; Genetic correlation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Four lines of mice were formed from a common base population and selected for 37 generations for either increased 3-week weight (weaning weight), 6-week weight, 3–6 week gain, or maintained as a randomly bred control line. Realised heritability estimates for short-term (long-term) responses were 0.33±0.20 (0.07±0.10), 0.46±0.14 (0.26±0.09), 0.36±0.14 (0.24±0.11) for 3-week weight, 6-week weight and 3–6 week gain, respectively. Realised genetic correlations estimated from short-term (long-term) responses were 0.23±0.08 (0.35±0.10) between 3-week weight and 3–6 week gain; 0.82±0.04 (0.58±0.08) between 3-week weight and 6-week weight; and 0.81±0.04 (0.97±0.04) between 3–6 week gain and 6-week weight. The genetic correlation between 3-week weight and 6-week weight was asymmetric with a greater correlated response for 3-week weight when selecting for 6-week weight (1.06) than vice versa (0.63).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317015
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  • 8
    Electronic Resource
    Electronic Resource
    Male and female contributions to heterosis in lifetime performance of mice (1984)
    Springer
    Theoretical and applied genetics 67 (1984), S. 479-484 
    Details
    ISSN: 1432-2242
    Keywords: Heterosis ; Lifetime performance ; Mice ; Male and female ; Mate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Six straightbred lines of mice, some of their F1 crosses and a synthetic line were used to evaluate male and female contributions to heterosis in lifetime performance measured on females. Females from each straightbred line or F1 crosses were pair-mated randomly at day 42 with either a male of the corresponding genetic group or from a synthetic line, and pairs were maintained for 155 days (lifetime). Each mother was allowed to rear all young born alive until day 18 when the young were discarded. Data were analyzed using a model in which the group mean of lifetime performance was expressed as the sum of (additive direct) genetic and environmental effects for each of the male and female genetic groups used for mating. Comparison of group means for lifetime performance revealed that estimates of F1 heterosis due to male and female averaged 10 and 9% for number of parturitions during lifetime, 7 and 28% for total number of young born alive, 6 and 31% for total body weight of young born alive, 8 and 33% for total number of young raised to day 18, 9 and 43% for total body weight of young raised to weaning, and 8 and 8% for days from first mating to last parturition. The male's contribution to heterosis in lifetime performance was smaller than female's contribution for productive traits (total number of young born alive and at day 18, and total body weight of young born alive and at day 18), and was nearly equal in reproductive traits (number of parturitions during lifetime and days from first mating to last parturition).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264889
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  • 9
    Electronic Resource
    Electronic Resource
    Long-term restricted index selection in mice designed to change fat content without changing body size (1995)
    Springer
    Theoretical and applied genetics 91 (1995), S. 340-345 
    Details
    ISSN: 1432-2242
    Keywords: Selection index ; Restricted index ; Fat ; Mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The objective of this study was to determine if low secondary selection differentials, caused by selecting within full-sib families, may have accounted for the failure of an intended restricted selection index to reduce epididymal fat pad weight (EF) without changing body weight (BW) in mice. Replicate lines that had been selected within full-sib families for high (HE) or low (LE) EF, while holding BW constant, were crossed. After two generations of random mating, two replicates were sampled and selection initiated for the same restricted index criteria except that mass selection was used to increase the selection differentials. In both phases of selection the HE restricted index selection, designed to increase EF without altering BW, was in agreement with expectation. In contrast, the LE index, designed to decrease EF without changing BW, did not agree with theory since BW increased while EF decreased only slightly. Therefore, reduced selection differentials could not explain the deviation from theory. A possible explanation may reside in the restricted selection index being more sensitive to changes in genetic parameters due to shifts in gene frequency as a consequence of the selection applied. However, linkage disequilibrium and genetic drift can not be ruled out as contributing factors to the asymmetry of response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220897
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  • 10
    Electronic Resource
    Electronic Resource
    Genetic interpretation and analysis of diallel crosses with animals (1983)
    Springer
    Theoretical and applied genetics 65 (1983), S. 17-23 
    Details
    ISSN: 1432-2242
    Keywords: Diallel cross ; Maternal effects ; Heterosis ; Mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A genetic framework was developed for the interpretation of statistical parameters estimated from a diallel experiment among a fixed set of lines. These included average direct genetic, average maternal genetic, general combining ability, reciprocal, and line and specific direct and maternal heterotic effects. The genetic model is based on direct and maternal additive and dominance genetic effects as would be expected in animal species. The model assumes that dominance is the underlying basis of heterosis. As an example, litter size at birth was analyzed from a 5 × 5 diallel cross with mice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276256
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  • 11
    Electronic Resource
    Electronic Resource
    Influence of early pregnancy on reproductive rate in lines of mice selected for litter size (1980)
    Springer
    Theoretical and applied genetics 57 (1980), S. 209-220 
    Details
    ISSN: 1432-2242
    Keywords: Mice ; Early puberty ; Litter size ; Selection ; Reproductive rate ; Pheromone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The influence of male-induced early puberty on female reproductive rate was determined in three lines of mice differing in litter size and body weight. The lines originated from a single base population and had undergone 20 generations of selection for the following criteria: large litter size at birth (L+), large litter size and small 6-week body weight (L+W−), or small litter size and large 6-week body weight (L−W+). Females were paired with a mature intact male of the same line at 3, 5 or 7 weeks of age. Mean mating age, averaged over lines, was 26.5 ± .3, 38.3 ± .3 and 52.7 ± .3 days. Exposure to a mature male accelerated female sexual maturation in each line. When contrasted with their sibs mated at a later age, early-pregnant females from each line exhibited a decline in one or more component of reproductive performance, suggesting that the physiological state of the very young female was not optimum for normal pregnancy. In comparisons of early and later mating ages, all three lines showed a decreased littering rate at first mating, number born alive, and individual birth weight of progeny adjusted for litter size; L+ and L+W− mice showed an increased perinatal mortality rate; L+ and L−W+ had a reduction in litter size at birth. When the L+, L+W− and L−W+ lines were compared with an unselected strain and a line selected for high postweaning gain in similar experiments, a genotype by environment interaction was apparent since all lines did not respond in a similar manner to early mating. The line ranking for litter size at birth for each age at male-exposure was L+〉L+W−〉L−W+, despite the significant line by age interaction. When litter size was adjusted by covariance for body weight at mating, the significant effects of age at male-exposure and line by age interaction were eliminated. All fertile females were remated after they had weaned their first litter to obtain information on litter size in parity two. Line differences in litter size at birth and number born alive were uniform across parities. An age by parity interaction was evident since the decreased fecundity at younger ages of male exposure in the L+ and L−W+ litters of parity one was not evident in parity two. Litter feed efficiency during first parity gestation was defined as litter birth weight divided by either cumulative feed intake of the dam from mating to parturition (GEI) or cumulative feed intake from weaning to parturition (GEII). The ranking of lines for GEI and GEH was L+〉 L+W−〉L−W+, but when feed efficiency was adjusted for littering rate, L+W− and L−W+ were not significantly different. With regard to age at mating, the ranking for GEI (7 wk 〉 5 wk 〉 3 wk) was reversed from GEII (3 wk 〉5 wk 〉 7 wk) and these significant differences were maintained after adjustment for littering rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264673
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  • 12
    Electronic Resource
    Electronic Resource
    Selection for efficiency of feed utilization in growing mice (1981)
    Springer
    Theoretical and applied genetics 59 (1981), S. 129-137 
    Details
    ISSN: 1432-2242
    Keywords: Selection ; Mice ; Feeding Efficiency ; Correlation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Selection was practised for improved feed efficiency (gain/feed intake) of mice on two alternative feeding regimes. In one set of lines animals were fed ad libitum, in the other set they were individually fed a fixed amount of feed (about 10% below the control ad libitum intake) which was not changed over generations. For each treatment, a pair of replicate lines (E) were selected on efficiency from 3–5 weeks of age for 8 generations and another pair (L) from 5–7 weeks for 7 generations. A control line was maintained for both E and L lines. In terminal generations mice from each line were tested on each feeding regime, and carcasses of ad libitum fed mice were analysed. The realized heritability (within families) for efficiency averaged 13%, without much variation over treatments. In the E lines efficiency increased by about 18% of the control mean and in the L lines by about 60%, although absolute changes were small, and responses were similar on the two feeding regimes. Weights at the start of test decreased in the E lines and increased in the L lines; weights at the end of test increased in both. When tested on the alternative regimes, no interactions were detected for live weights, weight gains or efficiency; selection under fixed intake led to the same increase in appetite as did that under ad libitum. There were no interactions for carcass composition. Selection for efficiency led to an increase in fatness on both selection regimes and both weight ranges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264964
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  • 13
    Electronic Resource
    Electronic Resource
    Correlated responses of growth traits to selection for high and low plasma alkaline phosphatase in mice (1982)
    Springer
    Theoretical and applied genetics 62 (1982), S. 281-287 
    Details
    ISSN: 1432-2242
    Keywords: Growth ; Alkaline phosphatase ; Selection ; Correlated responses ; Mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effectiveness of two way selection for plasma alkaline phosphatase (ALP) was investigated in order to determine its influences on growth traits through thirteen generations. The responses of the two lines selected for high (HP) and low (LP) ALP at 45 days of age were compared to that of the mice selected for large (L) and small (SM) body size. The selection responses of plasma ALP were very effective for both HP and LP lines, with average responses per generation calculated from linear regressions of 0.227±0.037 and −0.088±0.022 respectively. The final levels of ALP in HP and LP were 5.54±0.71 and 1.27±0.20 in the thirtheenth generation, while the SM, L and base population had levels of 3.49±0.08, 0.86±0.55 and 2.77±0.56 respectively. The body weight at 45 days of age in LP (31.4±1.4 g) as a correlated response was significantly higher than HP (23.4±1.8 g) at generation 10. The correlated response of milk yield, measured by weight gain up to 12 days of age, was significantly greater in the LP line than in HP, but the correlated response of gains after weaning was not so different as the response of milk yield. The response of litter size and weight in LP showed significant higher levels than that of HP, but pups' birth weight did not differ between LP and HP. It is suggested that the correlated response of milk yield contributed more to the divergence of body size between HP and LP than the gain after weaning. Realized heritabilities of ALP were 0.335±0.059 (HP) and 0.279±0.051 (LP). Realized genetic correlations between ALP and 45 days' body weight were −0.27±0.13 (HP with SM) and −0.52±0.19 (LP with L). Realized genetic correlations between ALP and milk yield were −0.95±0.03 (HP) and −0.37±0.29 (LP). Correlations between ALP and postweaning gains were fairly low.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276252
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  • 14
    Electronic Resource
    Electronic Resource
    Direct and correlated responses to selection for post-weaning weight gain on ad libitum or restricted feeding in mice (1982)
    Springer
    Theoretical and applied genetics 63 (1982), S. 145-150 
    Details
    ISSN: 1432-2242
    Keywords: Mice ; Selection ; Growth rate ; ad libitum feeding ; Restricted feeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Selection for post-weaning weight gain in mice from 21 to 42 days, on either a full or restricted feeding level during this period was carried out for seven generations. Control lines were maintained for each feeding level. The rate of selection response was higher on full feeding due to a higher heritability and a larger phenotypic variance. Realised heritabilities of 0.29±0.05 and 0.19±0.04 for selection on full and restricted feeding respectively, were in close agreement with base population estimates. Selection on full feeding led to positive correlated responses in 21 day weight, 42 day weight, food intake and efficiency between 21 and 42 days, and 42 day tail length, but with little change in reproductive performance. Correlated responses to selection on restricted feeding were reduced 21 day weight, but an increase in 42 day weight and increased efficiency from 21 to 42 days. However, overall reproductive performance fell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00303697
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  • 15
    Electronic Resource
    Electronic Resource
    Retarded myogenic cell replication in regenerating skeletal muscles of old mice: an autoradiographic study in young and old BALBc and SJL/J mice (1995)
    Springer
    Cell & tissue research 280 (1995), S. 277-282 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Skeletal muscle ; Regeneration ; Ageing ; Strain-specific muscle precursor replication ; Autoradiography ; Mice ; BALBc (SJL/J)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The patterns of skeletal muscle precursor cell replication after crush injury were compared by the use of autoradiographic techniques, in young (4-week-old) and old (39-week-old) BALBc and SJL/J mice. Similar comparisons were made between cut and crush lesions in old BALBc muscle. Muscle precursor cell replication commenced at 18–24 h after injury in both young and old muscles from both strains of mice. In young BALBc muscle the peak of myogenic activity at 60 h was 36 h earlier than in old mice. SJL/J muscle responded more rapidly than did BALBc: in young SJL/J the peak myogenic activity was at 46 h (14 h earlier than in young BALBc muscle), and in old SJL/J muscle the peak activity at 72 h was 24 h earlier than in old BALBc muscle. In all mice (both young and old) myogenic cell replication was substantially reduced by 120 h after injury. A comparison of the timing of muscle precursor cell replication in cut and crush lesions in old BALBc mice revealed a more rapid response in the cut lesion; this difference between the lesions is comparable with data from identical lesions in 6–8-week-old BALBc mice (McGeachie and Grounds 1987). However, the peak of myogenic replication in the older mice in the present study was some 26–36 h later than in the younger 6–8-week-old mice. These experiments show that, whilst muscle precursor cell replication commences at approximately the same time (about 24 h) after injury in young and old mice, the peak level of activity is delayed by some 24–36 h in old mice. In addition, the SJL/J mouse strain responds more rapidly and prolifically to muscle injury than does the BALBc strain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307799
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  • 16
    Electronic Resource
    Electronic Resource
    Flow cytometric analysis of mouse hepatocyte ploidy (1984)
    Springer
    Cell & tissue research 238 (1984), S. 643-647 
    Details
    ISSN: 1432-0878
    Keywords: Binucleate cells ; Flow cytometry ; Hepatocytes ; Polyploidy pattern ; Mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Preparative and mathematical procedures are presented for the investigation of the ploidy pattern of liver cells. The DNA content of enzymatically-isolated liver cells and of nuclei was measured by flow cytometry. The true DNA content could not be measured directly due to superposition of statistical coincidences (demanding “first mode correction”) and incomplete separation of the nuclei in binucleate hepatocytes (demanding “second mode correction”). The statistical coincidences (caused by simultaneous measurement of two or more particles or subsequent reaggregation of particles) were corrected by splitting the “unnatural” i.e., aneuploid DNA content, and classifying it with the normal ploidy classes. In addition, the higher normal ploidy classes were reduced by the proportion of the measured coincidences in favour of the lower ones. The second mode correction applied to nuclear distributions only. It is a probability calculation based on counting nuclear pairs on microscope slides, and resulted in a 10% increase of diploid nuclei and a larger standard deviation between the age groups. 8c and 16c values were reduced. The tetraploid values were unchanged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219883
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  • 17
    Electronic Resource
    Electronic Resource
    Issues in the genetics of social behavior: Revisited (1996)
    Springer
    Behavior genetics 26 (1996), S. 463-470 
    Details
    ISSN: 1573-3297
    Keywords: Mice ; agonistic behavior ; aggression ; homogeneous set ; standard tester ; social behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Though social behavior has not been overlooked by behavior geneticists, the number of studies is small when compared to those on individual traits. One reason for the neglect may be the difficulty of making connections between genes and social behaviors, which by definition involve the interaction of two or more organisms. Fuller and Hahn (1976) addressed this issue and described three means of establishing social groups that would facilitate genetic analysis. We survey the literature on agonistic behavior in mice from 1976 through 1994 and describe interesting uses of those three methods. One of those methods (the standard tester design) often employs a “noninteractive” social partner. We present data showing that the standard tester design may be more valuable when using an evocative and interactive standard tester.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02359750
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  • 18
    Electronic Resource
    Electronic Resource
    Unimpaired delayed type hypersensitivity reactions in mice infected withTrypanosoma cruzi strain Y (1980)
    Springer
    Parasitology research 61 (1980), S. 179-185 
    Details
    ISSN: 1432-1955
    Keywords: Trypanosoma cruzi ; Delayed hypersensitivity ; Mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Delayed type hypersensitivity reactions (DTH) to DNFB in C3H (susceptible) and (CBA×C57B1/10)F1 (resistant) mice were not impaired inTrypanosoma cruzi strain Y infections. Mice were infected IP with 100 parasites and sensitized or challenged 11 days after infection at the peak of parasitaemia. DTH reactions were found to be enhanced in C3H infected mice.
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    The growth ofHymenolepis microstoma in intact and gonadectomized mice (1980)
    Springer
    Parasitology research 61 (1980), S. 243-247 
    Details
    ISSN: 1432-1955
    Keywords: Hymenolepis microstoma ; Mice ; Orchiectomy ; Ovariectomy ; Growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Gonadectomy or sex of the host had no effect on the mean dry weight ofHymenolepis microstoma examined on day 12 postinfection (p.i.). However, on day 20 p.i. worms from intact or sham-operated male mice were significantly heavier than those recovered from the corresponding groups of female hosts. Orchiectomy of hosts lowered the average weight of these older worms, but ovariectomy had no effect.
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    Humoral suppression inTrypanosoma cruzi infection in relation to the timing of antigen presentation (1980)
    Springer
    Parasitology research 64 (1980), S. 85-93 
    Details
    ISSN: 1432-1955
    Keywords: Trypanosoma cruzi ; Immunosuppression ; Immunenhancement ; Mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract (CBA×C57 B1/10)F1 mice infected intraperitoneally with 100 parasites ofTrypanosoma cruzi strain Y developed an infection with acute and chronic phases. Humoral suppression to sheep red blood cells was evident in both phases but enhancement of the response was achieved only at the beginning of the infection. A mitogen secreted by the parasite could explain both phenomenons.
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    URL: http://dx.doi.org/10.1007/BF00927059
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    Predatory aggression in male mice selectively bred for isolation-induced intermale aggression (1995)
    Springer
    Behavior genetics 25 (1995), S. 361-366 
    Details
    ISSN: 1573-3297
    Keywords: Mice ; aggression ; isolation-induced aggression ; predatory aggression ; selected lines ; genetic variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Male mice differing in their genetically determined disposition for isolation-induced intermale aggression were compared on behaviors related to predatory aggression. An ongoing sequence of selective breeding established high-aggressive (Turku Aggressive: TA) and low-aggressive (Turku Non-Aggressive: TNA) lines from an outbred Swiss albino foundation stock. The parental strain, designated the Normal (N) strain, has been kept as a control line and is bred without regard to aggressiveness. Testing consisted of dropping a live cricket into the home cage of the individually housed experimental mice. Results showed that the TA males displayed shorter latencies to attack and spent more time in chasing, attacking, and consuming crickets than did TNA and N males. The TNA males displayed significantly less predatory aggression than both the TA and N males. When brothers of the males tested for predatory aggression were tested for intermale aggression, a similarly significant effect of breeding line was obtained for the latency to attack. Testing consisted of placing an intact male mouse into the cage of the male to be tested. The results suggest that there may be parallels in genetic variation between intermale and predatory attacking.
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    Genetic and Developmental Influences on Infant Mouse Ultrasonic Calling. II. Developmental Patterns in the Calls of Mice 2–12 Days of Age (1998)
    Springer
    Behavior genetics 28 (1998), S. 315-325 
    Details
    ISSN: 1573-3297
    Keywords: Mice ; ultrasonic calls ; infants ; individual differences ; signatures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Infant house mice, Mus musculus, produce ultrasonic calls that reliably lead to retrieval by adult mice. While individual differences in calls have been demonstrated both among and within species, the influences of age and sex on call characteristics have not been systematically investigated in mice. This study examined the influences of age, sex, and genotype (inbred versus hybrid) on the rate, length, and frequency characteristics of the calls of 486 male and female mice from 2 to 12 days of age. Rate of calling followed a shallow inverted U-shaped function across days. Call lengths decreased and call frequency characteristics increased, in a linear manner, with age. Females emitted fewer calls, with a smaller bandwidth, at some ages than males. Hybrid pups produced more calls of greater length and a lower frequency than inbred pups. These results indicate the presence of cues that could allow adult mice to behave differentially toward pups as a function of their age and sex.
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    URL: http://dx.doi.org/10.1023/A:1021679615792
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    Genetic and Developmental Influences on Infant Mouse Ultrasonic Calling. I. A Diallel Analysis of the Calls of 3-Day Olds (1997)
    Springer
    Behavior genetics 27 (1997), S. 133-143 
    Details
    ISSN: 1573-3297
    Keywords: Mice ; ultrasounds ; ultrasonic calls ; infants ; diallel cross ; individual differences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Ultrasonic calls produced by young mice reliably elicit investigation and retrieval by adults. While there are large individual differences in the characteristics of these calls, little work has been done to partition that variation. We completed a 4 × 4 diallel cross and Hayman analyses on several characteristics of these cries. The major result was the detection of directional dominance toward a higher rate of calling, longer calls, and calls of lower overall frequency with a greater bandwidth. Within the context of biometrical genetic theory, we conclude that calls with such characteristics may have important fitness value. Extending this idea, we propose that within the population sampled for this study (the animals of the four inbred strains and 12 F1 hybrid groups), the calls most effectively eliciting investigation and retrieval would be calls with the average hybrid values of the diallel cross.
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    Diastereomerically Pure 1,2-Diols by Nucleophilic Displacement Reactions of 3-Oxetanols - A Study Directed Towards the Identification of Suitable Nucleophiles and the Elucidation of Possible Side Reactions (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2161-2169 
    Details
    ISSN: 1434-193X
    Keywords: Photocycloaddition ; Ring opening ; Oxetanes ; 1,2-Diols ; Alkyldealkoxylation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ring opening of 3-isopropyl-2-phenyl-3-oxetanol (2a) by various nucleophiles has been studied. In the presence of BF3 as a Lewis acid, a clean reaction at the less substituted C-4 position was observed and the corresponding 1,2-diols 6-11 and 21-23 were isolated in diastereomerically pure form (47-97% yield). Alkyl-, aryl-, alkynyl- and alkenyllithium compounds proved to be suitable carbon nucleophiles. Deprotonated thiols were used as sulfur nucleophiles. An alkoxide derived from benzyl alcohol and an amide derived from benzylamine reacted less readily under these conditions, yielding the 1,2,3-trifunctional compounds 24 (42% yield) and 26 (54% yield). Other 2-phenyl-3-oxetanols such as 2b and 2c can also be employed as electrophiles, whereas 2-anisyl derivatives preferentially undergo rearrangement reactions, as exemplified by the conversion of oxetane 16 to the hydroxy ketone 17 (84% yield). The superior behaviour of 3-oxetanols as compared to their silyl derivatives in reactions with nucleophiles became evident from the reaction of 3-silyloxyoxetane 1a with alkyllithium reagents. A β elimination occurred upon treatment with nBuLi, which, after pericyclic ring opening and addition of nBuLi, yielded the allylic alcohol 20.
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    Fluorescence Quenching of Ester-Substituted DBO-Type Azoalkanes by Olefins and Arenes: Electronic and Steric Effects, Exciplex Formation and Hydrogen Abstraction (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2177-2179 
    Details
    ISSN: 1434-193X
    Keywords: Azoalkanes ; DBO ; Fluorescence quenching ; Exciplexes ; Hydrogen transfer ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fluorescence of the DBO derivatives 1-3 is efficiently quenched by olefins and arenes, exciplex formation and hydrogen transfer operate as quenching mechanisms. The electron-accepting ester groups in the azoalkanes 1-3 promote significantly more effective quenching compared to the parent DBO. Steric hindrance accounts for the differences in the quenching efficiencies, but electronic effects dominate
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    Fragmentation Reactions of Quaternized γ-Amino Alcohols - Diastereoselective Synthesis of Highly Functionalized Oxetanes and Unsaturated Aldehydes and Ketones with a (Z)-C—C Double Bond (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2185-2191 
    Details
    ISSN: 1434-193X
    Keywords: Mannich bases ; γ-Amino alcohols ; Grob fragmentation ; (Z)-Alkenes ; Oxetanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quaternized γ-amino alcohols 5 derived from ternary iminium salts 2 are stereospecifically converted into both unsaturated aldehydes/ketones 6 with a (Z)-C—C double bond in a Grob-type fragmentation and highly functionalized oxetanes 7 by intramolecular substitution.
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    An Asymmetric Domino Three-Component Synthesis of β-Lactams (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2201-2207 
    Details
    ISSN: 1434-193X
    Keywords: Antibiotics ; Asymmetric synthesis ; β-Lactams ; Michael additions ; Multicomponent reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lithium dialkylcuprates react either in a sequential one-pot or in a domino “three-component” fashion with chiral Michael acceptors, like Oppolzer's N-enoyl-2,10-camphorsultams 7 and 11 or ‘Evans’ N-enoyl-4-phenyl-1,3-oxazolidin-2-ones 8 and 13, and N-(methoxycarbonylmethylidene)(4-methoxyphenyl)amine 9 to afford the corresponding cis-3-alkyl-4-methoxycarbonyl-1-(4-methoxyphenyl)azetidin-2-ones 10, 14-15 in overall yields of 40-67% and enantiomeric excesses of 91-99%.
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    Reactions of 3-Nitro-ν-benzylideneacetophenone with Carbanions Containing Leaving Groups (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2229-2235 
    Details
    ISSN: 1434-193X
    Keywords: 3-Nitro-ω-benzylideneacetophenone ; Carbanions ; Michael addition ; Intramolecular vicarious nucleophilic substitution of hydrogen ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-Nitro-ω-benzylideneacetophenone (1) reacts with carbanions containing leaving groups to give addition products to the electrophilic side chain. As a result of conjugated addition and subsequent intramolecular vicarious nucleophilic substitution of hydrogen (VNS) in the nitroaromatic ring of 1 in the position para to the nitro group, 4-cyano-7-nitro-3-phenyl-1,2,3,4-tetrahydronaphthalen-1-one and 4-cyano-7-nitro-3-phenylnaphth-1-ol are obtained. Smooth intramolecular VNS in the position para to the nitro group was observed for 4-chloro-1-(3-nitrophenyl)-3-phenyl-4-(p-tosyl)butanol.
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    Structure of the Dimers Obtained From the Reduction of 1-Benzyl-3,5-bis(dialkylcarbamoyl)pyridinium Ions - Models of NAD+ (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2237-2243 
    Details
    ISSN: 1434-193X
    Keywords: Conformation analysis ; Electrochemistry ; Nitrogen heterocycles ; Dimerization ; Mechanism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In aqueous media the one-electron reduction of the title compounds on a mercury pool generally gives rise to three dimers, which are distinguishable by HPL chromatography. From spectroscopic analyses it has been possible to propose a structure for these conformers and their stability has been studied. Two conformers are unstable, yielding the third conformer. A mechanism is proposed for this transformation.
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    Nucleotide Delivery from cycloSaligenyl-3′-azido-3′-deoxythymidine Monophosphates (cycloSal-AZTMP) (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 837-846 
    Details
    ISSN: 1434-193X
    Keywords: AZT ; cycloSal-pro-nucleotide ; Prodrugs ; Nucleotide delivery ; HIV chemotherapy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of our cycloSaligenyl- (cycloSal) pronucleotide concept to the approved anti-HIV dideoxynucleoside 3′-azido-3′-deoxythymidine AZT (1) is reported. This pro-nucleotide concept has been designed to deliver the corresponding 3′-azido-3′-deoxythymidine monophosphate AZTMP (2) by selective chemical hydrolysis from the lipophilic precursors cycloSal-AZTMP 4a-h. All derivatives 4a-h were synthesized using differently substituted salicyl alcohols 7a-h as starting materials. In hydrolysis studies, compounds 4 decomposed selectively releasing AZTMP (2) and the salicyl alcohols 7 following the designed tandem reaction. Furthermore, due to the electronic properties introduced by substituents, the half-lives of the triesters 4 could be ajusted over a wide range. Phosphotriesters 4 exhibited considerable biological activity in HIV-1 and HIV-2 infected wild-type human T-lymphocyte (CEM/O) cells, whereas, contrary to our expectations, nearly all activity was lost in HIV-2 infected thymidine-kinase-deficient CEM cells.
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    A Constrained Diketopiperazine as a New Scaffold for the Synthesis of Peptidomimetics (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 853-859 
    Details
    ISSN: 1434-193X
    Keywords: N-Alkylation ; Diketopiperazine building block ; Peptidomimetics ; RGD analogues ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As a new scaffold for peptidomimetic synthesis, a highly constrained bifunctional diketopiperazine, 4, has been prepared by smooth N-alkylation with tert-butyl bromoacetate. As a first application, we describe herein the synthesis of new peptidomimetics of the Arg-Gly-Asp (RGD) sequence. The product 30, which shows a selective platelet-aggregation inhibiting activity, can be used as a lead for the preparation of more potent products.
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    On the Reaction of Aminoxyls with Dioxiranes (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 871-876 
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    ISSN: 1434-193X
    Keywords: Dioxirane ; Homolysis, induced ; Aminoxyl ; Oxidation ; Spin-trapping ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the reactions of dimethyldioxirane (1a) and methyl(trifluoromethyl)dioxirane (1b) with 2,2,6,6-tetramethylpiperidinyl-1-oxyl (2) (TEMPO) in acetone, the corresponding methoxyamine 1-methoxy-2,2,6,6-tetramethylpiperidine (5) is produced in ≥98% yield, both in air and under N2, and in the absence or presence of a hydrocarbon (adamantane). Kinetic experiments show that aminoxyl 2 triggers the radical decomposition of the dioxirane, in addition to scavenging methyl radicals derived therefrom. The reactions of an aminoxyl less prone to oxidation, namely 1,2-dihydro-2-methyl-2-phenyl-3H-indol-3-one-1-oxyl (4), with dioxiranes 1a and 1b in acetone have also been studied. In these cases, not only is the corresponding methoxyamine 8a produced (yield 12-16%), but quinoneimine-N-oxides 10 (yield 12-21%) and 11 (yield 18-19%) are also formed. Furthermore, significant amounts (8-14%) of the amine 9 (the product of deoxygenation of 4) can be isolated. These observations provide useful information concerning the free-radical mechanism that follows the initial attack by the aminoxyl at the dioxirane.
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    A Blue Excitable Charge-Transfer Fluorescent Probe and Its Fluorogenic Derivative (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2373-2377 
    Details
    ISSN: 1434-193X
    Keywords: Charge-transfer fluorescence ; Fluorogenic probe ; Fluorescence labelling ; Maleimide group ; Solvatochromism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structural modification of the highly fluorescent donor-bridge-acceptor molecule “Fluoroprobe” (FP) is shown to extend the excitation window to longer wavelengths. The resulting “Fluorotrope” (FT) shows appreciable absorption in the 350-420-nm range, so that visible (blue) light can be used for excitation. Further functionalization with a maleimide group results in the novel fluorogenic reagent MaleimidoFluorotrope (MFT) which yields fluorescent adducts with amines, thiols and other reactive groups that add to the double bond of the maleimide. The fluorescence wavelength of these adducts is extremely sensitive to the polarity and mobility of the medium.
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    Polylithiated β-Peptides: like-Selective C-Terminal Alkylation of Boc-β-HVal-β-HAla-β-HLeu-OMe (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2379-2387 
    Details
    ISSN: 1434-193X
    Keywords: β-Peptides ; Polylithiation of peptides ; Li-enolates of peptides ; Back-bone alkylation of β-peptides ; Diastereoselective alkylation of β-peptide enolates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of N-Boc-protected β-tripeptide derivatives with or without N-methyl groups and with free or Me-ester-protected C terminus has been prepared (8-14, 16, 17). As with α-peptides (→ A), the β-peptide derivatives can be polylithiated (→ B, C). No epimerization of stereogenic centers and no β elimination (exception 17 → 24) is observed upon treatment with bases as strong as tBuLi. The C terminal ester Li-enolate moiety of tetralithio β-tripeptides (cf. C) can be selectively alkylated with methyl, benzyl and allyl halides, and with tert-butyl bromoacetate in yields ranging from 35-80% (8 → 18, 14 → 20-23).
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    Synthesis of Analogues of Brassinosteroids from Chenodeoxycholic Acid (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2405-2407 
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    ISSN: 1434-193X
    Keywords: Natural products ; Steroids ; Chenodeoxycholic acid ; Brassinosteroid analogues ; Biological activity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and spectroscopic characterization of two new bioactive analogues of brassinosteroids with a 24-hydroxylated cholanic side chain, an A/B ring cis-junction and oxygenated functions in C-7 is described.
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    Syntheses and Properties of S2-Bridged Benzidines (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2409-2416 
    Details
    ISSN: 1434-193X
    Keywords: Sulfur heterocycles ; Rearrangements ; Reductions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of 1,2-benzodithiino[5,4,3-cde][1,2]benzodithiin-2,7-diamine (1) and dithio-bridged benzidine 2 have been achieved. The starting material for the synthesis of 1 was 1,3-diiodo-5-nitrobenzene (15) which was transformed by conventional means into 1,2-bis[3,5-bis(ethylthio)phenyl]diazane (19). The benzidine rearrangement of 19 in the presence of HBF4 at -30 °C yielded 4,4′-diamino-2,2′,6,6′-tetraethylthiobiphenyl (20) in 50 % yield. Treatment of 20 with sodium in ammonia and work-up in the presence of air yielded 1. The latter compound could be reduced with LiAlH4 to the tetrathiol 20a. The starting material for the preparation of 2 was 3-chloro-1-iodo-5-nitrobenzene (23), a side product of the preparation of 15. It was transformed analogously to the preparation of 1 into 1,2-bis(3-ethylthiophenyl)diazane (28). The benzidine rearrangement of 28 in presence of HBF4 at -30 °C afforded 4,4′-diamino-2,2′-bis(ethylthio)biphenyl (29) in 49 % yield. Treatment of 29 with sodium in ammonia and work-up under aerobic conditions yielded 2. Quantitative reduction of 2 to the thiol 29a could be achieved with LiAlH4. The reversible electrochemical reduction of 1 on unmodified glassy carbon electrodes leads to a product to which the structure of 3 was assigned.
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    Stereoelectronic Inhibition of Deprotonation in the Radical Cation of N-Benzylpiperidine: a Contribution to the Debate on the Mechanism of N-Dealkylation of Tertiary Amines (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2425-2429 
    Details
    ISSN: 1434-193X
    Keywords: N-Heterocycles ; Porphyrins ; Radical cations ; N-Dealkylation ; Stereoelectronic effects ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Evidence for a stereoelectronic inhibition of deprotonation of the radical cation of N-benzylpiperidine is presented. This stereoelectronic effect, which is due to the cyclic structure of the precursor, provides a tool to differentiate hydrogen-atom- versus electron-transfer routes in the biomimetic oxidative N-dealkylation of tertiary amines: the electron-transfer route appears to be the operating mechanism.
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    (-)-(M,7S)-Colchicine and (-)-(M,7S)-10-Ethylthiocolchicide/Alkyne Cycloaddition Reactions: Synthesis of Novel Colchicine Derivatives by Consecutive [4+2] and [3+2] Cycloadditions (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2451-2460 
    Details
    ISSN: 1434-193X
    Keywords: Colchicine ; 10-Ethylthiocolchicide, diene properties of ; π-Facial diastereoselectivity ; Consecutive [4+2],[3+2] cycloadditions ; Atropisomerism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cycloaddition reactions of the facially dissymmetric diene moiety of (-)-(M,7S)-colchicine (5) and (-)-(M,7S)-10-ethylthiocolchicide (9) to various alkynes have been studied. With 5 and the dienophilic benzyne (3), dimethyl acetylenedicarboxylate (DMAD) (4) and cyclooctyne (6) as starting materials all cycloadditions could be realized with high regioselectivity at the 8,12-positions of the alkaloid. The approach of the dienophiles preferentially occurred toward the syn π-face of the diene. In contrast to the cycloaddition mode of 5 the ethylthiocolchicide 9 surprisingly reacted in a different manner. With benzyne as starting material a novel [3+2] cycloaddition of the thioenol ether moiety of 9 towards the dipolarophilic benzyne is supposed, affording the unexpected colchicide 10 after [1,5]H shift of the primarily formed cycloadduct followed by cleavage of the C-S linkage. With DMAD (4) and cyclooctyne (6) the reaction course is more complex. In a consecutive [4+2]/[3+2] cycloaddition (or vice versa) followed by a thermally induced cycloreversion of a not identified intermediate DMAD (4) gives rise to the polycyclic thiophene derivative 13 and the novel allocolchicinoid 14. In a similar way cyclooctyne (6) yielded three products, the thiophene-annulated homobarrelenones 18 and 19 and the tetracyclic allocolchicinoid 21. The structures of the novel colchicine derivatives were assigned on the basis of spectral data, those of the cycloadducts 1 and 19 were verified by X-ray crystallography. For the unprecedented formation of the various allocolchicinoids by consecutive [4+2]/[3+2] cycloadditions plausible reaction pathways are suggested, as far as possible. In addition the inhibitory effects on the tubulin polymerization reaction in vitro of 10, 14, and 21 are reported.
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    Exploration of High-Pressure Cycloadducts of Furans and Citraconic Anhydride as Precursors for CD-Ring Fragments of Paclitaxel and Its Analogues (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2483-2492 
    Details
    ISSN: 1434-193X
    Keywords: Paclitaxel (Taxol®) ; Paclitaxel CD-ring ; High-pressure Diels-Alder reactions ; Furan cycloadditions ; Ether cleavage in 7-oxabicyclo[2.2.1]heptanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The high-pressure promoted Diels-Alder reactions between several furans and citraconic anhydride have been studied and the cycloadducts obtained have been explored in new straightforward routes to the CD-ring fragment of paclitaxel. The reaction between furan and citraconic anhydride afforded the exo cycloadduct diastereoselectively, whereas a variety of 2-substituted furans afforded approximate 1:1 mixtures of exo regioisomers. Separation of both regioisomers was accomplished after either diastereoselective esterification or regioselective reduction of the anhydride function. Ether cleavage of the bicyclic compounds by either high-pressure promoted ether cleavage or Boord elimination afforded several potential CD-ring precursors which can be used in the total synthesis of paclitaxel analogues.
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    An Improved Method for the endo-Fusion of Five-Membered Ring Lactones to the Bornane Ring System (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2507-2511 
    Details
    ISSN: 1434-193X
    Keywords: Camphoracetyl chloride ; Lactols, fused ; Lactones, fused ; Pseudoacid chlorides ; Reagents, stereoselective ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: endo-Fused lactone 3 was obtained in high yield from the camphoracetic acid 2 with thionyl chloride and a subsequent reduction of intermediate 5 with tributyltin hydride. The structure of 5 was elaborated and some aspects of the mechanism of its formation and reactivity were investigated. Lactone 3 serves as key intermediate for lactol 1 which is a useful reagent in racemate resolution and asymmetric synthesis.
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    Synthesis and Characterization of Novel Pyridines and 3,3′-Bridged Bipyridines Using 1,x-Cyclohexanediones (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2609-2615 
    Details
    ISSN: 1434-193X
    Keywords: Supramolecular chemistry ; Domino reactions ; Bipyridines ; 1,x-Cyclohexanediones ; Mannich bases ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A one-pot reaction using 1,x-cyclohexanediones, a Mannich base (or its hydrochloride), and ammonium acetate delivers novel pyridines or 3,3′-bridged bipyridine compounds 8, 16, 18, 20, and 22. This strategy offers a great flexibility in the design of new building blocks, e.g. in supramolecular chemistry and underlines the efficiency of domino reactions.
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    Fluorinated Analogs of Retinoids: Stereocontrolled Synthesis Employing Fluoroisoprenoidal Horner Ylides (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2603-2607 
    Details
    ISSN: 1434-193X
    Keywords: Fluoro analogs of vitamin A ; Horner-Wittig reaction ; Fluoroisoprenoid building blocks ; Stereoselectivity ; Hydrolysis of chlorofluorocyclopropanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An improved method for the preparation of ethyl 2-fluoro-3-methyl-2-butenoate (3) is described. The two stereoisomers [(E)-4 and (Z)-4] obtained after γ-bromination can be separated and can be individually converted into the corresponding diethyl phosphonates. The PO-ylides generated by α-deprotonation of the latter lose their stereochemical integrity by rapid torsional equilibration of the ester tail. Thus, Horner-Wittig reactions accomplished with benzaldehyde and (Z)- or (E)-(β-ionylidene)-acetaldehyde lead inevitably to stereorandomization at the terminal, ethoxycarbonyl-bearing double bond affording (E)- and (Z)-isomers in 50:50 to 15:85 ratios, depending on the reaction conditions. The new double bond, however, is formed with perfect trans-selectivity.
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    Cyclization of 3-Aminoacrylates - Total Synthesis of Pumiliotoxin C and Related Stereoisomeric Compounds (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2641-2646 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Total synthesis/Pumiliotoxin ; PTX-C ; PTX isomers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the synthesis of pumiliotoxin C (1a) and related stereoisomeric compounds 1c-1f. Starting from (+)- or (-)-3-methylcyclohexanone (6a,b), the oxo esters 7a and 7b were prepared. Condensation with (+)- or (-)-3-aminohexanol (8a,b) gave the stereoisomeric 3-aminoacrylates 9a, 9b and 9c. The hydroxy group of the amino-acrylates was transformed into bromide using the tosylate method. Cyclization of the bromides led to unsaturated quinoline ring systems. Finally, decarboxylation and catalytic hydrogenation gave the different cis- and trans-fused stereoisomeric alkaloids of the pumiliotoxin C type. The structures were verified by X-ray analysis.
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    Synthesis of 3,7-Disubstituted 9-Thiatricyclo[3.3.1.03,7]nonane-1,5-dithiol Derivatives and Crystal Structure of Tetramethyl 3(4aH)-Oxo-1,4-dihydrophenanthro[9,10-a]pentalene-1,2,4,4a-tetracarboxylate (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2647-2650 
    Details
    ISSN: 1434-193X
    Keywords: Lawesson's reagent ; Thiolation of cyclic ketones ; Anchimeric effect ; cis-Bicyclo[3.3.0]octane-3,7-diones ; 9-Thiatricyclo[3.3.1.03,7]nonane ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple and efficient approach to the 9-thiatricyclo[3.3.1.03,7]nonane ring system (5) has been found by treating cis-bicyclo[3.3.0]octane-3,7-diones (1) with Lawesson's reagent or phosphorus pentasulfide. When dione 1 is treated with Lawesson's reagent tetramethyl 3(4aH)oxo-1,4-dihydrophenanthro[9,10-a]pentalene-1,2,4,4a-tetracarboxylate (6) is obtained as a by-product as shown by X-ray structural analysis.
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    Synthesis of Chiral 4-(ω-Hydroxyalkyl)pyrazolidin-3-ones by Ring-Chain Transformation of α-Alkylidenelactones with Hydrazines (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2667-2672 
    Details
    ISSN: 1434-193X
    Keywords: Pyrazolidin-3-ones ; Optical activity ; Asymmetric synthesis ; Ring transformation ; Hydrazines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiopure α-alkylidenelactones 7 were prepared by a Wittig reaction from α-bromolactones 4 and chiral aldehydes 6. Compounds 7 react with hydrazines 9 by stereoselective Michael-like addition and ring-chain transformation affording optically active 4-(ω-hydroxyalkyl)pyrazolidin-3-ones 11.
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    A Novel Concept for Transition-Metal-Catalyzed Reactions: Electron Transfer under Buffered Protic Conditions (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2673-2676 
    Details
    ISSN: 1434-193X
    Keywords: Aromatic aldehydes ; Pinacol coupling ; Radical reactions ; Reagent control ; Titanium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel concept for conductingtransition-metal-catalyzed radical reactions that allows highly diastereoselective titanocene-catalyzed pinacol couplings is described.
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    Synthesis of Spirolactones from the Limonene System (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2677-2682 
    Details
    ISSN: 1434-193X
    Keywords: Terpenoid lactones ; Antifeedants ; Limonene ; Claisen rearrangement ; Iodolactonization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four enantiomeric pairs of spirolactones were obtained in a four step synthesis from (+) and (-) limonene. The Claisen rearrangement and iodolactonization were the key steps of the syntheses presented. The structures of products were confirmed by X-ray crystallography of 11, 18b, and 19.
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    Functionalisation of the 1-Phosphanorbornadiene Structure at the C2 Position by Stille Cross-Coupling Reactions (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2683-2687 
    Details
    ISSN: 1434-193X
    Keywords: Phosphole ; Phosphanorbornadiene ; Stille cross-coupling ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of alkynylstannanes with 1-phenyl-3,4-dimethylphosphole at 150 °C affords the corresponding 2-stannyl-1-phosphanorbornadienes (2a, b), in fair yield. Oxidation under mild conditions affords the corresponding phosphane oxides (3a, b), whereas more drastic conditions (H2O2, 15% in toluene at 80 °C) induce the oxidative cleavage of the P-CH2 bond of the bridge to give a bicyclic phosphinate such as 4. Treatement of 4 by iodine leads to a tin → iodine exchange. The X-ray crystal structure analysis of the resulting 1-phospha-2-oxabicyclo[2.2.2]octa-5,7-diene 1-oxide confirms the functionalisation at the α-position and the relief of ring strain taking place upon insertion of oxygen into the P-CH2 bond of the norbornadiene. The 2-stannyl-1-phosphanorbornadiene 1-oxides (3a, b) readily undergo tin → iodine exchange. The resulting 2-iodo derivatives (6a, b) can be cross-coupled with 2-furyl-, 2-thienyl-, 2-pyrrolyl-, phenylethynyl-, and vinyl-tributylstannanes to give the corresponding 2-functional 1-phosphanorbornadiene 1-oxides in excellent yields (80-95%)
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    Stereoselective Intramolecular Hetero Diels-Alder Reactions of Cyclic Benzylidenesulfoxides and DFT Calculations on the Transition Structures (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2733-2741 
    Details
    ISSN: 1434-193X
    Keywords: Asymmetric synthesis ; Density functional calculations ; Cycloadditions ; Dihydropyrans ; Enantioselective oxidations ; Sulfur heterocycles ; Sulfoxides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 4-benzylidene-3-oxo[1,3]oxathiolan-5-ones 13-15, which were derived from the 3-oxo[1,3]oxathiolan-5-ones 9-11 by Knoevenagel condensation with the aldehydes 12, cyclize in an intramolecular hetero Diels-Alder reaction with high yield and excellent endo/exo as well as induced diastereoselectivity to give the hetero Diels-Alder adducts 16-18. The preferred formation of the Knoevenagel products 13-15 with a (Z) configuration was predicted with DFT calculations (B3LYP-6-311+G*) using the model systems 28 and 29. In addition B3LYP-6-31G*/sB3LYP/3-21G(*) calculations on transition structures for the hetero Diels-Alder reaction of 29 and 30 allowed a good correlation with the experimental results, which show that an endo attack of the dienophile syn to the S-O group in 13-15 leads to the main products.
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    Studies on Phosphorus Phthalocyanines and Triazatetrabenzcorroles (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2759-2767 
    Details
    ISSN: 1434-193X
    Keywords: Phosphorus phthalocyanines ; Triazatetrabenzcorroles ; Dihydroxyphosphorus(V) phthalocyanine hydroxides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The previously reported reaction of phthalocyanines [H2(pc)] with PBr3, which was claimed to give a phosphorus(III) phthalocyanine “(PcPIII)”, has been reinvestigated in detail with both unsubstituted and alkyl-substituted phthalocyanines, 1-4. The products exhibit unusual electronic and mass spectra compared to normal phthalocyanines and have been identified as oxophosphorus(V) triazatetrabenzcorroles 5-8. The corresponding dihydroxyphosphorus(V) phthalocyanine hydroxides 9-12 have also been synthesized for the first time by insertion of phosphorus(V) into phthalocyanines and have been characterized in detail. The different reactivities of PBr3 and POX3 (X = Cl, Br) toward phthalocyanines are discussed.
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    A General Synthesis of Disubstituted Rubicenes (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2769-2773 
    Details
    ISSN: 1434-193X
    Keywords: Rubicenes ; Cyclization ; Polycyclic aromatic hydrocarbons ; Arenes ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of novel disubstituted rubicenes 1a-k is described. Starting from 1,5-dichloroanthraquinone and aryllithium reagents 3, the diol adducts 4 are reduced and the resulting diarylanthracenes 5 are cyclized to afford the title compounds in fair to good overall yield.
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    Photochemistry of 9,10-Dicarbonyl-9,10-dihydroanthracene - A Source of 9,10-Dehydroanthracene? (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 57-60 
    Details
    ISSN: 1434-193X
    Keywords: Benzyne ; Dehydroanthracene ; Matrix isolation ; Photochemistry ; Bergman reaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -9,10-Didehydroanthracene (1) is an interesting derivative of p-benzyne that has been subject of several studies. In contrast to an earlier report, the photochemical decarbonylation of 9,10-dicarbonyl-9,10-dihydroanthracene (2) does not lead to 1 but rather to the ring-opened ene-diyne 4. The key intermediate for this reaction is keto carbene 7 which is formed by monodecarbonylation of 2. Carbene 7 is labile towards visible-light irradiation and easily looses the second CO molecule to give 4. Carbene 7 and diyne 4 are characterized by IR and UV/Vis spectra, the IR spectra are compared to calculations at the B3LYP/6-31G(d,p) level of theory.
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    Reversal Diastereofacial Selectivity in the n-Butyllithium Addition to O-Protected N-Trimethylsilylimines of (2S)-Lactal: Enthalpic versus Entropic Contributions (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 61-65 
    Details
    ISSN: 1434-193X
    Keywords: Nucleophilic addition ; Solvent effect ; Reversal of diastereoselectivity ; Temperature effect ; Imines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Commonly observed, but rarely explored, is the possibility of modifying the diastereomeric excess (de%) by means of temperature. A complete reversal in the diastereofacial selectivity could be obtained whenever the diastereoisomers concerned are differentially favored by enthalpy and entropy. The enthalpic or entropic dominance of a diastereoisomer depends greatly on the reaction solvent used.
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    Syntheses of Donor-Acceptor-Substituted 2,6-Stellanes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 73-81 
    Details
    ISSN: 1434-193X
    Keywords: Donor-acceptor systems ; Cage compounds ; Stelladione ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A number of condensations could be carried out using tricyclo[3.3.0.03,7]octane-2-one (stellanone, 4) and tricyclo[3.3.0.03,7]octane-2,6-dione (2,6-stelladione, 5) as starting materials. The components for condensations were 2-trimethylsilyl-1,3-dithiane (6), 1,1-bis(trimethylsilyl)-1H-cyclopropa[b]naphthalene (7), its 3,6-dimethoxy-substituted analogue 8, fluorene (12), xanthene (13), diethyl malonate (14), and malononitrile (15). The condensation reactions with 5 yielded mono- and disubstituted products, among them were the donor-acceptor-substituted 2,6-stellanes 33-35. The structures of 18 (prepared from stellanone and fluorene), 19, 24, 27, 31 and 32 (synthesized by condensation of 2,6-stelladione and 2-trimethylsilyl-1,3-dithiane and malononitrile, respectively) were determined by X-ray crystallography.
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    Synthesis of ω-Nitro Acids and ω-Amino Acids by Ring Cleavage of α-Nitrocycloalkanones (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 87-90 
    Details
    ISSN: 1434-193X
    Keywords: Water ; α-Nitrocycloalkanones ; ω-Nitro acids ; Surfactant ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The reaction of various α-nitrocycloalkanones 1 with aqueous 0.05 M NaOH, at 80 °C, in the presence of cetyltrimethylammonium chloride (CTACl) as a cationic surfactant, produces ω-nitro acids 2 in good yields. Reduction of the latter with HCOONH4/Pd-C, in methanol, at 80 °C affords ω-amino acids 3. The synthesis of methyl 9-oxodecanoate (8) is also reported.
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    On the Selective O-Alkylation of Ambident Nucleophiles - The Synthesis of Thiohydroxamic Acid O-Esters by Phase-Transfer Reactions (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 97-106 
    Details
    ISSN: 1434-193X
    Keywords: O-Alkylation ; Ambident nucleophile ; Thiazolethione ; Thiohydroxamic acid ; Phase-transfer reaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -O-Alkylation of cyclic thiohydroxamic acids 1 and 3-5 has been studied with a view to developing an efficient method for the synthesis of N-(alkoxy)pyridine-2(1H)-thiones and N-(alkoxy)thiazole-2(3H)-thiones. Four issues have been addressed and the following conclusions can be drawn: (i) Thiones 1 and 5 exist as O-H acids in the solid state. (ii) According to NMR investigations (1H, 13C), the thione structures should be largely retained in CDCl3, [D6]DMSO, and CD3OD solutions of acids 1, 3-5, as is also the case for pyridinethione salts 2a-h. (iii) O-Alkylation of pyridinethione salts occurs in competition with S-alkylation. Selective O-alkylation is however possible, if thiohydroxamate salts with large countercations, such as M = NBu4, are treated with hard alkylating reagents in polar aprotic media. (iv) As tetrabutylammonium thiohydroxamates, such as 2f, are highly useful in the synthesis of cyclic thiohydroxamic acid O-esters, we have developed an efficient protocol for the preparation of N-(alkoxy)pyridine-2(1H)-thiones directly from acid 1 using phase-transfer conditions (alkyl halide or sulfonic acid ester, CH3CN, K2CO3, Bu4NHSO4). This method has proved particularly successful for the synthesis of N-(alkoxy)thiazole-2(3H)-thiones 11, 20-28, which were obtained in yields of up to 87%.
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    Palladium(0)-Catalyzed Asymmetric Synthesis of 1,2,3,4-Tetrahydro-2-vinylquinoxalines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 129-134 
    Details
    ISSN: 1434-193X
    Keywords: Tetrahydro-2-vinylquinoxaline ; Cyclization ; Palladium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Reaction of (Z)-1,2-bis(methoxycarbonyloxy)but-2-ene (2) with various N,N-bis(arylsulfonyl)-o-phenylenediamines 1 was catalyzed by a palladium complex associated with chiral ligands to give optically active 1,4-bis(arylsulfonyl)-1,2,3,4-tetrahydro-2-vinylquinoxalines 3 with up to 62% ee. The use of (S)-MeOBIPHEP as the chiral ligand and N,N-bis(p-tolylsulfonyl)-o-phenylenediamine (1i) as the nucleophile led to the highest ee at 25 °C, regardless of the solvent used. The enantioselectivity of the cyclization is strongly affected by the nature of the substituents at the nitrogen atom.
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    Stereoselective Synthesis of Enantiomerically Pure β-Fluoroalkyl γ-Butyrolactones by Sulfoxide-Directed Lactonization (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 111-115 
    Details
    ISSN: 1434-193X
    Keywords: Fluorine ; Lactones ; Annulation ; Ketene ; Sulfoxides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Enantiomerically pure α,α-dichloro β-fluoroalkyl γ-p-tolylthio γ-butyrolactones trans-6a-c have been obtained with excellent stereocontrol (〉 98:2) and enantiomeric purity (〉 98:2) by sulfoxide-directed lactonization (Marino's annu-lation reaction) of β-fluoroalkyl vinyl sulfoxides (R)-(E)-5a-c with dichloroketene. Highly chemoselective dechlorination and desulfurization reactions performed on trans-6c efficiently provided the β-chlorodifluoromethyl γ-butyrolactone (S)-8c, the absolute stereochemistry of which was determined by X-ray diffraction analysis of its γ-p-tolylthio precursor (2R,3S)-7c.
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    Reaction of Nitrosobenzene with 4-Methoxy-N-methyleneaniline (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 141-143 
    Details
    ISSN: 1434-193X
    Keywords: Nitrosobenzene ; 4-Methoxy-N-methyleneaniline ; 1,3,5-Tris(4-methoxyphenyl)-1,3,5-triazinane ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A 1:1 adduct produced in the reaction of nitrosobenzene (2) with 1,3,5-tris(4-methoxyphenyl)-1,3,5-triazinane (3) has been shown by X-ray diffraction structure analysis to be the N′-(4-methoxyphenyl)-N-phenyl-N-oxyformamidinium species 5.
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    A New Diastereoselective Synthesis of anti-α-Alkyl α-Hydroxy β-Amino Acids (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 155-161 
    Details
    ISSN: 1434-193X
    Keywords: Alkylation ; Oxazolines ; anti-α-Alkyl α-hydroxy β-amino acids ; Lithium dianion ; Penicillin G acylase ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -As part of an ongoing project concerning the synthesis of enantiomerically pure α-hydroxy β-amino acids, we have now developed a general strategy allowing the synthesis of anti-α-alkyl α-hydroxy β-amino acids. Our procedure involves the intermediate formation of trans-oxazolines, which are alkylated at C-5 with good to high diastereoselectivity and then hydrolysed under mildly acidic conditions, affording in quantitative yield the corresponding hydroxy amides. The starting (R)-3-amino-3-phenylpropanoic acid and (S)-3-aminobutanoic acid were obtained in enantiomerically pure form by selective enzymatic hydrolysis of the corresponding phenylacetylamides with penicillin G acylase.
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    Palladium(0)-Catalyzed Reaction of Acidic Anilines with (Z)-2-Butene-1,4-diyl Dicarbonate - Preparation of N-Aryl-4-vinyloxazolidin-2-ones (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 181-186 
    Details
    ISSN: 1434-193X
    Keywords: Palladium catalysis ; Homogeneous catalysis ; Anilines ; Alkylation ; Oxazolidinones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Palladium-catalyzed reaction of acidic anilines with (Z)-2-butene-1,4-diyl dicarbonate affords N-aryl-4-vinyloxazolidin-2-ones. The success of the reaction depends on the acidity of the aniline and requires in situ conversion of the dicarbonate into carbamate carbonate by nucleophilic attack of the aniline conjugate base followed by palladium-catalyzed intramolecular cyclization.
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    Substituent Effects on the Vinylcyclopropane-Cyclopentene Rearrangement - A Theoretical Study by Restricted and Unrestricted Density Functional Theory (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 215-220 
    Details
    ISSN: 1434-193X
    Keywords: Density functional calculations ; Vinylcyclopropane-cyclopentene rearrangement ; [1,3]-Sigmatropic shift ; Biradical-like transition structure ; Substituent effects ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The effect of donor substitution by the hydroxy group and of acceptor substitution by the cyano group on the activation energies of the vinylcyclopropane-cyclopentene rearrangement was calculated by the spin-restricted RB3LYP/6-31G* method for reactant structures and by the spin-unrestricted UB3LYP/6-31G* method for transition structures. The activation energies of the rearrangement of hydroxy- and cyano-substituted vinylcyclopropanes are very similar for substitution in the same position. In agreement with earlier findings the substituent effects on the activation energies are closely connected with the radical stabilizing properties of the substituents. As indicated by singlet/triplet splitting energies, the transition structures are essentially biradicaloid. In spite of spin pairing in the transition structure the substituent effects on bond lengths and on stabilization energies are very similar to those of the free radicals corresponding to the two radical substructures. Thus, the transition structures may be considered, in good approximation, as structures consisting of two weakly interacting radicals.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98349_s.pdf or from the author.
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    Syntheses and Reactions of 1-Amino-2,2-dialkylcyclopropane-1-carbonitriles and -carboxamides - Potential Precursors of ACC Derivatives (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 239-250 
    Details
    ISSN: 1434-193X
    Keywords: Cyclopropanes ; Rearrangements ; Cyanohydrins ; Schiff bases ; Small ring systems ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The direct cyclization of 2-amino-4-chloro-3,3-dimethylbutanenitrile with potassium tert-butoxide in THF afforded 1-amino-2,2-dimethylcyclopropane-1-carbonitrile and a dimerization product. Various new cis- and trans-1-(tert-butylamino)-2-benzyl-2-methylcyclopropane-carbonitriles and© the corresponding cyclopropanecarboxamides have been synthesized, with focus on the isolation of the pure stereoisomeric cyclopropanecarboxamides. The relative configuration of the stereoisomers was established by X-ray crystallographic analysis of one of the model compounds. A new route to the latter functionalized cyclopropanes was developed by reaction of 1-methoxycyclopropylamines with potassium cyanide. Some remarkable rearrangements of 1-aminocyclopropane-1-carbonitriles into azetidine and oxazine derivatives via Favorskii-derived intermediates are reported. Various aspects of the chemistry of geminally functionalized cyclopropanes are discussed.
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    Regio- and Stereoselective Synthesis of Vinylallenes by 1,5-(SN′′)-Substitution of Enyne Acetates and Oxiranes with Organocuprates (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 267-275 
    Details
    ISSN: 1434-193X
    Keywords: Vinylallenes ; Organocuprates ; Substitution ; Stereoselective synthesis ; Copper catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Enyne acetates 2, 4, 6, and 8, as well as enyne oxiranes 10, with different substitution patterns react with organocuprates regioselectively under 1,5-(SN2′′)-substitution to provide vinylallenes 11 and 12. With lithium dimethylcuprate, reduced vinylallenes originating from a (formal) transfer of a hydride ion to the substrate are formed in some cases. The products are usually obtained as mixtures of (E/Z)isomers; however, pure (E)-vinylallenes are formed occasionally. The 1,5-substitutions can also be carried out with catalytic amounts of copper reagents. The reaction of chiral enyne acetate (S)-2a with tBu2CuLi · LiCN proceeds enantioselectively, so that this transformation constitutes a new case of remote stereocontrol.
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    Reactions of the Hydrofluoroborate Salts of Open-Chain Analogues of Reissert Compounds with Some α,β-Ethylenic Esters (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 297-303 
    Details
    ISSN: 1434-193X
    Keywords: Nitrogen heterocycles ; Open-chain analogue of Reissert compound ; Hydrofluoroborate salts ; α,β-Ethylenic esters ; 1,3-Dipolar cycloaddition ; Azomethine ylide ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The reaction of the hydrofluoroborate salt of an open-chain analogue of a Reissert compound with some α,β-ethylenic esters does not give a [4 + 2] cycloadduct, as previously described in the case of ethyl acrylate. The reaction starts with a 1,3-dipolar cycloaddition of a münchnone imine 5c, d. The [3 + 2] cycloadducts 13 evolve via a rearrangement-condensation sequence to give a substituted 2-pyridone derivative 18 or 19. The proposed mechanism has been verified by the isolation and structural X-ray analysis of some compounds of the reaction sequence.
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    EPC-Synthesis of β-Amino Acid Derivatives through Lithiated Hydropyrimidines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 335-360 
    Details
    ISSN: 1434-193X
    Keywords: 2-tert-Butylhydropyrimidinones ; 3-Aminocarboxylic acid derivatives ; Cyclic imino esters ; Lithium enaminates ; Alkylations ; β-Amino acids ; Asymmetric synthesis ; Kinetic resolution ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Racemic and enantiopure 2-tert-butyltetrahydropyrimidinones (from pivalaldehyde and 3-aminocarboxylic acids) are converted to Alloc-, Boc-, and Z-protected cyclic imino esters (7-10, Schemes 2-4). These are deprotonated to Li enaminates (K, L). Reactions with electrophiles (prim., sec. alkyl, allyl, benzyl, propargyl halides, aldehydes, imines, enoates) give good yields and are highly diastereoselective (products 11-42, Schemes 5-10). A two-step cleavage (removal of protecting group and hydrolysis) under very mild conditions converts the heterocyclic products to α-branched β-amino acid methyl esters (43-61, Schemes 11-13). The structure of the products is determined by NMR spectroscopy (Figure 1), by chemical correlation (Scheme 14), and by X-ray analysis (Figure 2, 3, 7, Table 1). A structure of the Li enaminates is proposed (Figure 4). Mechanistic models are derived for the reactions occurring with formation of two stereogenic centers with relative topicity like (Figures 5, 6).
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    A Unified Synthetic Strategy for the Indolopyridine Alkaloid Group (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 373-378 
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    ISSN: 1434-193X
    Keywords: Alkaloids ; Cross-coupling ; N-Heterocycles ; Palladium ; Synthesis design ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Thermal or acetyl chloride induced cyclization of bromoenamide 10 affords the pentacyclic derivative 12 with high yield and regioselectivity. From this common synthetic intermediate, palladium-catalyzed reactions allow the total synthesis of indolopyridine alkaloids 1-6.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98332_s.pdf or from the author.
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    Conformational Preferences of Peptides Containing Reverse-Turn Mimetic Bicyclic Lactams: Inverse γ-Turns versus Type-II′ β-Turns - Insights into β-Hairpin Stability (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 389-400 
    Details
    ISSN: 1434-193X
    Keywords: Reverse-turn mimics ; γ-Turns ; β-Turns ; β-Hairpins ; NMR spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The solid-phase synthesis and characterization of a series of peptides (3-9), containing reverse-turn mimetic bicyclic lactams (1a, 1b), was reported in the preceding paper. The bicyclic lactams (1a, 1b) possess high structural similarity to the two central residues of a β-turn. The conformational preferences of the constrained peptides have been investigated by NMR spectroscopy and IR spectroscopy. Our experimental results have been complemented by computer modelling studies and show that the constrained peptides (3-9) form an inverse γ-turn or a type-II′ β-turn through intramolecular hydrogen bonding, depending on the nature of the reverse-turn mimic. In N-acetylated tetrapeptide mimics incorporating the two different bicyclic lactams (a series and b series), H5 is available for either a γ-turn (7-membered ring with the carbonyl group of the bicyclic lactam) or a β-turn (10-membered ring with the carbonyl group of residue 2), as shown in Figures 7 and 9. The a series incorporating the (5,7)-bicyclic lactam predominantly induces the γ-turn conformation, while the b series incorporating the (5,6)-bicyclic lactam can promote either a γ-turn or a β-turn conformation, with the β-turn usually being preferred and with varying degrees of β-hairpin formation.
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    Deprotonation of Oxazolinyloxiranes: Formation of Substituted Acyloxiranes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 409-417 
    Details
    ISSN: 1434-193X
    Keywords: Deprotonation ; Oxiranyloxazolines ; Oxazolinyloxiranyllithium compounds ; Oxazolidines ; Acyloxiranes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Deprotonation of oxazolinyloxiranes 1a, 1h, and 1k with sBuLi/TMEDA at -100 °C in Et2O furnishes oxazolinyloxiranyllithium compounds[1]1b, 1i, and 1l which are stable at low temperature and can be trapped with electrophiles to give substituted oxiranes 1c-1g and 1j. The reaction of 1b with aldehydes produced diastereomers syn (2a-d) and anti (3a-d). Oxiranyllithium 1i from trans-1-(4,4-dimethyl-2-oxazolinyl)-2-p-tolylepoxyethane (1h) was found to be configurationally stable while oxiranyllithium 1l, generated from the cis isomer 1k, was not. Oxazolinylepoxides 1d, 1j, and 1m could be deblocked to acyloxiranes 5a-e through oxazolidines 4a-e.
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    N-Substituted 1-Aminoindoles from Electrogenerated N-Substituted 2-(ortho-Nitrosophenyl)ethylamines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 419-430 
    Details
    ISSN: 1434-193X
    Keywords: Electrochemistry ; Electrosynthesis ; Nitrosobenzenes ; Nitrogen heterocycles ; 1-Aminoindoles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -An electrochemical methodology offering efficient access to N-alkyl- and N-aryl-substituted 1-aminoindoles has been developed. N-Substituted 2-(ortho-nitrosophenyl)ethylamines, electrogenerated in a “redox” flow cell, undergo intramolecular cyclization to hydrocinnoline-type intermediates. Under slightly basic conditions, these undergo spontaneous ring-contraction to produce the N-substituted heterocycles in good yields. The reactions have been studied in slightly acidic and slightly basic aqueous alcoholic media.
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    Synthesis of Enantiopure β- and γ-Amino Alcohols from Homochiral α- and β-Aminoacylsilanes as Stable Synthetic Equivalents of α- and β-Amino Aldehydes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 437-445 
    Details
    ISSN: 1434-193X
    Keywords: Aminoacylsilanes ; Amino aldehydes ; Amino alcohols ; Allylation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A practical route is described for the synthesis of enantiopure β- and γ-amino alcohols with two stereocenters, starting from homochiral α- (1 and 5) and β- (13 and 16) -aminoacylsilanes, and involving stereoselective addition of allylmetal compounds and subsequent stereospecific protiodesilylation of the adducts. The degree of diastereoselectivity achieved in the nucleophilic addition step depends on both the nitrogen-protecting group and the reagents used. Diastereomeric excess (de) values equal to or higher than 98% were obtained in the TiCl4-promoted allylation of the N-Pht-aminoacylsilanes 1 and 13 and of the N-Ts-aminoacylsilane 5 with allyltrimethylsilane. Lower de values were obtained in the Sc(OTf)3-catalyzed allylation of 5 with tetraallyltin and in the additions of both allyltrimethylsilane and tetraallyltin to the N-Ts-β-aminoacylsilane 16. Protiodesilylation of the adducts, leading to the β- and γ-amino alcohols, was accomplished with TBAF, except in the case of the adducts obtained from 5. For these, a preliminary removal of the tosyl group was necessary, which was accomplished with simultaneous desilylation by treatment with Na in liquid ammonia.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98342_s.pdf or from the author.
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    Diastereoselective Intramolecular meta Photocycloaddition of Side-Chain-Substituted 5-(2-Methoxyphenyl)pent-1-enes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 463-470 
    Details
    ISSN: 1434-193X
    Keywords: meta Photocycloaddition ; Photochemistry ; Steric hindrance ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Irradiation of a series of 5-(2-methoxyphenyl)pent-1-enes substituted with a hydroxy or trimethylsilyloxy group at the α-, β-, or γ-position of the side-chain yields in all cases meta photocycloadducts, in which the configuration at the substituted carbon atom is mainly endo. This indicates that the diastereoselectivity originates from minimization of steric interactions between the side-chain substituent and the ortho-methoxy group at the arene unit. Hydrogen bonding does not seem to be involved. The introduction of the side-chain substituents also influences the regioselectivity of the addition: The linear to angular adduct ratios are significantly increased compared to the case of the parent compound.
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    5-Aza-7-deaza-2′-deoxyguanosine: Oligonucleotide Duplexes with Novel Base Pairs, Parallel Chain Orientation and Protonation Sites in the Core of a Double Helix (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 485-496 
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    ISSN: 1434-193X
    Keywords: 5-Aza-7-deaza-2′-deoxyguanosine ; Oligonucleotides ; Parallel DNA ; Protonated base pairs ; Tm values ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Oligonucleotides containing 5-aza-7-deaza-2′-deoxyguanosine (1) were synthesized. Solid-phase synthesis was performed with the phosphonate 15 or the phosphoramidite 5. The amino-unprotected phosphonate 4 was also employed. Hybridization studies of oligonucleotides containing 1 resulted in new base pairs leading to duplexes with parallel (ps) or antiparallel (aps) chain orientation. Among those with parallel chains a stable “purine-purine” base pair was observed between 5-aza-7-deazaguanine and guanine or 7-deazaguanine. Antiparallel stranded duplexes are formed when 5-aza-7-deazaguanine pairs with cytosine. This base pair has only two hydrogen bonds under neutral conditions but is stabilized by a third one in acidic medium. A new base pair is also detected between the base of 1 and isoguanine (neutral medium).
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    Polar and Steric Substituent Effects in 5-exo-trig Cyclizations of 1-Aryl-4-penten-1-oxyl Radicals (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 523-523 
    Details
    ISSN: 1434-193X
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -By mistake wrong concentrations were given in the footnote of Table 1 and in the Discussion. Instead of c0 = 1.2 M read c0 = 0.12 M if 2-naphthalenethiol was used as hydrogen donor and instead of c0 = 1.8 M read c0 = 0.18 M if Bu3SnH was used to trap photoproducts. In Table 2 relative rate constants of radical 2d refer to radical 2e and vice versa as correctly stated in the Discussion. In the Experimental Section (Iodocyclization) read 2.25 g (8.86 mmol) of iodine instead of 2.25 g (1.10 mmol) of iodine.
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    Arylboron Compounds as Acid Catalysts in Organic Synthetic Transformations (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 527-538 
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    ISSN: 1434-193X
    Keywords: Tris(pentafluorophenyl)borane ; Diarylborinic acid ; Arylboronic acid ; Chiral arylboron catalyst ; Lewis acid ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Arylboron compounds, ArnB(OH)3-n (n = 1-3), bearing electron-withdrawing aromatic groups such as triarylboranes, diarylborinic acids, and arylboronic acids represent a new class of air-stable and water-tolerant Lewis acid or Brønsted acid catalysts in organic synthesis. In particular, while tris(pentafluorophenyl)borane has primarily been used as a co-catalyst in metallocene-mediated olefin polymerization, its potential as a Lewis acid catalyst for organic transformation is now much more extensive. Diarylborinic acids and arylboronic acids have shown themselves to be powerful tools in the design of chiral boron catalysts. This article provides a comprehensive summary of the organic transformations catalyzed by arylboron compounds as acids.
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    2D-NMR-Guided Constitutional Analysis of Organic Compounds Employing the Computer Program COCON[#] (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 573-577 
    Details
    ISSN: 1434-193X
    Keywords: Structure elucidation ; Constitutional analysis ; Natural products ; HMBC ; Computational chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The computer program COCON is introduced as a tool for the comprehensive structure elucidation of unknown organic compounds. In particular, structural proposals made on the basis of the molecular formula and of 2D-NMR experiments can be analyzed for the existence of alternative constitutions being in agreement with the same data set. The computational speed grounds on the evaluation of ambiguous long-range connectivity information during the process of structure generation. The data set experimentally obtained for the marine natural product oroidin (1) was selected, because proton-poor compounds usually cause uncertainties in NMR-based structure determinations. The calculation results encourage to move from the experience-based analysis of NMR chemical shifts or of MS fragmentations to the automated evaluation of routinely available connectivity information.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98241_s.pdf or from the author.
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    3,5-Dimesityl-1,2,4-oxadiphosphole - Synthesis and Reactivity of a Novel Heterocycle (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 587-595 
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    ISSN: 1434-193X
    Keywords: Phosphaalkenes ; Heterodiphospholes ; Cycloadditions ; Phosphaalkyne cyclooligomers ; Phosphorus-carbon cage compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The first synthesis of a 1,2,4-oxadiphosphole 6 has been achieved by vacuum thermolysis of mesitylphosphaalkene 5. The novel heterocycle 6 exhibits an enormous potential for cycloaddition reactions, which predominantly proceed selectively at low temperatures. Compound 6 undergoes addition with two equivalents of phosphaalkynes 10 by a [4+2] cycloaddition/homo Diels-Alder reaction sequence to form novel oxatetraphosphadeltacyclenes 12 and 13. Tetrachloro-o-benzoquinone (14) undergoes a selective [4+1] cycloaddition with 12 and 13 leading to the spirocyclic products 15 and 16 containing λ5-phosphorus atoms. Treatment of the oxadiphosphole 6 with dimethyl acetylenedicarboxylate (17) provides the first access to a 1,2-oxaphosphole 18, which is formed after an initial [4+2] cycloaddition followed by a retro Diels-Alder reaction. An unexpected reaction of 6 is observed with tri-tert-butylazete (20) furnishing a new polycyclic system (→ 21).
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    Synthesis of 1β-Methylcarbapenem Antibiotic Precursors by Cyclization Using π-Allylpalladium Complexes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 621-626 
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    ISSN: 1434-193X
    Keywords: 1β-Methylcarbapenems ; Palladium ; Ruthenium ; Catalysis ; Cyclizations ; Stereoselective hydrogenation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -An efficient diastereoselective multi-step synthesis of bicyclic 1β-methylcarbapenem antibiotic precursors has been developed, starting from the commercially available 4-acetoxyazetidin-2-one 4. Chiral ruthenium catalysts are used in the hydrogenation step to control the β-stereochemistry at the 1-position, and a π-allylpalladium ring-closure strategy is used to form the functionalized carbapenem skeleton.
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    Oligo-2,6-naphthylenevinylenes - New Building Blocks for the Preparation of Photoluminescent Polymeric Materials (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 643-651 
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    ISSN: 1434-193X
    Keywords: Oligomers ; Synthesis design ; Substituent effects ; Luminescence ; Cyclic voltammetry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Synthetic strategies towards appropriate symmetric and unsymmetric functionalization of the naphthalene ring are presented. By means of Knoevenagel and Wittig condensation reactions new fluorescent, differently functionalized oligo(2,6-naphthylenevinylene)s have been synthesized, the presence of terminal aldehyde or bromine substitution opening the way to the incorporation of the fluorescent trimers in a variety of polymeric materials. The effect of substituting the phenylene ring by the more bulky dialkoxynaphthalene system in arylenevinylene-type materials is studied from the structural point of view and the possibility to tune the emission color and the electron affinity through the introduction of naphthylenevinylene and cyano-substituted naphthylenevinylene units is also investigated.
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    New Type of Skipped Oligoaziridines: Synthesis of New Fatty AcidDerivatives Containing Aziridine Functions (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 661-664 
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    ISSN: 1434-193X
    Keywords: Aziridines ; N-Heterocycles ; Fatty acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The first successful preparation of the aziridines methyl cis-9,10;cis-12,13-diepiminooctadecanoate (3) derived from linoleic acid, and methyl cis-9,10;cis-12,13;cis-15,16-triepiminooctadecanoate (6) derived from linolenic acid, is reported. Remarkably, the bis- and trisaziridine were obtained in a reaction sequence that consists of only two steps, using technically pure methyl esters of epoxidized sunflower and linseed oil. The conversion of methyl 9,10;12,13-diepoxyoctadecanoate (1), with sodium azide and ammonium chloride in ethanol in the presence of water, yielded the new diazidodihydroxy compound methyl 9(10),12(13)-diazido-10(9),13(12)-dihydroxyoctadecanoate (2) in the first step. 2 was obtained as a regioisomeric mixture. The reaction of 2 with triphenylphosphane led to the bisaziridine 3. The analogous conversion of methyl 9,10;12,13;15,16-triepoxyoctadecanoate (4), via the new triazidotrihydroxy compound methyl 9(10),12(13),15(16)-triazido-10(9),13(12),16(15)-trihydroxyoctadecanoate (5), afforded trisaziridine 6.
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    Novel Ligands for the Separation of Trivalent Lanthanides and Actinides - Tetrakis(phosphane sulfide) and -(phosphinic acid) Cavitands (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 665-674 
    Details
    ISSN: 1434-193X
    Keywords: Cavitands ; Nuclear waste ; Actinide/lanthanide separation ; Solvent extraction ; Sulfur atoms ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Cavitands with phosphane sulfide moieties 4 and 8a,b were prepared in good yields from their phosphane oxide analogues, as more stable alternatives for the dithiophosphinic acids used at present. The cavitands 7a and 7b with flexible butoxyphosphane oxide ligating sites are more efficient than cavitand 3 having rigid methylphosphane oxide groups as was studied with EuIII picrate extractions. Due to the absence of an ionic functionality in the phosphane sulfides 4 and 8a,b AmIII and EuIII are not extracted, not even in the presence of synergents (e.g. TBP, TOPO, HDNNS). Cavitand 10 with phosphinic acid groups efficiently extracts EuIII in 1:1 or 2:1 complexes, depending on the metal-to-ligand concentration ratio (extraction constants Kex1 = 3.9·10-5M2 and Kex2 = 1.9·102M, respectively). Furthermore, in the case of 10 EuIII is preferentially extracted over AmIII with a separation factor SEu/Am up to 5.
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    Preparation of 2,3,5-Tri-O-benzyl-4-thio-L-arabino-furanosides and the Corresponding 4′-Thionucleoside Analogues (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 691-696 
    Details
    ISSN: 1434-193X
    Keywords: Carbohydrates ; 4-Thiofuranosides ; Nucleosides ; Reaction mechanisms ; NOE measurements ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -1-O-Acetyl-2,3,5-tri-O-benzyl-4-thio-L-arabino-furanose (9) has been prepared from D-xylose via the 1,4-dithio-L-arabino-furanoside 8. The crucial step of the reaction, i.e. the intramolecular cyclization of the open-chain dithioacetal 5, has been achieved in a yield of 90% by applying tetrabutylammonium iodide as promoter. Reaction of 9 with bis(trimethylsilyl)uracil or -thymine led to the benzyl derivatives 12 and 13 from which the deprotected 4′-thionucleoside analogues 14 and 15 have been prepared by debenzylation with boron tribromide.
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    100 Years of Baeyer-Villiger Oxidations (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 737-750 
    Details
    ISSN: 1434-193X
    Keywords: Baeyer-Villiger oxidation ; Ketones ; Monopersulfate ; Peracids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -In the present review, we report the discovery of the formation of esters and lactones by oxidation of ketones with a peroxide derivative, namely the Baeyer-Villiger reaction. This reaction was first reported by Adolf von Baeyer and Victor Villiger a century ago in 1899, just one year after the oxidant they used (KHSO5) has been described. Furthermore, Baeyer and Villiger established the composition of this new inorganic peroxide and showed that its instability was the reason of a controversy between several European chemists between 1878 and 1893. For the first 50 years the mechanism of the Baeyer-Villiger reaction was a matter of debate. A side product, 1,2,4,5-tetraoxocyclohexane, was ruled out as an intermediate in the ester formation by Dilthey. Criegee postulated a nucleophilic attack of the oxidant on the carbonyl group. This mechanism was confirmed by von E. Doering by a labeling experiment with [18O]benzophenone. The rearrangement step occurs with retention of the stereochemistry at the migrating center. The competitive migration and the rate-determining step are also discussed in this review.
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    Transferase Activity of a β-Glycosidase from Thermus thermophilus: Specificities and Limits - Application to the Synthesis of β-[1→3]-Disaccharides (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 757-763 
    Details
    ISSN: 1434-193X
    Keywords: Transglycosylation ; Glycosidases ; Thermus thermophilus ; Carbohydrates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The aim of this paper is to test the ability of a β-glycosidase from Thermus thermophilus to catalyse transglycosylation reactions in the presence of nitrophenyl glycosides as donors and other monosaccharides as acceptors. Our results show that this enzyme is able to induce such reactions either with nitrophenylgalactosides, -glucosides and -fucosides. With the two former donors, the autocondensation of the donor, which thus acts also as an acceptor, is faster than the transglycosylation with other acceptors. Furthermore, as the regioselectivity of the reactions is mainly of the β-[1→3] type, good yields are obtained for the synthesis of 2-nitrophenyl-β-D-galactopyranosyl-[1→3]-β-D-galactopyranoside and 2-nitrophenyl-β-D-glucopyranosyl-[1→3]-β-D-glucopyranoside. Conversely, in the presence of p-nitrophenylfucoside, the autocondensation is very limited, and with methyl-α-D-galactoside as an acceptor, the regioselectivity is mainly of the β-[1→6]-type resulting in the synthesis of methyl-β-D-fucopyranosyl-[1→6]-α-D-galactopyranoside.
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    Reduction of Acetylenic Compounds to (E)-Olefins by Alkali Metals - An Investigation of the Scope (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 775-779 
    Details
    ISSN: 1434-193X
    Keywords: Monoynes ; Polyynes ; Alkali metals ; Liquid NH3 ; Hexamethylphosphoric triamide ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Efficient procedures have been developed for the stereospecific reduction by alkali metals of disubstituted acetylenes with long carbon chains. Acetylenes containing two or more (isolated) triple bonds are reduced considerably more easily than are monoynes.
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    Synthesis of Enantiopure o-Hydroxybenzylamines by Stereoselective Reduction of 2-Imidoylphenols: Application in the Catalytic Enantioselective Addition of Diethylzinc to Aldehydes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 805-811 
    Details
    ISSN: 1434-193X
    Keywords: Aminophenols /Asymmetric synthesis ; C-C coupling ; Reductions ; Conformation analysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Enantiopure o-hydroxybenzylamines 2a-i were synthesized by diastereoselective reduction of the 2-imidoylphenols (R)-1a-i. Conformational analysis enabled the assignment of the absolute configurations of compounds 2a-i. The accessible o-hydroxybenzylamine (R,R)-2h serves as an effective catalyst precursor for highly enantioselective addition of diethylzinc to aliphatic and aromatic aldehydes. This pathway represents a practical and operationally very simple methodology for the enantioselective synthesis of both the enantiomers of secondary alcohols 7a-f.
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    Cyclialkylation of Arylalkyl Epoxides with Solid Acid Catalysts (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 837-846 
    Details
    ISSN: 1434-193X
    Keywords: Friedel-Crafts reaction ; Hydroxyalkylation ; Aromatics ; Epoxides ; Zeolites ; Clays ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Solid acids, such as zeolites and clays, catalyse the intramolecular hydroxyalkylation (cyclialkylation) of several arylalkyl epoxides in moderate to excellent conversions and selectivities. The use of solid acids in these cyclialkylations provides a cleaner, better alternative to conventional Lewis and Brønsted acids, enabling a more facile workup of reaction mixtures and, in several cases, better selectivities.
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    Phosphorylating Power of Red Phosphorus towards Aldehydes in Basic and in Acidic Media (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 861-868 
    Details
    ISSN: 1434-193X
    Keywords: Red phosphorus ; Phosphane PH3 ; Phosphorylations ; Ultrasound irradiation ; Redox chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The reactivity of red phosphorus towards aldehydes was investigated under basic and acidic media. It was demonstrated that the real phosphorylating agent involved in the reaction was phosphane (PH3) in basic media, and hypophosphorous acid (H3PO2) in acidic media. A convenient one-pot synthesis of (α-hydroxyalkyl)phosphinic acids from red phosphorus and aldehydes in basic media was realized under sonication. The same reaction under acidic media in the presence of hydriodic acid led to the corresponding phosphonic acids. The (α-hydroxyalkyl)phosphinic acids were readily prepared under sonication from hypophosphorous acid and aldehydes in the presence of catalytic amounts of hydrochloric acid. The mechanism of the addition reaction of PH3 to benzaldehyde was elucidated and shows the complexity of the reaction as a function of the experimental conditions.
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    A New Approach to Erythrinanes through Pummerer-Type Cyclization (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 909-915 
    Details
    ISSN: 1434-193X
    Keywords: Erythrina alkaloids ; Nitrogen heterocycles ; Nitro aldol reaction ; Michael addition ; Pummerer reaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A successful new strategy for the synthesis of erythrinanes is reported. (Nitromethyl)arene derivative 16 was condensed with aldehyde 17 to give nitro aldol 19. After removal of the hydroxy group, the subunits 26a,b, containing the erythrinane rings A and D, were formed by intramolecular Michael addition. Reduction of the nitro function, followed by cyclization of the resulting amino group with the appended acetate group afforded the bicyclic lactams 29a,b, bearing an angular aryl group. Two-carbon elongation at the nitrogen atoms of 29a and 29b by means of hetero Michael addition of methyl phenyl sulfoxide, followed by Pummerer-type cyclization, gave cis- and trans-11-phenylthioerythrinan-8-ones 35a and 35b, respectively. Reductive desulfurization at C-11 furnished the desired erythrinan-8-ones 39a and 39b in 8 steps from 16.
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    Synthesis, X-ray Structure Analysis and Topochemical Photopolymerization of Substituted 1,6-Bis(2,5-dimethoxyphenyl)hexa-2,4-diynes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 917-922 
    Details
    ISSN: 1434-193X
    Keywords: Crystal engineering ; Diynes ; Photochemistry ; Solid-state chemistry ; Polymers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The 1,6-bis(2,5-dimethoxyphenyl)hexa-2,4-diynes 4a-c were obtained from the corresponding 2,5-dimethoxybenzenes 1 by bromination followed by a copper-catalyzed Grignard reaction with 3-bromoprop-1-yne. Catalyzed coupling of the resulting 3-(2,5-dimethoxyphenyl)prop-1-ynes 3 under Hay conditions gave the hexa-2,4-diynes 4a-c in good yields. The molecular structures of the diynes 4a and 4b were determined by X-ray diffraction analysis. In each crystal structure, an unusual 1,6-synperiplanar conformation of the hexa-2,4-diyne unit is observed, with the 1,6-diphenyl substituents arranged in a coplanar orientation. According to the crystal structure data obtained, irradiation of diynes 4a and 4b afforded the deeply-colored, highly-ordered polymers 5a and 5b under topochemical control. Oxidation of 4a and 4b with cerium(IV) ammonium nitrate gave the corresponding 1,6-bis(2,5-dimethoxyphenyl)hexa-2,4-diyne-1,6-diones 6a and 6b.
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    Synthesis of Acyclic Carba-Nucleoside Phosphonates, Structural Analogues to Natural Deoxyribonucleotides (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 931-936 
    Details
    ISSN: 1434-193X
    Keywords: Nucleosides ; Phosphonates ; Nucleophilic additions ; C-C coupling ; Reduction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Acyclic carba-nucleoside phosphonates, modelled on natural deoxyribonucleotides have been prepared starting from DNA nucleobases and tert-butyl acrylate. The products obtained from a Michael-type reaction were elongated to β-oxo esters that were first reduced to β-hydroxy esters and then transformed into protected β-hydroxy aldehydes. Wittig-Horner-Emmons reaction with the anion of tetraisopropyl methylenebisphosphonate gave, after deprotection, the desired 4-hydroxy-6-purinyl- or -6-pyrimidinyl-1-hexenylphosphonic acids. A dimer, potential precursor of acyclic polynucleotides (APN), homomorphous with DNA, was also prepared.
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    Electrochemically Induced N-Alkylation of Pyrroles (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 955-958 
    Details
    ISSN: 1434-193X
    Keywords: Tetraethylammonium peroxydicarbonate ; Tetraethylammonium carbonate ; N-alkylated pyrroles ; Electrochemistry ; Electrogenerated bases ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Electrochemically generated tetraethylammonium peroxydicarbonate (TEAPC) and tetraethylammonium carbonate (TEAC) react under very mild conditions with pyrroles affording, after addition of a suitable alkylating agent, the corresponding N-alkylated pyrroles in high yields. C-Alkylated pyrroles have not been isolated in any case reported.
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    Simple Synthesis of (±)-Stigmolone (8-Hydroxy-2,5,8-trimethyl-4-nonanone), the Pheromone of Stigmatella aurantiaca (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 979-980 
    Details
    ISSN: 1434-193X
    Keywords: Ketones ; Myxobacterium ; Pheromones ; Stigmatellaaurantiaca ; Stigmolone ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The racemic myxobacterial pheromone (±)-1 (stigmolone), which induces the formation of the fruiting body of Stigmatellaaurantiaca, was synthesized from methyl isobutyl ketone (2) in 48% overall yield in four steps
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    Photochemical Hydrogen Migration in Methylanthronylidenes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1005-1009 
    Details
    ISSN: 1434-193X
    Keywords: Hydrogen migration ; Anthronylidene ; Quinone methide ; Matrix isolation ; Photochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The photochemistry of 4-methyl-9,10-diazoanthrone (7a) and 1,4-dimethyl-9,10-diazoanthrone (7b) was investigated in argon matrices at 10 K. Visible-light irradiation results in the formation of the anthronylidenes 5a and b, respectively, which were identified by oxygen trapping, by comparison of the IR and UV/Vis spectra with that of the parent anthronylidene 6, and by comparison of the IR spectrum with that calculated by DFT methods. The carbenes 5 are thermally stable under the conditions of matrix isolation; however, irradiation with visible or UV light results in the rearrangement to the quinone methides 10a and b.
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    Metallated 2-Alkenyl Sulfoximines in Asymmetric Synthesis: Regio- and Stereoselective Synthesis of Highly Substituted Oxabicyclic Ethers and Studies Towards the Total Syntheses of the Euglobals G1 and G2 and Arenaran A (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1011-1031 
    Details
    ISSN: 1434-193X
    Keywords: Sulfoximines ; Oxabicyclic ethers ; Asymmetric synthesis ; Euglobal ; Arenaran ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -2-Cyclopentenyl- and 2-cyclohexenylmethyl sulfoximines can be converted into angular carbon-functionalised, highly substituted, isomerically pure (ds ≥ 98%) 2-oxabicyclo[3.3.0]octanes and 2-oxabicyclo[3.4.0]nonanes in high yields by a convenient one-pot sequence. Molecular frameworks such as these can be found in many biologically active natural products. In addition to the methodological work, we report on studies towards the total synthesis of the euglobals G1 and G2 and arenaran A.
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    On the Behavior of 5,8-Bis(trimethylsilyl)cycloocta-1,3,6-triene in Cycloaddition Reactions and Subsequent Chemistry (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1041-1050 
    Details
    ISSN: 1434-193X
    Keywords: Phosphaalkynes ; Cycloadditions ; Polycycles ; Cage compounds ; λ3-Phosphinines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Phosphaalkynes 2 and electron-deficient alkynes 11 readily react in a [4 + 2] cycloaddition process with 5,8-bis(trimethylsilyl)cycloocta-1,3,6-triene (8) in its bicyclic form 10 to furnish regioselectively the tricyclodecadienes 12 and 13, respectively. The phosphorus-containing compounds 12 exhibit structural features which make them suitable for homo-Diels-Alder reactions with electron-deficient acetylenes. A single crystal structure analysis of the homo-Diels-Alder adduct 14b confirmed the structure and relative configuration of the phophatricyclodecadienes 12. In solution the tricyclodecadienes 13 are prone to facile cycloreversion yielding the phthalic esters 15 and the cyclobutene 16. The latter is rapidly converted into the corresponding 1,3-butadiene 18, which can be trapped in a Diels-Alder/phospha-ene/Diels-Alder tandem reaction sequence by phosphaalkyne 2a. The phosphatricyclodecadiene 12 is thermally more stable; loss of cyclobutene 16 only occurs under FVP conditions to afford the λ3-phosphinine 22.
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    Totally Regio- and Stereoselective P-O-to-P-C Rearrangement in the Synthesis of Chiral P-(o-Hydroxyaryl)diazaphospholidine P-Oxides (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1099-1105 
    Details
    ISSN: 1434-193X
    Keywords: Asymmetric synthesis ; Chiral synthons ; P-(o-Hydroxyaryl)diazaphospholidine P-oxides ; Rearrangements ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The totally regio- and stereoselective P-O-to-P-C rearrangement in the synthesis of various chiral P-(o-hydroxyaryl)diazaphospholidine P-oxides has been investigated. This reaction proceeds with excellent yields ranging from 72 to 92%, total retention of configuration at the phosphorus atom, and complete regioselectivity. An exception was found with naphthyl derivatives, which gave mixtures of two regioisomers. In all cases, the products generated have been unambiguously characterized by 1H-, 13C-, and 31P-NMR spectroscopy as well as by X-ray-diffraction analysis.
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    Palladium-Catalyzed Cyclocarbonylation of o-Ethynylphenols and Vinyl Triflates To Form 3-Alkylidene-2-coumaranones (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1137-1141 
    Details
    ISSN: 1434-193X
    Keywords: Cyclocarbonylation ; Alkynes ; Catalysis ; Palladium ; Vinyl triflates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -o-Ethynylphenols react with vinyl triflates, in the presence of tetrakis(triphenylphosphane)palladium(0) and under carbon monoxide, to form 3-alkylidene-2-coumaranones in good yield.
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    S-Linked Thiomimetics of Phytoalexin-Elicitor-Active, Branched Oligosaccharides, Their Synthesis, Protein-Binding Ability and Phytoalexin-Inducing Activity (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1143-1152 
    Details
    ISSN: 1434-193X
    Keywords: Sulfur-linked thiooligosaccharides ; Oligosaccharin thio analogs ; Phytoalexin elicitor thio analogs ; Soybean glucan-binding assays ; Structure-activity relationships ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The sulfur-linked pentathiohexasaccharide 3I,3IV-di-β-D-glucopyranosylthiogentiotetraose (12) has been prepared by a convergent approach involving the reaction of 1,2,4-tri-O-acetyl-6-deoxy-6-iodo-3-S-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-3-thio-β-D-glucopyranose (10) with the sodium salt of 2,3,4-tri-O-acetyl-6-S-[2,4-di-O-acetyl-3,6-di-S-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-3,6-dithio-β-D-glucopyranosyl]-1,6-dithio-β-D-glucopyranose (4). A further reaction, involving the sodium salt of the peracetylated β-1-thio derivative of 12 with 1,2,3,4-tetra-O-acetyl-6-deoxy-6-iodo-β-D-glucopyranose (26), afforded the homologous sulfur-linked hexathioheptasaccharide 3II,3V-di-β-D-glucopyranosylthiogentiopentaose (28). Related sulfur-linked positional isomers 3II,3IV-di-D-β-glucopyranosylthiogentiotetraose (34) and 3III,3V-di-β-D-glucopyranosylthiogentiopentaose (39) have been prepared using analogous synthetic strategies. Thus, SN2 displacement of the iodine atom in 10 by the sodium salt of 2,4-di-O-acetyl-3,6-di-S-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-1,3,6-trithio-β-D-glucopyranose afforded a tetrathiopentasaccharide, which resulted in the pentathiohexasaccharide 34 by a sequence of reactions involving the 1-thioglycose 32 in reaction with 26. The hexathioheptasaccharide 39 was obtained conveniently by the reaction of 26 with the acetylated 1-thio-6I, 3II, 6II, 3IV, 6IV-pentathio derivative 37, followed by deacylation. The four isomeric pentathiohexa- and hexathioheptasaccharides 12,34 and 28,39, respectively, were all found to be active in eliciting phytoalexin accumulation in soybean cotyledon tissue and in binding to a glucan-binding protein of soybean, although to a lesser extent than the corresponding O-oligosaccharides, the alternate thiohexa- and thioheptasaccharides 12,28 being more active as compared to the geminally branched isomers 34,39.
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    Flash Vacuum Thermolysis of Acenaphtho[1,2-a]acenaphthylene, Fluoranthene, Benzo[k]- and Benzo[j]fluoranthene - Homolytic Scission of Carbon-Carbon Single Bonds of Internally Fused Cyclopenta Moieties at T ≥ 1100 °C (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1191-1200 
    Details
    ISSN: 1434-193X
    Keywords: Pyrolysis ; Ring contraction-ring expansion ; Rearrangements ; Homolytic scission ; IGLOIII//6-31G ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Flash vacuum thermolysis (FVT, 1000 °C ≥ T ≥ 1200 °C) of acenaphtho[1,2-a]acenaphthylene (3, C22H12) gave the C22H12 cyclopenta-fused polycyclic aromatic hydrocarbon (CP-PAH) acenaphtho[1,2-e]acenaphthylene (4), cyclopenta[cd]perylene (5) and cyclopenta[def]benzo[hi]chrysene (6). Whereas the formation of 4 is explained by a ring contraction/ring expansion rearrangement of 3, the identification of 5 and 6 suggests that 3 also undergoes homolytic scission of a five-membered ring's Carbon-Carbon single bond furnishing the transient diradical intermediate 7. Ring closure of 7to form 8 after rotation around the Carbon-Carbon single bond of the intact five-membered ring followed by hydrogen shifts will give 6. The latter can rearrange subsequently into 5by ring contraction/ring expansion. The structural assignment of 4 and 5 was supported by independent FVT of 6,12-bis(1-chloroethenyl)chrysene (14) and 3-(1-chloroethenyl)perylene (23), respectively. FVT of 14 (900-1200 °C) gave in a consecutive process 6,12-bis(ethynyl)chrysene (15), 9-ethynylbenz[j]acephenanthrylene (16) and bis(cyclopenta[hi,qr])chrysene (17). Although at T ≥ 900 °C 17 selectively rearranges into 4 by ring contraction/ring expansion, at 1200 °C the latter is converted into 5 presumably via a diradical intermediate obtained by homolytic scission of a single Carbon-Carbon bond of a five-membered ring. FVT of 23 gave in situ 3-ethynylperylene (25), which at 1000 °C is nearly quantitatively converted into 5. The propensity of internal cyclopenta moieties to undergo homolytic scission of a five-membered ring′s Carbon-Carbon single bond was corroborated by independent FVT of benzo[k]- (11) and benzo[j]fluoranthene (12). Previously unknown thermal pathways to important (CP)-PAH combustion effluents are disclosed at T ≥ 1000 °C.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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