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  • Chemistry  (19)
  • Inorganic Chemistry  (3)
  • Azido bridge  (1)
  • Wiley-Blackwell  (19)
  • 1995-1999  (19)
  • 1
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two cis-fused cyclopenteno-1,2,4-trioxanes, 1a and 1b, were subjected to Zn in AcOH or FeCl2 · 4H2O in MeCN. In the first case, the main course was deoxygenation to give cyclopentanone (18) and the 1,4-diphenyl- or 1,4-bis(4-fluorophenyl)cyclopent-3-ene-1,2-diol 10 (Scheme 5). In the second case, isomerization chiefly occurred resulting in the formation of a dimer 9 of the respective 3,5-diaryl-5-hydroxycyclopent-2-enyl 5-hydroxypentanoates 8 (Scheme 3).
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  • 2
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The treatment of artemisinin (1) and β-artemether (6) with Zn dissolving in AcOH for a few hours results in mono-deoxygenation giving deoxyartemisinin (5) and deoxy-β-artemether (7), respectively, as the sole product. In contrast, submission of 1 to FeCl2 · 4 H2O in MeCN at room temperature for 15 min causes only isomerization, (3aS,4R,6aS,7R,10S,10aR)-octahydro-4,7-dimethyl-8-oxo-2H-10H-furo[3,2-i] benzopyran-10-yl acetate (8) and (3R)-3-hydroxydeoxyartemisinin (9) being produced in 78 and 17% yield, respectively. The action of FeCl2 · 4 H2O in MeCN on 6 is similar. Under the same conditions, 6 gives products analogous to 8 and 9 accompanied by an epimeric mixture of 2-[4-methyl-2-oxo-3-(3-oxobutyl)cyclohexyl]propanaldehyde in yields of 32, 23, and 16%, respectively. No epoxide is formed on repeating the last two experiments in the presence of cyclohexene. The deoxygenation of 1 and 6 by Zn is rationalized in terms of its oxophilic nature. The catalyzed isomerization of 1 and 6 by Fe2+ is attributed to the redox properties of the Fe2+/Fe3+ system.
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  • 3
    ISSN: 0009-2940
    Keywords: Gold complexes ; Silver complexes ; Palladium complexes ; S-Donor ; Thiones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: AgClO4 reacts with bidentate ligands 2-(methylthio)pyridine (SMepy) or complexes PPN[Au(Spy)2] [PPN = N(PPh3)2, HSpy = pyridine-2(1H)-thione) or PPN[Au(Sbz)2] (HSbz = benzoxazole-2(3H)-thione), themselves acting as ligands, to give dinuclear complexes [Ag2(μ-SMepy)2](ClO4)2 (1), [AgAu(μ-Spy)2] (2), or [AgAu(μ-Sbz)2] (3), respectively. By treating 1 with [AuCl(tht)] (tht = tetrahydrothiophene), [Au(SMepy)(tht)]ClO4 (4) is obtained which, in turn, reacts with SMepy to give [Au(SMepy)2]ClO4 (5). Similarly, [PdCl2(NCPh)2] reacts with SMepy in 1:1 molar ratio to give [Pd2Cl2(μ-Cl)2(SMepy)2] (6) which reacts with SMepy in 1:2 molar ratio to give [PdCl2(SMepy)2] (7). On the other hand, HSpy reacts with Ag2CO3 to give [Ag2(μ-Spy)2] (8), and (SMepyH)ClO4 reacts with [Au(acac)PPh3] (acacH = acetyl-acetone) to give [Au(SMepy)PPh3]ClO4 (9).
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  • 4
    ISSN: 0009-2940
    Keywords: Gold ; Mercury ; Nitroaryl ; Transmetallation ; Biaryl ; C-C Coupling ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4-Butoxynitrobenzene reacts with [Hg(O2CCF3)2] and LiCl to give [Hg(R)Cl] [R = C6H3NO2-3, OnBu-6 (1)] which is symmetrized by Me4NCl to give [HgR2] (2), the crystal structure of which has been determined. The reaction of 2 with Me4N[AuCl4] affords Me4N[Au(R)Cl3] (3) by a facile transmetallation process. Complex 3 reacts with PPh3 (1:1) to give cis-[Au(R)(PPh3)Cl2] (4). The diaryl complex [-Ph-2)(R)Cl] (5) is obtained by reaction of 3 with [Hg-(C6H4N=NPh-2)2] through a second transmetallation reaction. Complex 5 and PPh3 (1:1) give [AuClPPh3] and the C-C coupling biphenyl RC6H4N=NPh-2 (6).
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  • 5
    ISSN: 0009-2940
    Keywords: Synthesis aryl complexes of gold(III) ; Mercury(II) as transmetallating agent ; X-ray crystal structure ; Ketonylgold(III) complex ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formylarylmercury(II) complex [Hg{C6H(CHO)-6-(OMe)3-2,3,4}2] reacts with 4-butylaniline (1:2) to give [Hg{C6H(CH=NC6H4C4H9-4′)-6-(OMe) 3-2,3,4}2] (1) by a condensation reaction. This complex reacts with Me4-N[AuCl4] (1:1) to give [Hg{C6H(CH=NC6H4C4H9-4′)-6-(OMe) 3-2,3,4}Cl] (2) and the monoarylgold(III) compound cis-C6H4-nBu-4′)-6-(OMe)3-2,3,4}Cl2] (3). This complex reacts with PPh3 (1:1) to give the adduct cis-[Au{C6H(CH=NC6H4-n, Bu-4′)-6-(OMe)3-2,3,4}Cl2(PPh3)] (4) and with AgClO4 (1:1) in acetone to give the ketonyl complex cis-[C6H4-nBu-4′)-6- (OMe)3-2,3,4}-{CH2C(O)Me}Cl] (5). cis-Me4N[Au(C6H4NO2-2)2Cl 2] react with [Hg{C6H3(N=NC6H4OMe-4′)-2-(OMe)-5}Cl] and Me4NCl (1:1:1) to give cis-[C6H4OMe-4′)-2- (OMe)-5}(C6H4NO2-2)2] (6): Similarly, cis-Me4N-[Au(C6H4CF3-2)2 Cl2] (7), obtained by treating [Hg(C6H4CF3-2)2] with Me4N[AuCl4] and Me4NCl (1:1:1), reacts with [Hg(C6H4CH2NMe2-2)Cl] and Me4NCl (1:1:1) to give the triarylgold(III) complex cis-[Me2-2)(C6H4CF3-2)2] (8). This complex can also be obtained by treating cis-[Me2-2)Cl2] with [Hg(C6H4CF3-2)2] and Me4NCl (1:1:1). The crystal structure of 3 reveals the presence of two independent molecules, in one of which the butylphenyl group is disordered. The geometry at the gold atom is square planar; distortions may be attributed to the narrow bite angle and steric repulsion between a chloride ligand and the ortho-methoxy group. The greater trans influence of the aryl ligand causes a great difference in Au-Cl bond lengths.
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  • 6
    ISSN: 0947-3440
    Keywords: Sesquiterpene lactones ; Germacranolides, acid-catalyzed cyclization of, influence of conformation in ; Eudesmanolides ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acid-catalyzed cyclization of the natural germacranolide gallicin (8) yielded, among other products, the 1,4-epoxyeudes-manolide 9, which has a trans-fused decaline system. Under the same conditions the closely related germacranolide shonachalin A (8α-hydroxygallicin) (3) cyclized to the eudesmanolide 4 with a cis fused decaline system. The structures of these cyclization products were secured by means of chemical correlations and X-ray diffraction analyses.
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  • 7
    ISSN: 1434-1948
    Keywords: Gold(I) ; Silver(I) ; S-donor and N-donor ligand ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ligand properties of 2-(phenacylthio)pyridine towards gold(I) and silver(I) have been investigated. From the reactions of the ligand with acetone solutions of [M(PPh3)(acetone)]ClO4 (M = Ag, Au) under various experimental conditions, complexes [(AuPPh3)n{py{SCH2C(O)Ph}-2}](ClO)n, and [(AgPPh3)n(OClO3)n{py{SCH2C(O)Ph}-2}](n = 1-3) have been obtained. The crystal structures of the complexes [(AuPPh3){py{SCH2C(O)Ph}-2}]ClO4 and [(AgPPh3)(OClO3){py{SCH2C(O)Ph}-2}] have been determined by X-ray diffraction. In the cationic gold complex the metal is linearly coordinated to nitrogen and phosphorus, whereas the corresponding silver complex displays a trigonal planar geometry with pyridine, phosphane and perchlorato ligands.
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  • 8
    ISSN: 1434-1948
    Keywords: Bridging ligands ; Manganese ; Azido bridge ; Alternating chain ; Magnetic properties ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ligands 3-ethyl-4-methylpyridine (3-Et,4-Mepy) and azide coordinate to MnII forming an alternating chain with the formula [Mn(3-Et,4-Mepy)2(μ-N3)2]n. This compound crystallizes in the space group P-1. The compound consists of chains of octahedrally coordinated manganese atoms alternately bridged by double end-to-end (μ1,3) and double end-on (μ1,1) azido bridges, which results in a structurally and magnetically alternating chain. The 3-ethyl-4-methylpyridine ligands are arranged trans, completing the six-fold coordination spheres of the manganese atoms. The Mn-Mn distances are distinctly different: Mn(1)-Mn(1A) = 5.149(3) Å (double end-to-end azido bridge) and Mn(1)-Mn(1B) = 3.402(2) Å (double end-on azido bridge). The magnetic properties of the compound, as studied in the temperature range 300-4 K, show bulk antiferromagnetic interaction. Fitting of the magnetic data by using an equation for alternating ferro-antiferromagnetic S = 5/2 1-D systems gives the parameters JAF = -13.7(1) cm-1, JF = 2.4(1) cm-1, g = 2.036(2).
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 673-678 
    ISSN: 0006-3592
    Keywords: image analysis ; Saccharomyces cerevisiae floc ; floc counting ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A standardized image analysis method has been developed permitting determination of the number of yeast flocs and their size distribution. The method includes image grabbing, image enhancement, automatic determination of the appropriate threshold, curve fitting of the areahistogram, determination of the mean single floc area and its standard deviation, and floc counting. The extension of the method to other applications is immediate and straightforward. Two Saccharomyces cerevisiae floc Populations (with ages of 48 and 72 h) were analyzed. The results showed a variation around the mean of 9%-12% for the single floc mean area, 6%-7% for the number of single flocs, and 5%-6% for the total number of flocs. Aggregates of two flocs (doublets) and three flocs (triplets) were enumerated. The correctness of the method was checked by analyzing the parameters of interest as a function of the threshold. The constant correlation between the parameters and the threshold showed the validity and consistency of the method. © 1996 John Wiley & Sons, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 163-170 
    ISSN: 0006-3592
    Keywords: enzymes ; organic solvents ; alcohol inhibition ; activity coefficients ; substrate specificity ; rate-limiting step ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alcohol inhibition of the lipase B from Candida antarctica has been studied through two different approaches: using the same inhibitor (1-butanol) in different organic solvents and using different inhibitors (differing in chain length) in the same solvent. The competitive inhibition constant values obtained in each case correlate with the calculated activity coefficients of the substrate, suggesting that desolvation of the alcohol is the major force changed. Data dispersion observed using the second approach has been interpreted to come from contributions of enzyme-inhibitor interactions to the binding energy. On the other hand, deacylation has been found to be much less influenced by the solvent variation than the acylation step, despite of the fact that solvation of the substrate involved in this step (the alcohol) is expected to change more than for the ester. Concerning the specificity behavior of the enzyme, a bimodal pattern was observed for the deacylation rate dependence on the alcohol chain length, with the highest values for hexanol (C6) and decanol (C10). With regard to the ester specificity, ethyl caproate (C6) is the preferred one. These results have been confronted with those reported for the lipase from Candida rugosa. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 163-170, 1998.
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