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  • 1
    ISSN: 1572-8773
    Keywords: siderophore analog ; amino acid ; dipeptide ; triscatecholate ; synthesis ; Gram-negative bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract New analogs of bacterial siderophores with one, two or three catecholate moieties were synthesized using various mono- and diamino acid and dipetide scaffolds, respectively. In addition to 2,3-dihydroxybenzoyl siderophore analogs and their acylated derivatives, 3,4-dihydroxybenzoyl derivatives were prepared. Furthermore, the synthesis of a new triscatecholate serving as an intimate model for enterobactin is reported. Most of the new compounds gave a positive CAS-test and were active as siderophores tested by growth promotion assays with a set of siderophore indicator mutants under iron limitation. Structure-activity-correlations have also been studied.
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  • 2
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    Journal of thermal analysis and calorimetry 60 (2000), S. 123-130 
    ISSN: 1572-8943
    Keywords: DTA ; IR spectra ; 3-methylglutarates ; synthesis ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Conditions for the formation of rare earth element (Y, La–Lu) 3-methylglutarates were studied and their quantitative composition and solubilities in water at 293 K were determined (10–2 mol dm–3). The IR spectra of the prepared complexes with general formula Ln2(C6H8O4)3 nH2O (n=3–8) were recorded and their thermal decomposition in the air were investigated. During heating the hydrated 3-methylglutarates are dehydrated in one step and next anhydrous complexes decompose to oxides Ln2O3 with intermediate formation Ln2O2CO3 (Y, La, Nd–Gd) or directly to the oxides, Ln2O3, CeO2, Pr6O11 and Tb4O7 (Ce, Pr, Tb–Lu).
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  • 3
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    Journal of thermal analysis and calorimetry 61 (2000), S. 127-134 
    ISSN: 1572-8943
    Keywords: synthesis ; thermodynamic parameters ; TG/DTA ; tribenzyl tin(IV) complexes with thiohydrazides and thiodiamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Tribenzyl tin(IV) chloride complexes of morpholine N-thiohydrazide (L1), aniline-N-thiohydrazide (L2),N-(morpholine-N-thio)-1,3-propanediamine (L3) and (aniline-N-thio)-1,3-propanediamine (L4) of the type (C6H5CH2)3Sn(L)Cl (where L=L1, L2, L3 and L4) have been synthesised in dioxane and in H2O and acetone mixture. These were characterized by C,H,N-analysis, UV, IR and 1HNMR spectral studies. In both the complexes ligands act as bidentate, coordinating through sulphur and terminal nitrogen. The complexes are 1:1 metal ligand complexes. Various thermodynamic parameters have been calculated for the decomposition steps using TG/DTA curves in air as well as nitrogen atmosphere.
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  • 4
    ISSN: 1572-9001
    Keywords: Piperazines ; coumarins ; synthesis ; X-ray crystallography ; semiempirical methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The new piperazine derivative (1) was synthesized by linking a coumarin system to a heteroarylpiperazine via a propyloxy chain. Its molecular structure, as determined by X-ray diffractometry is compared to those computed by three semiempirical methods. PM3 and MNDO give the best accuracy in reproducing the bond distances and angles, respectively. AM1 gives the best agreement with X-ray in reproducing the whole three-dimensional (3D) structure of this molecule. An analysis of these results at the light of other similar previously reported is carried out.
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  • 5
    ISSN: 1573-9171
    Keywords: dimethyl 2-benzoyl-2-ethyl-3-phenylcyclopropane-1,1-dicarboxylate ; alfa,alfa-dibromobutyrophenone ; zinc ; dimethyl benzylidenemalonate ; synthesis ; X-ray diffraction analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reaction of alfa,alfa-dibromobutyrophenone with dimethyl benzylidenemalonate in the presence of zinc gives dimethyl 2-benzoyl-2-ethyl-3-phenylcyclopropane-1,1-dicarboxylate as a single geometrical isomer. Its structure was determined by X-ray diffraction analysis.
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  • 6
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    Glycoconjugate journal 17 (2000), S. 795-805 
    ISSN: 1573-4986
    Keywords: chondroitin sulphate ; glycosaminoglycans ; heparin ; hyaluronan ; lymph node ; proteoglycans ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Previous studies of hyaluronan uptake and catabolism by lymph nodes indicated that the nodes might also add some HA of low molecular weight to the unabsorbed fraction that passes through from afferent to efferent lymph vessels. The ability of lymph nodes to synthesise HA and proteoglycans was therefore examined (i) by perfusion of [3H] acetate through an afferent lymph vessel in vivo, and recovery of labeled products from the efferent lymph vessel and from the node after perfusion; and (ii) by tissue culture of lymph nodes with [3H] acetate. Perfusion of lymph nodes with [3H] acetate in situ yielded: (a), in outflowing lymph, small amounts of chondroitin/dermatan sulfate within the first hour which continued to be produced for up to 24[emsp4 ]h; heparin in the second hour and HA in the third. In the nodes removed 17 to 19[emsp4 ]h later, equal amounts of hyaluronan and chondroitin/dermatan sulfate and heparan sulfate proteoglycans were detected. In the tissue culture of lymph nodes: (1) HA, heparin and proteoglycans of heparan sulfate and chondroitin/dermatan sulfate were released into the medium but in the cell extract only heparan sulfate proteoglycan was detected; and (ii) molecular weight of the released hyaluronan ranged widely but was mostly less than 4–5×105[emsp4 ]D; heparan sulfate proteoglycan was 2.8×104 to 9.4×105[emsp4 ]D; heparin 7.9×104[emsp4 ]D and chondroitin sulfate 1.3×104[emsp4 ]D, suggesting that the chondrotin sulfate were released from their proteoglycans core by enzymic degradation. It is concluded that lymph nodes can release HA, heparin, heparan sulfate and chondroitin/dermatan sulfate proteoglycans into efferent lymph but the amount of hyaluronan is likely to be small without immune or other stimulation and its molecular weight is lower than in other tissues.
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  • 7
    ISSN: 1573-4986
    Keywords: N-glycan ; synthesis ; unnatural glycosidic linkage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract As part of a program to explore the structural requirement of N-glycans in the carbohydrate-mediated biological interactions, N-linked pentasaccharide core structure was stereochemically modified in terms of glycosidic linkage. Three isomers, α-D-Man-(1→3)-[α-D-Man-(1→6)]-α-D-Man-(1→4)-β-D-GlcNAc-(1→4)-β-D-GlcNAc-L-Asn, α-D-Man-(1→3)-[α-D-Man-(1→6)]-β-D-Man-(1→4)-α-D-GlcNAc-(1→4)-β-D-GlcNAc-L-Asn, and α-D-Man-(1→3)-[α-D-man-(1→6)]-α-D-Man-(1→4)-α-D-GlcNAc-(1→4)-β-D-GlcNAc-L-Asn, were synthesized. Synthesis of the pentasaccharide with natural linkage is also described.
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  • 8
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    Chemistry of natural compounds 36 (2000), S. 302-307 
    ISSN: 1573-8388
    Keywords: synthesis ; β-sitosterol ; 2β ; 3β ; 14α-trihydroxy-Δ4,7-6-ketosteroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A scheme using β-sitosterol as an example for synthesizing 2β, 3β, 14α-trihydroxy-Δ4,7-6-ketosteroids and their derivatives from 3β-hydroxy-Δ5-steroids was developed.
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  • 9
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    Chemistry of natural compounds 36 (2000), S. 377-380 
    ISSN: 1573-8388
    Keywords: synthesis ; stigmasterol ; ecdysteroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new synthesis of ecdysteroids from stigmasterol has been developed.
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  • 10
    ISSN: 1573-8388
    Keywords: 5-phenyl-7H-furo[2,3-g]chromen-7-one ; 9-phenyl-7H-furo-[2,3-f]chromen-7-one ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 5-Phenyl-7H-furo[2,3-g]chromen-7-ones and 9-phenyl-7H-furo-[2,3-f]chromen-7-ones, new analogs of psoralen and allopsoralen, are synthesized from 7-hydroxy- and 5-hydroxy-4-phenylcoumarins
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  • 11
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    Chemistry of natural compounds 36 (2000), S. 485-492 
    ISSN: 1573-8388
    Keywords: 5-hydroxy- and 7-hydroxy-4-phenylcoumarins ; 8-dialkylaminomethyl-4-phenylcoumarins ; 6-dialkylaminomethyl-4-phenylcoumarins ; 8-aminoacylmethyl-7-hydroxy-4-phenylcoumarins ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Aminomethylation of 5-hydroxy- and 7-hydroxy-4-phenylcoumarins by substituted 1,1-diaminomethanes is studied. Mannich condensation of amino acids and their esters with 7-hydroxy-4-phenylcoumarin gives a series of 8-aminoacylmethylcoumarins and 4-phenyl-9,10-dihydro-2H,8H-chromeno[8,7-e][1,3]oxazin-2-ones
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  • 12
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    Chemistry of natural compounds 36 (2000), S. 574-578 
    ISSN: 1573-8388
    Keywords: thiozole derivatives ; 7,8-dihydroxychromones ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Modified analogs of isoflavolignans are prepared by annelation of dioxole, dioxane, and dioxepan fragments to 3-thiazolyl-7,8-dihydroxychromones
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  • 13
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    Chemistry of natural compounds 36 (2000), S. 345-348 
    ISSN: 1573-8388
    Keywords: synthesis ; saccharose esters ; aromatic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Di- and triesters of saccharose with aromatic acids are synthesized by transesterification of the methyl esters of the corresponding acids with saccharose. The structures of the resulting compounds are confirmed by IR spectroscopy, PMR, and 13 C NMR.
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  • 14
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    Chemistry of natural compounds 36 (2000), S. 510-512 
    ISSN: 1573-8388
    Keywords: synthesis ; stigmasterol ; (22S,23S,24S)-3β,14α,22,23-tetrahydroxy-5α-stigmast-7-en-6-one
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A tetrahydroxyketone that is a structural analog of ecdysteroids is synthesized from stigmasterol
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  • 15
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    Chemistry of heterocyclic compounds 36 (2000), S. 1007-1025 
    ISSN: 1573-8353
    Keywords: synthesis ; structure ; properties ; 1,5-diketones ; pentane-1,5-diones ; 2-pentene-1,5-diones ; 1,3,5-triaryl-2,4-dichloro-2-pentene-1,5-diones ; arylidenedicyclanones ; heterylidenedicyclanones ; 2-(3-oxo-1,3-diphenylpropyl)tetralones ; 4-(1,3-diaryl-3-oxopropyl)pyrazolones ; pyrans ; dihydropyrans ; tetrahydropyrans ; sym-octahydroxanthenes ; pyrylium salts ; aroylfurans ; 2-aroyl-4-chlorofurans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Literature and characteristic experimental data correlated in the review concern the intramolecular cyclization by various means of substituted 1,5-diketones of the acyclic, semi-, and bicyclic series, proceeding to the formation of oxygen-containing heterocycles, such as pyrans, pyrylium salts, di- and tetrahydrofurans, and their condensed analogs, aroylfurans etc.
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  • 16
    ISSN: 1573-1561
    Keywords: Methyl 2,6,10-trimethyltridecanoate ; methyl 2,6,10-trimethyldodecanoate ; Euschistus heros ; Piezodorus guildinii ; pheromone ; synthesis ; Heteroptera ; Pentatomidae ; biological activity ; stink bugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Methyl 2,6,10-trimethyltridecanoate (1) and methyl 2,6,10-trimethyldodecanoate (2) have been identified as male-produced sex pheromones of the Brazilian soybean stink bugs Euschistus heros (F.) and Piezodorus guildinii (Westwood). In order to establish a defined attractive blend for both species, compounds 1 and 2 were synthesized as mixtures of stereoisomers to be employed in behavior bioassays. (±)-Citronellol (3) was utilized as starting material, and the syntheses was carried out in six steps with good overall yield. When tested alone, synthetic compounds 1 and 2 proved to be active in a two-choice olfactometer; however, a 20 : 1 mixture of 1 and 2 was much more attractive to E. heros females. A similar blend had been found among the headspace volatiles of males.
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  • 17
    ISSN: 1573-1111
    Keywords: synthesis ; solvent extraction ; alkali cation ; crown ether ; calixarene ; calixarene biscrown ; complexation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A series of calix[4]arene-bis-crownethers were synthesized in a fixed 1,3-alternateconformation with good yields by the reaction of amonocyclic calixcrown ether with multi-ethyleneglycoldi-p-toluenesulfonate in the presence of cesiumcarbonate. In the preparation of the monocycliccalixcrown ethers (1 and 2), the use ofpotassium carbonate as a base provided the best yieldregardless of the template concept. In two phaseextraction and competitive transport experiments forligand-metal complexation, calix[4]arene biscrown(5) provided the best selectivity for potassiumion. When a calixbiscrown ether (4) bearingdifferent sized crown ether loops coordinates to K+and Cs+, respectively, the changes of peak splittingpatterns and chemical shift on 1H NMR spectra aredependent on the complexed metal ion species.
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  • 18
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    Journal of inclusion phenomena and macrocyclic chemistry 37 (2000), S. 103-120 
    ISSN: 1573-1111
    Keywords: FER type zeolite ; synthesis ; ion exchange ; structural characterization ; sorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Synthesis of K, Na -FER type zeolite wasstudied in the reactant system ofK 2O-–Na 2O-–Al 2O 3-–SiO 2-–CO 3-–HCO 3-ndash;H 2O.Sodium silicate, silica sol andfumed silica were tested as the silica source, andsolid aluminum sulfate, aluminum hydroxide andmeta-kaolinite as the alumina source. The startingmaterials, the composition of the reactant, and thesynthesis temperature greatly influence the phasescrystallized. A pure phase of K, Na-FER zeolite washydrothermally prepared at 208 °C with sodiumsilicate and solid aluminum sulfate as startingmaterials. The optimum composition of the reactantfor synthesis of the pure FER zeolite was determined. Chemical analysis, XRD, FT-IR, 29Si and 27AlMAS NMR, TG/DTA, and adsorption of nitrogen, methanoland n-hexane were used to characterize the zeolite andcompared with the reference sample of perfect singlecrystals of siliceous FER zeolite. The content ofK+and Na+in the zeolite decreases graduallywith the times of the treatment ofion-exchange/calcination, leading to an increase in theadsorption capacities of nitrogen and methanol, anda decrease of the loading of n-hexane. The location ofthe K+, the stacking faults, and dealumination of thezeolite framework are discussed based on the ion exchange and adsorption behavior.
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  • 19
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    Journal of thermal analysis and calorimetry 61 (2000), S. 909-914 
    ISSN: 1572-8943
    Keywords: cadmium(II) ; complexes ; mercury(II) ; o-vanillin oxime ; spectral and thermal studies ; synthesis ; zinc(II)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zinc(II), cadmium(II) and mercury(II) complexes of o-vanillin oxime have been synthesized and characterized by different physicochemical techniques. All the complexes have been subjected to non-isothermal decomposition studies in nitrogen atmosphere using thermogravimetry. The kinetic parameters for the decomposition of these complexes were evaluated using different methods and comparatively better results were obtained by these different methods. It has also been found that the decomposition processes of all these complexes follow first order kinetics.
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  • 20
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    Reaction kinetics and catalysis letters 71 (2000), S. 201-207 
    ISSN: 1588-2837
    Keywords: Alumina aerogel ; synthesis ; gelation ; calcination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Synthesis of alumina aerogels was carried out by hydrolysis of aluminium isopropanolate and butanolate in benzene, methanol and isopropanol solutions as components of support precursors followed by gelation, drying under supercritical conditions and calcination. The influence of the type of precursor and solvent, synthesis temperature as well as drying and calcination temperature on bulk density, specific surface area and total pore volume was investigated.
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  • 21
    ISSN: 1573-1561
    Keywords: Chemical defense ; sponges ; predation ; Agelas ; pyrrole–imidazole alkaloids ; structure–activity relationship ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We investigated the relationship between the structures of pyrrole-containing alkaloids from marine sponges of the genus Agelas and their capacity to deter feeding by the omnivorous Caribbean reef fish, Thalassoma bifasciatum. Seven natural products were assayed at volumetric concentrations of 1, 5, and 10 mg/ml: dispacamide A, keramadine, oroidin, midpacamide, 4,5-dibromopyrrole-2-carboxylic acid, 4,5-dibromopyrrole-2carboxamide, and racemic longamide A. We also assayed 14 structural analogs obtained mostly by chemical synthesis. Of the seven natural products, only rac-longamide A was not significantly deterrent at any of the assay concentrations. The pyrrole moiety was required for feeding inhibition activity, while the addition of the imidazole group enhanced this activity. Variously functionalized imidazoles lacking the pyrrole moiety were not deterrent. Combinations of the natural products appeared to have an additive effect on feeding inhibition; there was no evidence of synergy. Given their high concentrations in sponge tissue, dispacamide A and oroidin most probably serve as the primary chemical defenses of many Agelas sp., while minor compounds such as keramadine are not present in high enough concentrations to contribute much to chemical defense.
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  • 22
    ISSN: 1573-1561
    Keywords: Spodoptera exigua Hübner ; Zea mays L. ; elicitors ; isolation ; identification ; synthesis ; volicitin ; 17-hydroxylinolenic acid ; 17-hydroxylinoleic acid ; linolenic acid ; linoleic acid ; glutamine conjugates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Oral secretion of beet armyworm caterpillars (BAW), when applied to damaged tissues of corn seedlings, induces the seedlings to emit volatile compounds that attract the natural enemies of the caterpillars. The key elicitor present in BAW oral secretions is N-[17-hydroxylinolenoyl]-L-glutamine (volicitin). Analysis of the oral secretion showed that it also contained N-[17-hydroxyolinoleoyl]-L-glutamine, free 17-hydroxylinolenic, and 17-hydroxylinoleic acid, the glutamine conjugates of linolenic and linoleic acid as well as free linolenic and linoleic acid. Here we present the identification and synthesis of the hydroxy acids and of glutamine conjugates.
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  • 23
    ISSN: 1573-3904
    Keywords: antibodies ; chicken galanin ; segments ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We describe the synthesis of the first aviangalanin (GAL), chicken GAL, and its N-terminal and C-terminal segments by solid-phasesynthesis, using Boc/Bzl amino acidprotection groups and MBHA resin. The three peptides were prepared with purities of over97%, as determined by RP-HPLC, HPCE, FAB-MS or ESI-MSand amino acid analysis.Antibodies against these synthetic peptides wereraised in rabbits and used forimmunohistochemical localization of GAL-immunoreactiveneurons in chicken brain.
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  • 24
    ISSN: 1573-3904
    Keywords: antibodies ; chicken galanin ; segments ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary We describe the synthesis of the first avian galanin (GAL), chicken GAL, and its N-terminal and C-terminal segments by solid-phase synthesis, using Boc/Bzl amino acid protection groups and MBHA resin. The three peptides were prepared with purities of over 97%, as determined by RP-HPLC, HPCE, FAB-MS or ESI-MS and amino acid analysis. Antibodies against these synthetic peptides were raised in rabbits and used for immunohistochemical localization of GAL-immunoreactive neurons in chicken brain.
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  • 25
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    Chemistry of natural compounds 36 (2000), S. 299-301 
    ISSN: 1573-8388
    Keywords: synthesis ; 2,3-di-O-α-L-rhamnopyranoside ; 25(S)-spirost-5-en-2α, 3β-diol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The two hydroxyls of yuccagenin can be glycosylated by Koenigs-Knorr condensation with acetobromorhammose in dichloroethane in the presence of mercuric cyanide. The bisrhamnoside of yuccagenin markedly lowers the cholesterol and triglyceride content in blood serum of healthy animals and animals with experimental hyperlipidemia.
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  • 26
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    Chemistry of natural compounds 36 (2000), S. 342-344 
    ISSN: 1573-8388
    Keywords: synthesis ; D-mannite esters ; aromatic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mono- and diesters of D-mannite with aromatic acids are synthesized. The structures of the resulting compounds are confirmed by IR spectroscopy, PMR, and 13 C NMR.
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  • 27
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    Chemistry of natural compounds 36 (2000), S. 11-39 
    ISSN: 1573-8388
    Keywords: acetogenin pheromones ; synthesis ; literature review
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Syntheses of acetogenin pheromones using acetylene derivatives are reviewed.
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  • 28
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    Chemistry of natural compounds 36 (2000), S. 105-119 
    ISSN: 1573-8388
    Keywords: insect pheromones ; 10-undecenoic acid ; synthesis ; literature review
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The literature on the use of 10-undecenoic acid in the synthesis of insect pheromones is reviewed.
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  • 29
    ISSN: 1573-8388
    Keywords: Artemisia glabella ; artemisia ketone ; 5-(1′,1′-dimethylallyl)-3,3-dimethyl-3H-pyrazole-N,N′-dioxide ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxime of artemisia ketone is smoothly converted to the pyrazole derivative by sodium nitrite and acetic acid in CHCl3. The structure of the pyrazole was found by x-ray structural analysis. The PMR and13C NMR spectra were interpreted using two-dimensional1H−13C NMR (COSY, COLOC).
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  • 30
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    Chemistry of natural compounds 36 (2000), S. 156-158 
    ISSN: 1573-8388
    Keywords: (+)-Driman-8α,11-diol ; sclareol ; (12R)-8α,12-epoxy-14,15-bisnorlabdan-13-one ; (12S)-8α,12-expoxy-12-acetoxy-13,14,15,16-tetranorlabdane ; 8α,12-epoxy-13,14,15,16-tetranorlabd-11-ene ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A four-step synthesis of driman-8α,11-diol from sclareol in 44% total yield is described that includes the intermediates (12R)-8α,12-epoxy-14,15-bisnorlabdan-13-one, (12S)-8α,12-epoxy-12-acetoxy-13,14,15,16-tetranorlabdane and 8α,12-epoxy-13,14,15,16-tetranorlabd-11-ene.
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  • 31
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    Chemistry of natural compounds 36 (2000), S. 189-191 
    ISSN: 1573-8388
    Keywords: β-sitosterol ; (24R,6E)-24-ethylcholest-6-hydroxyimino-4-en-3-one ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract (24R,6E)-24-ethylcholest-6-hydroxyimino-4-en-3-one (1), which was isolated previously fromCinachyrella spp. sponges, is synthesized in five steps from β-sitosterol in 30% overall yield.
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  • 32
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    Chemistry of natural compounds 36 (2000), S. 192-197 
    ISSN: 1573-8388
    Keywords: cytisine ; 1-mono- and 1,3-disubstituted 5-arylmethylbarbituric acids ; 1,3-dimethyl-5-arylmethyl-5-cytisylmethylbarbituric acids ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Reaction of cytisine with 1-mono- and 1,3-disubstituted 5-arylmethylbarbituric acids in the presence of formaldehyde results in aminomethylation of C-5 to form the corresponding 5-cytisylmethylbarbituric acids. The structures of the products are found using PMR spectroscopy and mass spectrometry. 1-Phenyl-5-(2,4-dimethoxybenzyl)-5-cytisylmethylbarbituric acid is obtained as a mixture of two steroisomers in an approximately 2∶1 ratio.
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  • 33
    ISSN: 1573-8388
    Keywords: pheromones ; Synanthedon tipuliformis ; Zenzera pyrina ; 10-undecenoic acid ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new synthesis of octadeca-2E,13Z-dienylacetate from 10-undecenoic acid is developed by constructing the carbon framework of the pheromone in the key step and introducing the 2E double bond by Doebner condensation of hexadec-11-ynal and malonic acid.
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  • 34
    ISSN: 1573-8388
    Keywords: pheromones ; Drosophila mulleri ; Mayetiola destructor ; ethyl-3S-hydroxybutanoate ; 2S-tridecylacetate ; 2S-tridec-10E-enylacetate ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Syntheses are developed for 2S-tridecyl- and 2S-tridec-10E-enylacetates, sex pheromones of the fruit flyDrosophila mulleri and the Hessian flyMayetiola destructor, respectively, that are based on ethyl-3S-hydroxybutanoate, a product from enzymatic reduction of ethyl acetoacetate by the soil yeast strain “80-1”.
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  • 35
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    Catalysis surveys from Japan 3 (1999), S. 119-126 
    ISSN: 1572-8803
    Keywords: organozeolite ; microporous and mesoporous material ; inorganic-organic composite ; synthesis ; phosphonate ; aluminomethylphosphonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Attempts in developing organozeolites, namely microporous and mesoporous crystalline inorganic-organic composites with a zeolite-like three-dimensional framework and organic moieties covalently connected to the framework, are briefly reviewed. MCM-41 type mesoporous materials modified by organic functional groups have been prepared by use of organosiloxane as a part of Si sources and by post-modification of the purely inorganic materials using organosiloxane. Also, the incorporation of organic moieties into the zeolite frameworks has been tried. Recently, several novel metal organophosphonates with a three-dimensional framework, which can be regarded as organozeolites, have been prepared. Along with these new attempts, the authors' studies in preparation, structural analysis and gas adsorption properties of microporous aluminomethylphosphonates are introduced.
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  • 36
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    Journal of inorganic and organometallic polymers and materials 9 (1999), S. 63-77 
    ISSN: 1572-8870
    Keywords: Octamethylcyclo-di(meta-silphenylenesiloxane) ; poly(silphenylene-siloxane) ; synthesis ; X-ray structure ; 4-dimethylaminopyridine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Octamethylcyclo-di(meta-silphenylenesiloxane) 1 (cyclic meta-dimer) was synthesized from 1,3-bis(dimethylhydroxysilyl)benzene 7 in a dilute THF solution, in the presence of a catalytic amount of 4-dimethylaminopyridine (DMAP). In contrast, only small amounts of the cyclic meta-dimer 1, cyclic meta-trimer 2, cyclic meta-tetramer, etc. were obtained when the condensation reaction was carried out with the catalyst n-hexylamine 2-ethylhexoate or sodium hydroxide. The major product in these reactions is polymer 8. The structure of compound 1 was confirmed by X-ray crystallography. This cyclic molecule is most likely unstrained since the X-ray structure reveals that the Si–O–Si bond angle is 142.1(1)° which is similar to that in most unstrained siloxane compounds.
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  • 37
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    Journal of thermal analysis and calorimetry 58 (1999), S. 393-401 
    ISSN: 1572-8943
    Keywords: dinuclear Ni(II) complex ; non-isothermal kinetics ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Crystal of the complex Ni2L (ClO4)2 was obtained by reaction of Ni(ClO4)2 and macrocyclic ligand H2L, where L2− is the dinucleating macrocycle with two 2,6-di(aminomethyl)-4-methyl phenolate entities combined by the same two lateral chains, –(CH2)2–NH–(CH2)2–, at the amino nitrogens. The thermal decomposition processes of the title complex were studied in a dynamic atmosphere of dry argon using TG-DTG. The kinetic analysis of the first and second thermal decomposition steps were performed via the TG-DTG curves, and the kinetic parameters were obtained from analysis of the TG-DTG curves with integral and differential methods. The most probable kinetic function was suggested by comparison of the kinetic parameters.
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  • 38
    ISSN: 1573-4919
    Keywords: apolipoprotein B ; synthesis ; secretion ; clearance ; nonsense ; mutation ; mRNA metabolism ; apoB48
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Low levels of cholesterol are protective against development of coronary artery disease. Heterozygous hypobetalipoproteinemic individuals expressing truncated apolipoprotein (apo)B as a result of mutation in the capob gene have low levels of cholesterol and apoB in their plasma. To study the molecular mechanism of low levels of apoB in these individuals, we employed a previously reported knock out mouse model generated by targeted modification of the apob gene. The heterozygous, apoB-100/B-81, mice express full length and truncated apoB, B-81, and have 20 and 35% lower levels of total cholesterol and apoB, respectively, when compared to WT (apoB-100/B-100) mice. The majority of the truncated apoB, B-81, fractionated in the VLDL- density range. The mechanism of low levels of apoB in B-100/B-81 mice was examined. Total hepatic apoB mRNA levels decreased by 15%, primarily due to lower levels of apoB-81 mRNA. Since apoB mRNA transcription rates were similar in B-100/B-100 and B-100/B-81 mice, low levels of mutant apoB-81 mRNA occurred by enhanced degradation of apoB mRNA transcript containing premature translational stop codon. ApoB synthesis measured on isolated hepatocytes decreased in B-100/B-81 mice by 35%, while apoB-48, apoE, and apoAI syntheses remained unchanged. Metabolic studies using whole animal showed a 32% decrease in triglyceride secretion rates, consistent with the apoB secretion rates. Inhibition of receptor-mediated clearance of apoB-81-containing particles resulted in greater relative accumulation of apoB-81 in plasma than apoB-100, suggesting enhanced clearance of apoB-81-containing particles. These results demonstrate that low levels of apoB in heterozygous hypobetalipoproteinemic mice occurs by low rates of apoB secretion, and increased clearance of truncated apoB. Similar mechanisms appear to contribute to low levels of apoB in hypobetalipoproteinemic humans.
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  • 39
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    Topics in catalysis 9 (1999), S. 13-34 
    ISSN: 1572-9028
    Keywords: boralites ; synthesis ; characterization ; isomorphous substitution ; boron
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The synthesis, physico-chemical characterization and catalytic activity of boron-containing molecular sieves (boralites) are reviewed and discussed. Incorporation of boron in the silica framework of several phases has been assessed by structural and spectroscopic evidence. Compared with the aluminosilicate parent compounds, boralites display weaker acid strength sufficient, however, for catalyzing several reactions.
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  • 40
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    Topics in catalysis 9 (1999), S. 59-76 
    ISSN: 1572-9028
    Keywords: synthesis ; silica zeolites ; framework density ; phase selectivity ; connectivity defects
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Recent advances in the synthesis of all-silica and high-silica crystalline molecular sieves in fluoride media, with special regard to low framework density phases, are presented. The fundamental differences between the synthesis in hydroxide and fluoride media with respect to the properties of the materials obtained and the phase selectivity of the crystallization are discussed.
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  • 41
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    Topics in catalysis 9 (1999), S. 93-103 
    ISSN: 1572-9028
    Keywords: mixed-bonded ; aluminophosphates ; open-framework ; layered ; synthesis ; structure ; hydrothermal ; solvothermal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The structural features, the synthesis and the role of templates in the synthesis for mixed-bonded open-framework aluminophosphates and related layered materials will be reviewed in this article. These aluminophosphate materials differ from the (4,2)-connected aluminophosphates and zeolites in that they contain TO5 and/or TO6 primary building units or terminal T-O bonds (T stands for Al or P). The extra ligands for the TO5 and TO6 units in the aluminophosphates with framework Al/P = 1 are either bridging OH groups or H2O molecules in most cases whereas the terminal T-O bonds are either P-OH or P=O species with P=O bonds being prevalent in layered aluminophosphates. Most of TO5 or TO6 containing aluminophosphates are prepared using a cyclic amine or a diamine as the structure directing agent (template), and the aluminophosphates with Al/P〈1 or the layered materials tend to form from an alcoholic medium. Both synthetic conditions and templates play a critical role in determining the composition and structural feature of these materials.
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  • 42
    ISSN: 1573-1561
    Keywords: Calomyrmex sp. males ; mandibular gland secretion ; 3,5,6-trimethyltetrahydropyran-2-ones ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The relative configuration of a δ-lactone isolated from the mandibular gland extracts of Calomyrmex sp. males has been determined to be (3SR,5RS,6SR)-3,5,6-trimethyltetrahydropyran-2H-one after the synthesis of the four possible racemates and comparison of their mass spectra and gas chromatographic properties with those reported in the literature for the natural product.
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  • 43
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    Journal of sol gel science and technology 15 (1999), S. 201-209 
    ISSN: 1573-4846
    Keywords: sol-gel ; synthesis ; protoenstatite ; 29Si-NMR ; freeze-drying
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Three different magnesium silicate sols were prepared from Mg(OMe)2 and TEOS for which hydrolysis with H2O2 and H2O was under stoichiometric, stoichiometric, or over stoichiometric. Xerogels were prepared from the sols by simple evaporation, spray-drying, or freeze-drying. The freeze-dried precursor formed mostly protoenstatite, a high-temperature polymorph of enstatite (MgSiO3) that is generally not stable at room temperature; the other precursors formed mixtures of protoenstatite and clinoenstatite. The three xerogels and their calcined products were studied with XRD, HTXRD, BET, carbon analysis, TG/DTA and29 Si-NMR. Residual carbon was found to be an important factor in the crystallization, and 29Si-NMR spectroscopy was found to be a better tool than XRD to assess the phase purity of protoenstatite.
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  • 44
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    Glycoconjugate journal 16 (1999), S. 197-203 
    ISSN: 1573-4986
    Keywords: gangliosides ; synthesis ; GM3 ; GD3 ; lactones ; Ganglioside ; glycosphingolipid nomenclature ; LacCer, β-Gal-(1-4)-β-Glc-(1-1)-Cer ; GM3, II3-α-Neu5AcLacCer, α-Neu5Ac-(2-3)-β-Gal-(1-4)-β-Glc-(1-1)-Cer ; GD3, II3(-α-Neu5Ac)3LacCer, α-Neu5Ac-(2-8)-α-Neu5Ac-(2-3)-β-Gal-(1-4)-β-Glc-(1-1)-Cer ; GM2, II3-α-Neu5AcGg3Cer, β-GalNAc-(1-4)-[α-Neu5Ac-(2-3)]-β-Gal-(1-4)-β-Glc-(1-1)-Cer ; Gg4Cer, β-Gal-(1-3)-β-GalNAc-(1-4)-β-Gal-(1-4)-β-Glc-(1-1)-Cer ; GM1, II3-α-Neu5AcGg4Cer, β-Gal-(1-3)-β-GalNAc-(1-4)-[α-Neu5Ac-(2-3)]-β-Gal-(1-4)-β-Glc-(1-1)-Cer ; GM1-lactone, β-Gal-(1,3)-β-GalNAc-(1-4)-[α-Neu5Ac-(2-3,1-2)]-β-Gal-(1-4)-β-Glc-(1-1)-Cer ; GD1b, II3(-α-Neu5Ac)2 Gg4Cer, β-Gal-(1-3)-β-GalNAc-(1-4)-[α-Neu5Ac-(2-8)-α-Neu5Ac-(2-3)]-β-Gal-(1-4)-β-Glc-(1-1)Cer ; GD1b-dilactone, β-Gal-(1-3)-β-GalNAc-(1-4)-[α-Neu5Ac-(2-8, 1-9)-α-Neu5Ac-(2-3, 1-2)]-β-Gal-(1-4)-β-Glc-(1-1)-Cer
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A simple procedure is described for preparing GM3 ganglioside, from a few milligrams to grams, from GM1-lactone (Sonnino et al., (1985) Glycoconjugate J 2: 343–54) [1]. The synthesis was carried out under the following optimal conditions: 30 mM GM1-lactone in 0.25 M H2SO4 in DMSO, 30 min, 70°C, nitrogen atmosphere, strong stirring. The yield of GM3 was 55%. The procedure applied to milligram amounts of GD1b-dilactone gave GD3 ganglioside.
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  • 45
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    Journal of inclusion phenomena and macrocyclic chemistry 33 (1999), S. 459-467 
    ISSN: 1573-1111
    Keywords: cyclodextrin derivatives ; cyclodextrin glycerol ethers ; synthesis ; complexation ; solubilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Epichlorohydrin was reacted with cyclodextrins to form the non-cyclic and cyclic glycerol ethers of β- and γ-cyclodextrin (abbreviated as glyc-CD). Cyclic substitution extends the cyclodextrin cavity in a way that is as rigid and non-polar as the cavity of the parent cyclodextrin. Derivatives with extended cavities should better accommodate large or odd shaped molecules. The binding of drugs to the new cyclodextrin derivatives was investigated, through degradation rate studies and solubilization studies, and compared to that of β-cyclodextrin, γ-cyclodextrin and hydroxypropyl-β-cyclodextrin. The inclusion binding of small molecules such as acetazolamide, ethoxyzolamide and chlorambucil, in the glyc-CDs was either increased or decreased compared to the other cyclodextrins. However, larger molecules, such as indomethacin and hydrocortisone, always bound better to the glyc-CDs with up to 180% increase in the stability constant. The degradation rate within the cyclodextrin cavity was not affected by the above derivation.
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  • 46
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    Reaction kinetics and catalysis letters 66 (1999), S. 71-77 
    ISSN: 1588-2837
    Keywords: Alumina ; alumina aerogel ; synthesis ; gelation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The synthesis of alumina aerogels has been carried out by hydrolysis of aluminium isopropylate as an aerogel precursor dissolved in isopropanol or methanol, followed by gelation of the sols obtained and drying under supercritical conditions and calcination. The influence of two main preparation parameters, precursor concentration and reagents (water to aluminium isopropylate) mole ratio, on the physicochemical properties of aerogels was investigated.
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  • 47
    ISSN: 1573-1111
    Keywords: crystalline inclusion compounds ; synthesis ; X-ray analysis ; 13C CPMAS NMR
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The structures of 1,4-bis(pyrazol-1'-yl)-2,3,5,6- tetrakis(3'',5''-dimethylpyrazol-1''-yl) benzene 1, its monohydrate, 1a, four 1 : 2 host : guest complexes, 1b–1e (acetic, propionic, pentanoic, and (±)-2-methyl butyric acids) and a di-picrate salt, 1f, have been determined by X-Ray analysis. In all complexes, in the salt and in the monohydrate compound, the host molecules are hydrogen bonded to two centrosymmetric related guests and to the water molecule which is disordered over two positions to mimic the inclusion complexes. In all compounds, the host exhibits Ci symmetry having the lone pair on the N(2) atom of each pyrazole pointing alternately upwards (u) and downwards (d) from the benzene ring. 1H and 13C NMR spectra of the free host 1 and of the complexes are consistent with the ududud conformation and the stoicheiometry of the inclusion compounds.
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  • 48
    ISSN: 1573-1111
    Keywords: unsymmetrical ditopic calixcrown ; synthesis ; crystal structure
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Consecutive base-catalysed reactions of calix[4]arene with the ditosylates of two different polyetherdiols result in the relatively efficient production of an unsymmetrical calix biscrown-6 which, after reduction of an ethoxycarbonyl substituent to an hydroxymethyl group, has been characterised structurally by a room-temperature, single crystal X-ray study of its chloroform solvate. Crystals of ( 4), C53H62O13... ∼0.57CHCl3, are triclinic, P¯1, a 18.95(3), b 12.394(9), c 11.756(7) Å α 106.93(5), β 101.77(8), γ 94.63(8)°, Z = 2; R was 0.088 for 2231 ’observed' (I 〉 3σ(I)) diffractometer data.
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  • 49
    ISSN: 1573-1111
    Keywords: P-pivot lariat ethers ; synthesis ; nucleophilic substitution ; metal ion complexation ; molecular receptors
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A series of hydrophopic ( 2 and 3) and new hydrophilic ( 4– 7) molecular receptors of the PNP-lariat ether with tetra-substituted cyclotriphosphazene subunits have been prepared by the complete nucleophilic substitution of chlorine atoms in the reactive PNP-crown precursor 1 with the respective sodium cation-paired oxyanions (phenoxy → 2, β-naphthoxy → 3, and methoxytrioxyethylenoxy → 4) and aliphatic amines (n-propylamine → 5 aziridine → 6, and pyrrolidine → 7). Their structures were established by MS and 31P NMR spectroscopy and their metal ion complexing properties tested by a TLC method. Comparison of the complexation behaviour for ligands 1– 7 shows that the affinity for particular cations is strongly substituent-dependent and, in general, is significantly enhanced by cooperation of the side arm donor atoms (O or N) with the parent PNP-crown structure in the binding process. The remarkable affinity of some ligands for selected cations, in particular lithium, cesium, and silver ions, is interpreted in terms of structure-property relationships.
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  • 50
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    Journal of inorganic and organometallic polymers and materials 8 (1998), S. 167-178 
    ISSN: 1572-8870
    Keywords: Poly(1,2-phenylenedithiocarbamate) ; poly(1,2-phenylenedithiocarbamate)–metal complexes ; synthesis ; characterization ; structure ; DC electrical conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Poly(1,2-phenylenedithiocarbamate) (PPDTC) was prepared by the reaction of 2-aminothiophenol with carbon disulfide followed by condensation through the removal of H2S gas. PPDTC was used as a ligand to prepare four poly(1,2-phenylenedithiocarbamate)–metal complexes of iron(II), cobalt(II), copper(II), and lead(II), by refluxing with the metal salts. The polymer and its metal complexes were investigated by elemental analyses, UV–visible and IR spectroscopy, inherent viscosity, and magnetic susceptibility. The DC electrical conductivity variation with the temperature in the range 298–498 K of PPDTC and its polymeric copper complex was measured. Both polymer and polymer metal complexes showed an increase in electrical conductivity with an increase in temperature: typical semiconductor behavior. The proposed structure of the complexes is (MLX2·mH2O) n .
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  • 51
    ISSN: 1572-8773
    Keywords: Gram-negative bacteria ; inositol ; mycobacteria ; siderophore analog ; synthesis ; tricatecholate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A novel 1,3,5-triamino-myo-inositol derivative ispresented as a readily available scaffold for the design oftripodal siderophore mimetics.Based on this scaffold, various hexadentate catecholate-type siderophoreanalogs weresynthesized by attaching the catechols to the inositol scaffold via spacer units of differentstruc-tureand length. The potential to tune the polarity of the inositol containing siderophoreanalogs has also beendemonstrated by varying the protection group strategy. The siderophoreactivity of the prepared siderophoreanalogs was examined by cross-feeding tests withvarious Gram-negative bacteria and mycobacteria.
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  • 52
    ISSN: 1572-8803
    Keywords: pyridine bases ; synthesis ; catalyst ; pentasil zeolite ; ZSM-5 ; shape selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pyridine bases are widely used in pharmaceuticals, insecticides, and herbicides due to their high bioactivity. In this paper, in addition to the conventional synthesis methods for pyridine bases, recent advances in the gas phase synthesis of pyridine bases over the shape selective catalysts (ZSM-5) are described.
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  • 53
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    Journal of thermal analysis and calorimetry 53 (1998), S. 285-296 
    ISSN: 1572-8943
    Keywords: alanine ; complexes of rare earth bromides ; synthesis ; TG-DTG ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The complexes of rare earth bromides with alanine, REBr3·3Ala·nH2O (RE=Ce, Pr, Sm, Eu, Gd and Tb, n=3; RE=Dy and Y, n=2.5 Ala=alanine), were prepared and characterized by means of chemical analysis, elemental analysis, molar conductivity, thermogravimetry, IR spectra and X-ray diffraction. The thermal decomposition in N2 of these complexes was studied by means of TG-DTG techniques from ambient temperature to 1000°C. During heating, the hydrated complexes of Ce, Pr and Y lose waters in one step, but the hydrated complexes of Sm, Eu, Gd, Tb and Dy lose waters in two steps. Then anhydrous complexes lose 2.5 alanine molecules except the complexes of Eu which lose three alanine molecules. Apparently, only be complex of Eu has an intermediate, EuOBr. All complexes finally decompose to oxides.
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  • 54
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    Journal of thermal analysis and calorimetry 53 (1998), S. 577-584 
    ISSN: 1572-8943
    Keywords: nicotinamide ; phenazone ; synthesis ; thermal decomposition ; zinc complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract New zinc complex compounds of general formula ZnL2,X2 {X=CI, Br; L=phenazone(phen), nicotinamide(nam)} were synthesized. The new compounds were characterized by elemental analysis, IR spectroscopy and DTA, TG/DTG methods. Thermal properties of the new compounds were investigated. It was found that nicotinamide, phenazone and ZnCl2 or ZnBr2 are released during the thermal decomposition of the compounds. Mass spectroscopy has been used for the determination of the thermal decomposition intermediate products.
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  • 55
    ISSN: 1572-9001
    Keywords: X-ray structure ; benzoxazine ; synthesis ; potassium channel modulators
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract With the aim of discovering new molecules with K+ channel modulating properties, we have synthesized analogues of cromakalim, an important molecule which shows specific affinity toward the K+ channels, by replacing the benzopyrane ring with a benzoxazine moiety. As a part of this study, we have synthesized and characterized, in solution and in the solid state as well, the compound ethyl [2,2-dimethyl-6-(Δ2-thiazolin-2-yl)-4H-l,4-benzoxazin-3-one-4-yl]butyrate (V). This compound exhibits in the solid state the following parameters: molecular formula C19H24N2O4S, triclinic, space group $$P\bar 1$$ , Mw = 376.5, a = 12.581(3) Å, b = 5.485(4) Å, c = 14.612(2) Å, α = 91.85(2), β = 108.9(3), γ = 82.04(4), V = 944.7 Å3, Z = 2, d = 1.323 g·cm−3. We describe here the synthesis and discuss the solid-state conformation of this new molecule; when tested on rat aorta ring precontracted with phenylephrine, the compound showed a concentration-dependent relaxation comparable to that measured for cromakalin taken as reference drug.
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  • 56
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    Molecular diversity 4 (1998), S. 149-153 
    ISSN: 1573-501X
    Keywords: combinatorial ; cyclic peptides ; cyclization ; dipeptides ; diversity ; macrocycles ; orthogonally protected lysine ; solid phase ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A simple and efficient synthesis of novel 14-membered macrocycles from a resin-bound orthogonally protected lysine residue is described. Reductive alkylation of the lysine α-nitrogen introduces the first diversity element. Acylation of the resultant secondary amine with an Fmoc-amino acid introduces the second diversity element providing a resin-bound protected di-peptide precursor. Removal of the Fmoc-group is followed by acylation with a succinic anhydride to introduce the final diversity elements. Removal of the methyltrityl-group from the amino group followed by macrocyclization provides the desired macrocycles, after TFA cleavage, in excellent yield and purity.
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  • 57
    ISSN: 1573-4986
    Keywords: glycopeptide ; synthesis ; T cell ; immune response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The 2-bromoethyl β-glycosides of the disaccharide galabiose [Gal(α1-4)Gal] and the trisaccharides globotriose [Gal(α1-4)Gal(β1-4)Glc] and 3′-sialyllactose [Neu5Ac(α2-3)Gal(β1-4)Glc] have been prepared by improved routes. The 2-bromoethyl glycosides were then used in cesium carbonate promoted alkylations of the sulfhydryl groups of cysteine and homocysteine residues in T cell stimulating peptides. This convergent and general approach was used to prepare 16 neoglycopeptides which were obtained in 52–95% yields after purification by HPLC. 1H NMR spectroscopy revealed that β-elimination and epimerization of neoglycopeptide stereocentres did not occur during the synthesis.
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  • 58
    ISSN: 1573-4986
    Keywords: CMP-Neu5Ac analogues ; synthesis ; sialyltransferase inhibitors ; sialyltransferase assay ; α(2-6)-sialyltransferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Quinic acid (4) was transformed into phosphitamides 6, 14, and 15, which could be readily linked to 5′-O-unprotected cytidine derivative 7; ensuing oxidation of the obtained phosphite triesters with tert-butylhydroperoxide furnished the corresponding phosphate triesters 8, 16, and 17, respectively. Hydrogenolytic debenzylation of the phosphate moiety, base catalysed removal of acetyl protective groups, and basic hydrolysis of the methylester of the quinic acid moiety furnished CMP-Neu5Ac analogues 1-3. In order to measure their inhibition of sialyltransferases, a nonradioactive sialyltransferase assay [employed for α(2-6)-sialyltransferase from rat liver (EC 2.4.99.1)] based on reversed-phase HPLC separation of UV-abelled acceptor 20 (p-nitrophenyl glycoside of N-acetyllactosamine) from the UV-labelled product 21 (p-nitrophenyl glycoside of sialyl α(2-6′)-N-acetyllactosamine) and p-nitrophenylalanine as internal standard was developed. The assay reproduced the reported KM values for CMP-Neu5Ac and N-acetyllactosamine and the Ki values for CDP. 1 and 2 turned out to be potent sialyltransferase inhibitors. © 1998 Rapid Science Ltd
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  • 59
    ISSN: 1573-4986
    Keywords: enzymic sialylation ; glycosphingolipid ; GM3 ; GM3 analog ; lyso-GM3 ; lyso-GM3 analog ; modified polyacrylamide ; photolysis ; polymer support ; sialyltransferase ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two water-soluble polymers, carrying 0.24 meq g−1 of lactosyl-β(1-1)-sphingosine (7) and 0.13 meq g−1 of lactosyl-β(1-3)-sphingosine (8) were prepared. The polymers served as acceptors in the α-(2-3)-sialyltransferase reaction (up to 55.3 and 38.5% transfer yields, respectively). Subsequent photolysis, released compounds 11 (lyso-GM3) and 12 (lyso-GM3 analog), respectively; acylation and chromatography afforded (5-acetamido-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonic acid)-(2-3)-β-D-galactopyranosyl-(1-4)-β-D-glucopyranosyl-(1-1)-(2S, 3R, 4E)-2-octadecanoylamino-4-octadecene-1,3-diol (13, GM3) and (5-acetamido-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonic acid)-(2-3)-β-D-galactopyranosyl-(1-4)-β-D-glucopyranosyl-(1-3)-(2S, 3R, 4E)-2-octadecanoylamino-4-octadecene-1,3-diol (14, GM3 analogue), respectively, thus presenting a route to glycosphingolipids possessing the unusual glycosyl-β(1-3)-spingosine linkage.
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  • 60
    ISSN: 1435-1536
    Keywords: Key words Conducting polymer ; polypyrrole ; silica ; nanocomposite ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  The effect of varying the oxidant, monomer and silica sol concentrations, silica sol diameter, polymerization temperature, stirring rate and oxidant type, on the particle size, polypyrrole content and conductivity of the resulting polypyrrole– silica colloidal nanocomposites has been studied. Surprisingly, nanocomposite formation appears to be relatively insensitive to most of the above synthesis parameters. One synthesis parameter which does have a significant and reproducible effect is the stirring rate: smaller, more monodisperse nanocomposite particles are obtained from rapidly stirred reaction solutions. However, this effect is only observed for the (NH4)2S2O8 oxidant. An alternative oxidant, H2O2/Fe3+, was found to give nanocomposites of similar particle size, polypyrrole content and conductivity to those obtained using the (NH4)2S2O8 oxidant. The colloid stability of these polypyrrole–silica nanocomposite particles depends on their silica content. The colloid stability of a silica-rich nanocomposite prepared using the (NH4)2S2O8 oxidant in the presence of electrolyte was comparable to that of a silica sol, whereas a polypyrrole-rich nanocomposite prepared using FeCl3 had markedly poorer colloid stability under these conditions. These observations are consistent with a charge stabilization mechanism for these nanocomposite particles.
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  • 61
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    Colloid & polymer science 276 (1998), S. 662-668 
    ISSN: 1435-1536
    Keywords: Key words Liquid crystal polymers ; ionogenic polymers ; synthesis ; hydrogen bond ; order parameter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  A series of new ionogenic liquid crystalline (LC) copolymers (A4CB-AA) was prepared by radical copolymerization of 4-(4-cyanobiphenyl-4′-yloxy) butyl acrylate (A4CB) and acrylic acid (AA). The presence of the AA units do not prevent the development of the nematic phase, which is typical of the initial cyanobiphenyl homopolymer. At a content of AA of 42–52 mol%, the copolymers produce the S Ad type of mesophase, and this phenomenon is explained by an increased rigidity of the main chain due to the development of intramolecular hydrogen bonds. By increasing the concentration of AA units higher than 55 mol%, the development of mesophase is prevented, and the as-received copolymers are amorphous. A crucial role of intramolecular hydrogen bonds for the development of the S A phase in the copolymers is proved by synthesizing and studying the copolymers, in which the same type of the mesogenic group A4CB is preserved but the second component is provided by methyl ether of acrylic acid; such copolymers are able to produce only a nematic phase. Studying orientation of LC A4CB-AA copolymers in the magnetic field by the method of wide-line 1H NMR spectroscopy allows one to calculate the temperature dependences of order parameter S and to advance a correct interpretation of experimental data.
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  • 62
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    Journal of porous materials 5 (1998), S. 121-126 
    ISSN: 1573-4854
    Keywords: TiO2-pillared saponite ; synthesis ; pore size distribution ; UV-Vis reflectivity ; TG-DTA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The preparation of TiO2-pillared saponite was carried out in a CH3COOH aqueous solution. Titanium ion species to intercalate into the interlayer of saponite were obtained by an addition of Ti(C3H7O)4 to an aqueous solution of CH3COOH and by subsequent aging of the solution for a prescribed time. Ti4+-intercalated saponite including organic materials was obtained by ion exchange. After the sample was calcined at 500°C in air, TiO2-pillared saponite was obtained. The resulting TiO2-pillared saponite (Ti-Sapo) possessed surface areas in the range 300–400 m2/g and a sharp pore size distribution with the pore radius of 1.2 nm. The basal spacing of the product heated at temperature 〉250°C was about 2.45 nm. The pillar height of TiO2 in the Ti-Sapo was estimated to be 1.5 nm.
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  • 63
    ISSN: 1573-904X
    Keywords: bisphosphonates ; tetracycline ; calcification ; hydroxyapatite ; bone resorption ; synthesis
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. This work was aimed at synthesizing novel bisphosphonates (BPs) and examining them in comparison to clinically used BPs such as pamidronate and alendronate, and to tetracycline, in order to evaluate their potential as anticalcification and antiresorption agents. The correlation between the various models was examined in order to establish facile experimental models for pre-screening of potential compounds. Methods. Nitrogen-containing heterocyclic, novel BPs such as 2-(3-methylimidazolio) ethylidene-l,l-bisphosphonic acid betaine (VS-5b), 2-(2-dimethylamino-4-pyrazinio)ethylidene-1,1 -bisphosphonic acid betaine (VS-6b), and 2-(2-α-pyridylethylthio) ethylidene-1,1-bisphosphonic acid (ISA-225), were synthesized and evaluated in comparison to clinically used BPs, in various experimental models of resorption and calcification. Results. The physicochemical properties of the novel compounds are slightly different than the BPs in clinical use: the pKa values are lower, the affinity for hydroxyapatite is lower and the solubilities of the calcium salts are higher. The anticalcification potencies of the novel compounds were high and ranked as follows: alendronate = pamidronate 〉 VS-6b = VS-5b = ISA-225 〉 tetracycline. The in vivo antiresorption activity of VS-5b and VS-6b in comparison to that of the clinically employed, pamidronate, was shown to be similar and higher, respectively. Conclusions. The anticalcification activity of the novel compounds as well as that of tetracycline was lower than that of alendronate. The antiresorption activity of VS-6b was similar to that of pamidronate. A good correlation between the different models was found, enabling the facile screening of novel compounds. The activities of tetracycline and EDTA highlight the distinct behavior of BPs as "crystal poison”. In addition, tetracycline was found to be a potent anticalcification agent in the ectopic calcification model.
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  • 64
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    Journal of inclusion phenomena and macrocyclic chemistry 30 (1998), S. 29-43 
    ISSN: 1573-1111
    Keywords: SPV-B24C8 copolymer ; synthesis ; ion-selective electrodes ; potassium
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A synthetic procedure has been developed for the preparation of styrene/4'-vinyl-benzo-24-crown-8 copolymer (SPV-B24C8). The resulting copolymer was used as a membrane carrier to construct a K+ ion-selective electrode. The electrode exhibits a Nernstian response for K+ ions over a wide concentration range. The nature of the plasticizer, the additive, the concentration of internal solutions in the electrodes and the composition of the membrane were investigated. The performance of the electrode in terms of electrode reproducibility, response stability and regeneration was also studied. The selectivity coefficients of the electrode for potential interferents including alkali, alkaline earth, some transition and heavy metal ions were found to be in the order of 10-3 or less. The electrode was successfully used for the determination of potassium ion in blood serum.
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  • 65
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    Journal of inorganic and organometallic polymers and materials 7 (1997), S. 1-18 
    ISSN: 1572-8870
    Keywords: Alternating copolymers ; cis and trans stilbenes and oligomeric dimethylsilylenes ; synthesis ; spectral properties ; photoisomerization and degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A series of perfectly alternating copolymers containing oligomeric dimethylsilylene and cis or trans stilbene units has been prepared by the condensation polymerization of silyl ditriflates with the corresponding stilbene dianion. As expected, the spectral characteristics and the polymer processability were very different for the isomeric polymers. Evidence of σ–π interaction was obtained from absorption measurements and the excited state of the Si4 catenates was characteristic of a polar charge transfer state. The polymers are all photoactive and irradiation in the long-wavelength absorption band leads to cis–trans isomerization followed by complete disappearance of the long-wavelength (λ〉300 nm) absorption. The latter was not observed for the monomeric model compounds.
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  • 66
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    Topics in catalysis 4 (1997), S. 249-260 
    ISSN: 1572-9028
    Keywords: mesoporous materials ; synthesis ; pore size ; activity ; selectivity
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The development of ordered mesoporous solids is revised. Acid, base, and redox catalytic properties are presented together with their application for a series of organic reactions of fundamental and practical interest. Finally it is explained that it is possible to make use of the high surface and regular porosity of MCM–41 to prepare supported metals, and bifunctional catalysts. The above properties together with the presence of a large number of surface silanol groups allow the grafting of catalytically active transition metal complexes.
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  • 67
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    Journal of thermal analysis and calorimetry 50 (1997), S. 785-793 
    ISSN: 1572-8943
    Keywords: double sulfates ; lanthanides ; synthesis ; thermal studies
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    Topics: Chemistry and Pharmacology
    Notes: Abstract On evaporation at room temperature of an aqueous reaction mixture of Ln(III) sulfate and ethanolammonium sulfate in a molar ratio higher than 1∶16, crystal products with a waxy feel were obtained. They were identified by means of the X-ray powder diffraction patterns and it was concluded that they are isostructural. The results of elemental analysis and the mass losses by TG analysis indicated the formation of double sulfates with general formula: (HOCH2CH2NH3)4Ln2(SO4)5·4.5H2O (Ln=La, Ce, Pr or Nd) Their thermal decompositions in static atmosphere in the temperature range from ambient up to 1173 K took place in a similar way, and mainly Ln2O2SO4 was obtained as final product. The exception was the Ce compound, which decomposed to CeO2. The double sulfates decomposed in many not well-differentiated steps. From the mass losses occurring during thermal decomposition, the mode of thermal decomposition was presumed. The X-ray powder diffraction patterns of Ln2O2SO4 (Ln=La, Pr and Nd) show that they are also isostructural.
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  • 68
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    Journal of thermal analysis and calorimetry 49 (1997), S. 1255-1261 
    ISSN: 1572-8943
    Keywords: barium cerate ; oxalate coprecipitation ; proton conductor ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The decomposition process of barium, cerium and neodymium oxalates in air was investigated by DTA-TG. Decomposition of an oxalate coprecipitate precursor and formation of barium cerate were examined in air, N2 and CO2 atmospheres, respectively, by employing DTA-TG and XRD. The results showed that, in air, cerium oxalate could easily be decomposed to CeO2 below 350°C and Nd2O3 could be obtained at 670°C, while a high temperature of 〉1400°C was needed to obtain BaO. Although some amount of BaCeO3 was formed at 500°C in air, at 650°C in N2 and at 800°C in CO2, single perovskite phase of BaCeO3 could only be obtained at a much higher temperature.
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  • 69
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    Molecular and cellular biochemistry 173 (1997), S. 1-5 
    ISSN: 1573-4919
    Keywords: human ; cytotrophoblast ; syncytiotrophoblast ; culture ; iso-transferrins ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Transferrin (Tf) mRNA was recently demonstrated in rat and mouseplacental tissue. Rat placental cells were shown to secrete transferrin. Thecell type with which Tf mRNA was associated was not investigated. Wetherefore studied the ability of immunopurified human term cytotrophoblastcells in culture to synthesize Tf, by means of pulse-label experiments with35S-methionine and report that these cells do synthesize Tf. Tf mRNA wasdemonstrated in the cell lysates by means of RT-PCR. Tf isolated fromcytotrophoblast and syncytiotrophoblast cells was shown to be different fromboth maternal and fetal serum Tf with respect to the distribution ofisoforms as demonstrated by means of iso-electric focusing. The iso-electricpoints were found at lower pH values (pH 5.0-5.4), compared to theiso-electric points of maternal and fetal serum Tf, suggesting a higherdegree of sialylation and glycan chain complexity.
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  • 70
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    Journal of sol gel science and technology 8 (1997), S. 831-836 
    ISSN: 1573-4846
    Keywords: aerogel ; silica-zirconia ; synthesis ; sintering ; pore distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A solution of zirconium propoxide stabilized by methoxyethanol is mixed with silicon ethoxide in ethanol and hydrolyzed by small amounts of neutral, basified or acidified water. The obtained silica-zirconia gel is dried in supercritical conditions, yielding an aerogel. The modifications of the aerogel porous texture as a function of chemical composition and thermal treatment are investigated using adsorption-desorption isotherms analysis, mercury porosimetry, electron-microscopy and X-ray diffraction.
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  • 71
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    Journal of sol gel science and technology 8 (1997), S. 831-836 
    ISSN: 1573-4846
    Keywords: aerogel ; silica-zirconia ; synthesis ; sintering ; pore distribution
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A solution of zirconium propoxide stabilized by methoxyethanol is mixed with silicon ethoxide in ethanol and hydrolyzed by small amounts of neutral, basified or acidified water. The obtained silica-zirconia gel is dried in supercritical conditions, yielding an aerogel. The modifications of the aerogel porous texture as a function of chemical composition and thermal treatment are investigated using adsorption-desorption isotherms analysis, mercury porosimetry, electron-microscopy and X-ray diffraction.
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  • 72
    ISSN: 1573-4986
    Keywords: Glycoside ; synthesis ; cancer ; hexamethylmelamine ; methylol ; formaldehyde ; modelling ; deacetylation ; triazine ; N-hydroxymethyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The synthesis of analogues of the anti-tumour drug 2-[N-(hydroxymethyl)methylamino]-4,6-bis (dimethylamino)-1,3,5-triazine (HMPMM) in which the OH or a dimethylamino group is replaced by a carbohydrate has been explored. Triazinyl β-glycosides were readily prepared by reaction of sugars with trimethyl-triazinylammonium salts. These were made with one or two methylamino groups on the triazine for reaction with formaldehyde to give the cytotoxic NMeCH2OH group. However, reaction of the triazinyl glycosides with formaldehyde gave complex intractable mixtures. When the carbohydrate portion was changed to the fully protected 2,3,4,6-tetra-O-acetyl glucose a good yield of the 2-[N-(hydroxymethyl)methylamino]-4-(dimethylamino)-1,3,5-triazin-2-yl tetra-O-acetyl β-glucoside was obtained. However, de-acetylation using sodium methoxide also removed the N–CH2OH group. We are investigating protection of the base-sensitive N–CH2OH group as trialkylsilyl and benzyl ethers and are looking at de-acetylation methods that are more selective. We have prepared glycosides in which the sugar is joined through the oxygen of the NMeCH2OH group. Coupling of acetobromoglucose with HMPMM catalysed by silver salts was not successful. Although methyl and cyclohexyl derivatives of HMPMM may be produced in high yields by reaction of HMPMM with methyl and cyclohexyl alcohols under acidic catalysis, production of glycosides in this way gave poor yields. MNDO calculations on reactions of HMPMM helped us devise improved reaction conditions for the condensation of 2,3,4,6-tetra-O-acetyl glucose with HMPMM and its derivatives. The best procedure to generate one of the target glycosides is to react 2,3,4,6-tetra-O-acetyl glucose and formaldehyde with 2-methylamino- 4,6-bis(dimethylamino)-1,3,5-triazine. The β-glycoside product was de-acetylated using potassium carbonate in dry methanol. Abbreviations: HMM, hexamethylmelamine (2) or 2,4,6-tris(dimethylamino)-1,3,5-triazine; HMPMM, hydroxymethylpentamethylmelamine or 2-[N-(hydroxymethyl)-methylamino]-4,6-bis(dimethylamino)-1,3,5-triazine; PMM, Pentamethylmelamine or 2-methylamino-4,6-bis(dimethylamino)-1,3,5-triazine; TBMS, t-Butyldimethylsilyl; p-TSA, p-Toluenesulphonic acid
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  • 73
    ISSN: 1573-4854
    Keywords: mesoporous silica ; hexagonal phase ; synthesis ; room temperature ; inorganic silicate sources ; acidic medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The room-temperature synthesis of mesoporous silica was investigated by using cationic surfactants and inorganic Si sources, like sodium silicate and colloidal silica. Mesoporous silica analogous to the hexagonal MCM-41 could be obtained over a wide range of pH below ca. 11 within short synthesis time (3 h), when the Q4-state Si was absent in the Si source solution prior to mixing with an aqueous solution of cationic surfactants. It was suggested that the strongly acidic conditions (pH 〈 1) were favorable to give mesoporous silica materials with higher surface area and larger mesopore volume.
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  • 74
    ISSN: 1572-9001
    Keywords: Azoxyfurazan ; ballistic modifier ; diaminofurazan ; energetic material ; explosive ; synthesis ; X-ray analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The synthesis of the energetic compound 4-[(4-nitro-1,2,5-oxadiazol-3-yl)-NNO-azoxyl]-1,2,5-oxadiazol-3-amine (3) was achieved in two steps from diaminofurazan (1). Compound 3 was characterized by X-ray diffraction. From the X-ray structure a bifurcated intramolecular H bond between O(2)-H(2)-N(4) was observed. In addition, intramolecular H bonding was observed between H(1) and N(7)′ of an adjacent molecule. One molecule of ethanol and one-half molecule of water per molecule of3 was observed in the crystal lattice. However, no H bonding was observed between the solvent molecules and3 in the crystal lattice. Despite the presence of solvent in the crystal lattice,3 was found to have a high crystal density (d=1.856 g/cm3).
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  • 75
    ISSN: 1573-4846
    Keywords: synthesis ; 1H NMR ; 13C NMR ; gas chromatogram/mass spectrum ; hybridized silicon alkoxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Using silicon tetrachloride (SiCl4), tert-butanol (t-BuOH), ethanol (EtOH) and NH3, the hybridized silicon ethoxide 3-tert-butoxide (Si(OEt)x(OBut)4-x) was synthesized and the configuration of the material was investigated by FT-IR,1 H and 13C NMR and gas chromatogram/mass spectrum (GC/MS) techniques. The results confirm that both the ethoxy and the tert-butoxy groups have been attached to silicon atoms. Furthermore, the alkoxy group types and their relative amounts in the alkoxide were also determined by 1H and 13C NMR and GC/MS.
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  • 76
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    Journal of inclusion phenomena and macrocyclic chemistry 29 (1997), S. 175-185 
    ISSN: 1573-1111
    Keywords: p-tert-Butylcalix[5]arene ; synthesis ; complexation ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The formation of p-tert-butylcalix[5]arene by the opening ofp-tert-butyldihomooxacalix [4]arene and the addition of a monomer has beenstudied. Various facets, including the effects of bases and the nature ofthe monomer added to the p-tert-butyldihomooxacalix[4]arene, have beeninvestigated. p-tert-Butylcalix[5]arene can be prepared in yields up to30%. The structure of its 1 : 2 complex with DMF has been determinedby X-ray crystallography. Crystals are triclinic, space group P¯1, a =1428.2(3) pm, b = 1837.3(3) pm, c = 1276.1(2) pm, α = 108.98(1)°,β = 105.02(2)°, γ = 95.21(1)°, Z = 2, D c = 1.059 kg m-3,final R value = 0.087. The macrocycle adopts a cone conformation, one guestenclosed inside the cavity, the other one outside.
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  • 77
    ISSN: 1572-8870
    Keywords: Phosphazenes ; coordination chemistry ; synthesis ; electrochemical behavior ; transition metal ; cinnamonitrile cyclophosphazene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hexakist 4-formylphenoxy cyclophosphazene (1) reacts with six equivalents of cyanomethylenetriphenylphosphorane to give hexakist 4-cinnamonitrile cyclotriphosphazene bearing 12 functional groups tsix nitriles and six olefins' able to coordinate up to 12 metals. In this way a series of polynuclear phosphazene metal derivatives (8–12) was prepared with different transition metals and in different oxidation states. Pt(0), Pt(II) and Rh(I). The analogous cinnamonitrile derivatives (3–7) were prepared and used as models for the characterization of corresponding phosphazene compounds. The redox properties of the complexes3–5 and8–10 as well as of the free cinnamonitrile2 and the free substituted cyclophosphazene1 have been investigated by cyclic voltammetry (CV) and controlled potential electrolysis (CPE) in aprotic media (THF, CH2Cl2, or NCMe 0.2M [NBu4][BF4]), at Pt electrodes. Cathodic processes have been detected only when the unsaturated C=C bond of the cinnamonitrile group is uncoordinated: hence, for compounds1. 4. and9. they are irreversible occur at potentialsE p red ca. −1.3 to ca. −1.9V vs SCE which are less cathodic than that exhibited by the free cinnamonitrile (2:E p red ca. −2.0 V vs SCE), and are believed to be centered at the electron-acceptor emptyπ * (C=C) orbital of each of the cinnamonitrile groups present in the molecule. Anodic processes are displayed only by complexes3. 5. 8. and10 with at least one Pt(0) site: they are irreversible, conceivably centered at such a metal center, and occur at potentials (E p bv ca. 0.7 1.2 V vs SCE) which are dependent on the electronic effects of the ligands, in particular the strong electron-withdrawing ability of the cyclophosphazene group. Complex10 undergoes dissociation in NCMe to form9 and possibly solvated [Pt(PPh3)2] species which adsorb at the electrode surface. No evidence for any redox process centered at the phosphazene ring has been found.
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  • 78
    ISSN: 1572-8773
    Keywords: chrysobactin ; Erwinia chrysanthemi ; immunoassay ; siderophore ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Chrysobactin (α-N-(2,3-dihydroxybenzoyl)-d-lysyl-l-serine), a siderophore that is essential for systemic virulence by plant pathogenic Erwinia chrysanthemi, was synthesized with high diastereomeric purity. Chrysobactin was prepared by coupling the N-hydroxysuccinimide ester of α-N-(2,3-dibenzyloxybenzoyl)-ε-N-Cbz-d-lysine with l-serine benzyl ester followed by deprotection via hydrogenolysis. Optically pure chrysobactin was obtained with 98% overall yield. A monoclonal antibody to ferric chrysobactin was developed and characterized as IgM. The antibody reacts with chrysobactin, ferric chrysobactin and less strongly with ferric dihydroxybenzoic acid. The antibody reacts weakly with the siderophores ferrichrome, A, ferric pseudobactin and ferric rhodotorulic acid. This antibody was used in a competitive immunoassay to detect ferric chrysobactin at 10−8 to 10−10 mol. This immunoassay may provide a useful method for the detection of chrysobactin in plant samples.
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    Catalysis letters 38 (1996), S. 245-249 
    ISSN: 1572-879X
    Keywords: ferri-silicate ; gallo-silicate ; zeolites ; molecular sieves ; synthesis ; mesitylene isomerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ferri- and gallo-silicate analogues of NCL-1, a high silica large pore zeolite, have been synthesized and characterized through spectroscopic methods (XRD, IR, ESR and solid state MAS NMR), ion exchange capacity, adsorption (n-hexane, 1,3,5-trimethylbenzene and water), BET surface area and catalytic activity and selectivity in Brønsted acid catalyzed conversion of 1,3,5trimethylbenzene measurements. These data were compared with those exhibited by Al-NCL-1 analogue. During 1,3,5-trimethylbenzene (mesitylene) isomerization into 1,2,4-trimethylbenzene (pseudocumene), the conversion decreased in the order: Al〉 Ga-〉 Fe-NCL-1 (at the same reaction temperature, WHSV and time on stream). However, the selectivity for pseudocumene and isomerization selectivity (vis-á-vis disproportionation) followed the reverse order at comparable conversion level.
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  • 80
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    Journal of thermal analysis and calorimetry 46 (1996), S. 515-520 
    ISSN: 1572-8943
    Keywords: SiO2-aerogel ; synthesis ; thermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Aerogels are extremely porous high-tech materials based on inorganic oxides, especially silica. The paper describes synthesis and properties of SiO2-aerogel, and changes occurring during heating of SiO2-aerogel in the temperature range from 20 to 1000°C. Four thermoanalytical methods were used: Thermodilatometry, Differential thermal analysis, Thermogravimetry and Derivative thermogravimetry.
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  • 81
    ISSN: 1573-9171
    Keywords: stannyl-substituted ; 1-germacyc lope nta- 2,4-diene ; stannyl-substituted 1-germacyclopent-3-ene ; synthesis ; reactivity ; photolysis ; germanium-tin bond cleavage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Previously unknown stannyl-substituted germanium heterocycles, 1, 1 -bis(trimethylstannyl) 2,3,4,5-tetraphenyl-l-germacyclopenta-2,4-dienc and 1,1-bis(trimethylstannyl)-3,4-dimethyl-1-germacyclopent-3-ene were synthesized, and their photolysis and chemical transformations were Studied.
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  • 82
    ISSN: 1573-9171
    Keywords: alkylferrocenes ; alkylferrocenium cations ; synthesis ; cyclopalladation ; micellar media ; electrochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Absract Simple methods have been developed for the preparation of a series ofn-alkylferrocenes H(CH2) n Fc (n = 3, 5–8, or 12) based on Friedel-Crafts acylation of ferrocenes followed by reduction of the corresponding ketones with Zn amalgam. The properties of H(CH2) n Fc and the corresponding ferrocenium ions in micellar aqueous solutions and the behavior of water-soluble cations H(CH2) n Fc+ in the absence of micelles were studied by cyclic voltammetry. In all cases, the formal redox potentials of ferrocenes (E o′) increase linearly asn increases up to 8. Whether micelles are present or not, the corresponding correlation equation has the following form:E o′= α + βn, where β = 29 mV in all cases. The synthesis of (±)-1-ethyl-2-methylferrocene from racemic α-dimethylaminoethylferrocene is reported.
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  • 83
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    Russian chemical bulletin 45 (1996), S. 623-629 
    ISSN: 1573-9171
    Keywords: (S)-prolinol ; chiral 1-amino-1,3-dienes ; generation andin situ transformation ; chiral cyclohexa-1,3-dienes and hexahydronaphthalenes ; synthesis ; monoalkylidenemalonates ; [4+2] cycloaddition ; stereoselectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 3-Methyl- and 3-phenylbut-2-enal in the presence of (S)-prolinol (0.1 eq.) in benzene or THF react with the acidic monoesters of alkenylidene, and arylmethylidene-, and alkylidenemalonic acids at −10 to +22 °C to give optically active esters of 4,6-disubstituted cyclohexa-1,3-diene-l-carboxylic acids in moderate (10–43 %) yields. The enantiomeric purity of the products formed from the lint two types of acidic ylidenemalonates varies from 28 to 68 % and is higher than that observed in the case of related alkylidenemalonates. Under similar conditions cyclohexylideneacetaldehyde affords optically active derivatives of 1,5,6,7,8,8a-hexahydronaphthalene as mixtures ofcis andtrans isomers. The enantiomeric purity and absolute configuration of the cyclohexadienes thus obtained were determined using1H NMR spectroscopy in combination with chiral solvating agents.
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  • 84
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    Russian chemical bulletin 45 (1996), S. 654-661 
    ISSN: 1573-9171
    Keywords: crown ether styryl dyes ; synthesis ; complexation ; anion-“capped” complexes ; [2+2] photocycloaddition ; cyclobutane derivatives ; 1H NMR spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract New crown ether styryl dyes (trans-1c,d) containing the 18-crown-6 ether fragment were synthesized. Interaction oftrans-1c,d dyes, as well as their analogs,trans-1a,b containing the 15-crown-5 ether fragment, with Ca(ClO4)2 in MeCN afforded supramolecular structures (dimeric complexes). Competing reactions,trans-cis-photoisomerization with the formation of anion-“capped” complexes ofcis-1a—d and [2+2] autophotocycloaddition with the formation of cyclobutane derivatives8a—d and9c, were observed on photolysis of solutions of complexes oftrans-1a—d with Ca2+. Preorganization oftrans-isomers in dimeric complexes with Ca2+ determined the regio- and stereoselectivity of each of the two directions of the photocycloaddition and the efficiency of the reaction.
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  • 85
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    Russian chemical bulletin 45 (1996), S. 667-670 
    ISSN: 1573-9171
    Keywords: long-chain 2-alkadiynylpyridines ; synthesis ; Langmuir-Blodgett films
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Four pathways of synthesis of 1-(2-pyridyl)heptacosa-12,14-diyne, using 10-bromodecan-1-ol and acetylene or tetradec-1-yne and 2-methylbut-3-yn-2-ol along with α-picoline as initial compounds, were studied and compared. It was shown that direct introduction of a completely formed unsaturated hydrocarbon chain into an α-picoline molecule by alkylation of its lithium derivative is the most appropriate method for preparation of long-chain 2-alkadiynylpyridines.
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  • 86
    ISSN: 1573-9171
    Keywords: ansa-zirconocene dichlorides ; synthesis ; molecular structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A mixture ofrac- andmeso-2,2′-propylidene-bis(η5-indenyl)zirconium dichlorides was obtained in 95% yield. The compounds were separated, and their structures were established by X-ray structural analysis.
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  • 87
    ISSN: 1573-9171
    Keywords: sodium alkyls ; lithium alkyls ; NMR ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 1H,23Na, and7Li NMR spectra of 2-ethyl hexylsodiurn, 2-ethylhexyllithium, and isobutyllithium obtained in the reaction of the corresponding alkyl chlorides and metals have been recorded. The1H N MR signal for the protons of the CH2Na group is shifted upheld compared with that for the protons of the CH2Li group (doublets at δ -0.88 and δ -0.83, respectively). The composition of the products of reaction of 2-ethylhexyl chloride with sodium depends on the form of the metal reagent employed. The use of sodium balls with diameter up to 2 mm results in the formation of products containing ionic chlorine (30–50 % with respect to Na); the reaction with the dispersion proceeds faster and the reaction product is chlorine-free. The23Na NMR spectra of these substances are also different, which is explained by the formation of 2-ethylhexylsodium complexes with NaCl in the former case.
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  • 88
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    Russian chemical bulletin 45 (1996), S. 901-910 
    ISSN: 1573-9171
    Keywords: carbofunctional silacyclobutanes ; alcohols ; trimethylsilyl ethers ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A four-step synthesis of 1-(ω-ydroxyalkyl)- and 1-(4-hydroxyphenyl)silacyclobutanes was carried out. The influence of the structure of the initial compounds and the reaction conditions on the ratio of the reaction products formed was studied. The stability of the silacyclobutane alcohols and the hydrolysis of their trimethylsilyl ethers were investigated.
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  • 89
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    Russian chemical bulletin 45 (1996), S. 911-913 
    ISSN: 1573-9171
    Keywords: carbofunctional silacyclobutanes ; alcohols ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Speier rearrangement was used for the synthesis of l-(ω-hydroxyalkyl)- and l-(4-hydroxyphenyl)silacyclobutanes.
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  • 90
    ISSN: 1573-9171
    Keywords: 2-nitroethanol ; sodium salt ; 2-oxo-3-hydroxypropionic acid oxime ; sodium salt ; 2-bromo-2-nitropropane-1,3-diol ; 2,2-dinitropropane-1,3-diol ; synthesis ; X-ray analysis ; molecular structure, stereochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A novel reaction of the sodium salt of 2-nitroethanol in aqueous ammonia resulted in the sodium salt of 2-oxo-3-hydroxypropionic acid oxime (1) has been found. Bromination of1 affords 2-bromo-2-nitropropane-1,3-diol (2) with a previously unknown molecular conformation. The formation mechanisms of compounds1 and2 were suggested. X-ray analysis of products1,2 and that of the model compound, 2,2-dinitropropane-1,3-diol, was performed.
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  • 91
    ISSN: 1573-9171
    Keywords: metallofullerenes ; synthesis ; chirality ; platinum ; cluster ; electronic absorption spectra ; 31P NMR spectra ; X-ray analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A novel optically active exo-metallofullerene derivative, η2-C60Pt[(+)-DIOP] (1) (DIOP is 2,3-o,o'-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphinobutane)), is formed as a result of the cleavage of the chelate metallocycle in Pt[(+)-DIOP]2 and the substitution of the bidentate (+)-DIOP ligand with C60. Cluster 1 was also obtained by replacement of the phosphine ligands in η2-C60Pt(PPh3)2 by (+)-DIOP. Compound 1 was identified by its electronic absorption spectra,31P NMR spectra, and the elemental analysis data. A singlecrystal X-ray study of the 1 cyclooctene solvate, η2-C60Pt[(+)-DIOP] C8H14 was performed. Packing of the fullerene cores in a crystal of 1 · C8H 14 corresponds to the diamond structure subjected to the significant orthorhombic distortions.
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  • 92
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    Russian chemical bulletin 45 (1996), S. 1232-1234 
    ISSN: 1573-9171
    Keywords: sterically hindered 2-propargyl-1,3-diketones ; aminomethylation ; synthesis ; copper(1) ; catalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 2-Propargyl-substituted methoxy-1,3-diketones react with alkoxymethylamines or paraform and secondary amines in the presence of CuCl at the acetylene group to afford Mannich bases.
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  • 93
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    Russian chemical bulletin 45 (1996), S. 1490-1491 
    ISSN: 1573-9171
    Keywords: carborane-containing ketones and enols ; synthesis ; isoncrization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A carborane-containing stable simple enol — 1-2-isopropyl-o-carboran-I-yl)-1-phenyl2-mesityl-2-lrydroxyctlrylcne — has been synthesized. This enol does not isomerize to the starting ketone or keto-enol mixture even after prolonged heating in benzene in the presence of CF3COOH.
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  • 94
    ISSN: 1573-9171
    Keywords: arenecyclopentadienyl complexes of ruthenium ; synthesis ; electrochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A series of are necyc lope ntadienyl complexes,i. e., [Ru(η5-c5R5)(η6- are ne)]+ (1, R= H, arene = C6H6; 2, R = Me, arme = C6H6; 3, R = H, arctic = C6H3Me3; 4, R = Me, arene = C6H3Me3; 5, R = H, arene = C6Me6; 6, R = Me, arene = C6Me6) was studied by cyclic voltammetry. These compounds are capable of both oxidation and reduction. The reduction potential values depend on the number of methyl groups in the complex. Reduction of benzene complexes I and 2 by sodium amalgam in THF leads to the formation of decomplexation products, the addition of hydrogen to benzene, and dimerization of the benzene ligands. Both chemical and electrochemical reductions of mesitylene complexes3 and4 result in dimeric products [(η5-C5R5)Ru(μ-η5;η5-Me3H3C6H3Me3)Ru(η5-C5R5)] (14, R = H; 15, R = Me). The action of sodium amalgam on compound5 gives products of hydrogen addition to both hexamethylbenzene (17) and cyclopentadienyl (18) ligands along with the major product, the dimer [η5-C5H5)Ru(μ-η5; η5-Me6C6C6Me6)Ru(η5-C5H5)] (16). In contrast to5, its permcthylated analog 6 is only capable of adding hydrogen to the hexamethylbenzene ligand.
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  • 95
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    Russian chemical bulletin 45 (1996), S. 1952-1954 
    ISSN: 1573-9171
    Keywords: reactivity ; synthesis ; (N,N-difluoroamino)dinitroacetonitrile ; 5-[(N,N-difluoroamino)dinitromethylltetrazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract High reactivity of the nitrite group in (NN-difluoroamino)dinitroacetonitrile was demonstrated. Based on its reaction with HN3, a new preparative method for the synthesis of 5-[(N,N-difluoroamino)dinitromethylltetrazole was developed; some derivatives of the latter compound have been obtained.
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  • 96
    ISSN: 1573-9171
    Keywords: tetraphenylantimony hydrogen phthalate ; synthesis ; X-ray structural study ; molecular structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Tetraphenylantimony hydrogen phthalate, Ph4SbOC(O)C6H4000H-o, was prepared by the reaction of pentaphenylantimony with phthalic acid. According to the data of X-ray structural analysis, the resulting compound is a trigonal-bipyramidal complex of antimony with three phenyl groups in equatorial positions; the fourth phenyl group and the carboxyl fragment are in axial positions. The CSbO angle is 177.5(1)° the Sb-C(Ph)eq and Sb-C(Ph)ax distances are 2.099(4)-2.177(4) A and 2.129(4) A, respectively. The H atom of the free carboxyl group and the carbonyl O atom of another carboxylate group form an intramolecular hydrogen bond.
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  • 97
    ISSN: 1573-9171
    Keywords: trinuclear iron carboxylate complexes ; synthesis ; X-ray structural analysis ; spectroscopy ; cyclic voltammetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Reactions of iron(m) salts with a new bidentate ligand, which is potentially capable of forming binuclear iron complexes upon complexation, were studied. Under various conditions, we succeeded in isolating only the trinuclear cationic complex (FeIII 3(O2CR)6(μ3-)17+ (1), where RCO2 is 2-(pyrid-2-ylmethoxy)benzoic acid protonated at the pyridyl moiety. The structure of 1 was established by spectral, magnetic, and X-ray structural studies. Cyclic voltammetry in McCN in the temperature range from -35 to 20 °C demonstrated that 1 undergoes successive FeIII→FeII reduction in three one-electron stages, which is indicative of the electronic interaction between iron atoms in the complex.
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  • 98
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    Russian chemical bulletin 45 (1996), S. 2018-2019 
    ISSN: 1573-9171
    Keywords: trimethylarsine ; trimethylaluminum ; synthesis ; ecological safety
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A convenient, highly efficient, and environmentally safe procedure for the preparation of trimethylarsine was proposed. A quantitative yield of this compound in the reaction of As2O3 with AIMe3 was attained for the first time by using mechanochemical activation of the process.
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  • 99
    ISSN: 1573-9171
    Keywords: hydrosilanes ; amines ; N-siloxycarbonylation ; carbon dioxide ; O-silylurethanes ; synthesis ; hexamethyldisilazane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reaction of hydrosilanes with carbon dioxide and secondary amines or silylamines was studied for the first time. The dependence of the composition and the structure of the products obtained on the nature of the reagents and on the reaction conditions was found. The hydrosilane-carbon dioxide system, unknown previously, can be used as anN-siloxycarbonylating reagent in the synthesis ofO-silylurethanes. A scheme for the formation ofO-silylurethanes was proposed.
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  • 100
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    Russian chemical bulletin 45 (1996), S. 2196-2198 
    ISSN: 1573-9171
    Keywords: 4,4′-thiodiphenol ; diamide of phenylphosphonous acid ; crown ethers ; synthesis ; oligothioarylenecyclophosphonites ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new representative of phospho(scIII)crown ethers was obtained based on 4,4′-thiodiphenol and tetraethyldiamide of phenylphosphonous acid. Thiaphospho(III)crown ethers can be prepared by different methods depending on the ratio of the initial reactants and the reaction conditions. The structures of the compounds obtained were confirmed by spectroscopic data and X-ray structural analysis.
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