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  • Organic Chemistry  (3,492)
  • 1985 - 1989  (3,492)
  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 2
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relative rates of hydrogen atom abstraction from a series of twelve saturated cyclic ethers and sulfides were determined at 70°C. The abstracting radical could be generated from bromotrichloromethane both photolytically or by the thermal decomposition of AIBN. The reaction rates did not show a dependence upon method of radical generation. Reaction occurred only at the position adjacent to the heteroatom. The reactivity of the cyclic ethers was in the order C4H8O > C6H12O > C3H6O > C5H10O. This trend would indicate appreciable influence by ring strain, however, the slightly greater reactivity of tetrahydrofuran relative to oxepane suggests a contribution by stereoelectronic factors as well. The reactivity of the cyclic sulfides, which reacted faster than the corresponding ethers, was in the order C4H8S > C5H10S > C6H12S. This would imply little influence of ring strain. The major structural effect would be that of variable electron donating ability of the sulfur atom. The rate of reaction of thietane was also determined. It was found to preferentially undergo SH2 attack at the sulfur atom followed by ring opening rather than hydrogen abstraction. The reactivities of both series of compounds were decreased by the inductive effect of a second heteroatom beta to the reaciton site.
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  • 3
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rates of N-methylation of pyridine and its ring-substituted derivatives by trimethyl phosphate were measured in D2O and in CDCl3. Relative rates, together with the solvent activity coefficients of substrates for the transfer form chloroform to water, were used for determining the solvent activity coefficients of the activated complexes for this SN2 reaction. The results indicate early activated complexes for all pyridines, with the most nucleophilic substrate showing the most reactant-like activated complex.
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  • 4
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The hydrolysis reactions of N-(2,4,6-trinitrophenyl)piperidine (2) and N-(2,4,6-trinitrophenyl)-morpholine (3) were studied. Two kinetic processes well separated in time are observed in both reactions. The fastest process, which is reversible, leads to the formation of a species of λmax 260 and 410 nm and is attributed to the formation of a σ complex of stoichiometry 1 : 2 due to the addition of a second HO- to the σ complex of 1 : 1 stoichiometry. The slowest process leads quantitatively to picrate ion. The equilibrium constants for the formation of the σ complexes of 1:1 and 1:2 stoichiometries and the rate of formation and decomposition of the latter complex were determined. The kinetic data for the slow process lead to the conclusion that the picrate ion is formed from the attack of HO- on the two σ complexes, confirming previous findings. There are some differences in the calculated rates for 2 and 3 which may be an indication that the elimination of the amine is partially rate determining.
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  • 5
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The ups and downs, and reasons therein, of the π-complex theory of the mechanism of the benzidine rearrangements, and the possible role of π-complexes in a newer understanding of the rearrangements, are described.
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  • 6
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acid-catalysed condensation of resorcinol with aromatic aldehydes results in 2,8,14,20-tetrasubstitued calix[4] areneoctols. Sixteen compounds of this type containing different aromatic substituents were synthesized. The ring closure step, under the conditions of the reaction, is a reversible process. Four configurations are possible for every constitution, viz. cccc, cctt, ccct and ctct, but only cccc and cctt were formed in detectable amounts. In seven cases the thermodynamically more stable cccc isomers (1a-5a, 7a, 8a) and also the kinetically controlled cctt isomers (1b-5b, 7b, 8b) could be isolated. The configurations of the compounds were assigned by temperature-dependent 1H NMR analysis. The conformational motions of the macrocyclic ring permit only the cccc isomers to show coalescence for the signals of the aromatic Hb protons. The coalescence temperature was determined for isomers 1a (ΔG384≠ = 83·5 kJmol-1) and 3a (ΔG369≠ = 83·7 kJ mol-1). For steric reasons the ‘chair-chair’ conformers B and the ‘quasi-boat-chair’ conformers F are favoured. 1H and 13C NMR shifts show that compounds 1a-5a and 1b-5b have a quasi-axial arrangement of the aromatic substituents, whereas 6-9 have a quasi-equatorial arrangement of the substituents.
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  • 7
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The basic hydrolysis of 2,4-dinitrochlorobenzene (DNCB) and 2,4-dinitrofluorobenzene (DNFB) was studied in the presence of β-cyclodextrin (CDOH) and in the presence of hydroxy-functionalized micelles containing either a primary hydroxy group [hexadecyl-2-hydroxyethyldimethylammonium bromide (CHEDAB)] or a secondary hydroxy group [headecyl-2-hydroxypropyldimethylammonium bromide (CHPDAB) and 2-hydroxyhexadecyltrimethylammonium bromide (2-OHCTAB)].In all systems a biphasic reaction was observed. The first phase consisted of a competition between the additive (either micelle or cyclodextrin) and hydroxide ion for the aromatic substrate, and the second phase consisted of the hydrolysis of the trapped aryl micellar or cyclodextryl ether.The percentage of trapping of the aromatic substrate by the cyclodextrin was similar to that found for reactions in the hydroxy-functionalized micelles (CHPDAB and 2-OHCTAB) which contained secondary hydroxy groups. The relative rates of reaction for DNFB and for DNCB, i.e. F/Cl rate ratios, in the presence of CDOH were similar to those obtained in the presence of 2-OHCTAB but less than that obtained in the presence of CHEDAB. These results support the assumption that in CDOH the secondary hydroxy groups of C-2 or C-3 are involved in covalent bond formation with the aromatic substrate rather than the primary hydroxy group of C-6. All the reactions studied proceed much more slowly in the presence of CDOH than in the presence of the hydroxy-functionalized micelles. This may reflect a catalytic effect of the positively charged surface present in the micelles but not in the cyclodextrin.
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  • 8
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Using the solvatochromic indicator method, a scale of solvent hydrogen-bond basicity, β1 (General), has been set up using a series of double regression equations, \documentclass{article}\pagestyle{empty}\begin{document}$$ \nu = \nu _0 + s\pi _1^* + b\beta _1 $$\end{document} for 11 aniline-type indicators. A similar solvent scale, β1 (Special), has been constructed by the homomorphic comparison method using only results by Laurence et al. on the indicators 4-nitroaniline and 4-nitro-N,N-dimethylaniline. Results are available from our previous work on a general solute scale, β2H, and we have also obtained a special solute scale, β2 (pKHB) from available log K values for hydrogen-bond complexation of bases with 4-fluorophenol in CCl4. However, the two solute β2 scales are virtually identical.It is shown that there is a general connection between β1(General) and β2H, with r = 0·9775 and s.d. = 0·05 for 32 compounds, and between β1(Special) and β2H, with r = 0·9776 and s.d. = 0·06 for the same 32 compounds. The latter correlation over 60 compounds yields r = 0·9684 and s.d. = 0·07. However, there are so many compounds in these regressions for which the differences in the solvent and solute β values are larger than the total expected error of 0·07 units that the use of β1 to predict β2 or vice versa is a very hazardous procedure. About 70 new β1 values obtained by the double regression method are also reported.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 10
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Reaction products of bifunctional chain molecules with structure X—(CH2)n—Y may critically depend on the chain length n. When the chain length is short (n ≤ 5), reaction products particular to an intramolecular reaction can be dominant, while a process corresponding to an intermolecular reaction between X—CH3 and H3C—Y may take place for higher homologues having large n (≥10). The reaction switching dependent on n is explained in terms of the encounter probability for both end groups (X and Y) with conformations pertinent to product formation. The reaction switching of this sort is discussed on the basis of a reactivity profile recorded as a function of the chain length. Similar reactivity profiles have been observed for thermal Friedel-Crafts cyclization and photo-Smiles rearrangement/photoredox reaction. It is anticipated that the magic methylene chain length of 7 may give rise to an appreciable decrease in reaction yields (e.g. ‘difficulty in medium-sized ring closure’) or an anomalous switching of reaction pathways due to chain length effects.
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  • 11
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 205-213 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mechanism of the Grignard reactions of aromatic ketones in THF was studied by spectroscopic and kinetic methods. The stable radical intermediates generated in the initial electron transfer from Grignard reagent to ketones are in a state of aggregated dimer of corresponding ion-radical pairs; in which two ketone anion radicals are bridged by a dimer di-cation of Grignard reagent. Subsequent alkyl radical transfer from dimeric Grignard reagent cation moiety to ketone anion radical aggregated each other are promoted by a participation of another neutral Grignard reagent. Proposed mechanism by present authors is able to explain well addition products/reduction products ratios in the Grignard reactions.
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  • 12
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solvolysis of 21 different 3- or 17-androstanyl tosylates or chlorides with halogen, hydroxy or oxo substituents in 17- or 3-position shows rate constant variations in hexafluoro isopropanol of up to 6·3 with regular differences for epimeric substituents. Similar variations ae seen over a distance of ∼10 Å in 13C-NMR shifts at C-17-ones of androstan-17-ones with varied halogen substituents in C-3, whereas the shielding observed at other distant carbon atoms excludes significant through bond effects. It is shown how, on the basis of suitable Coulomb-type equations and of force field minimized geometries, both the stability variation of carbocationic transition states and the carbonyl group polarization are predictable by linear electric field effects, using the same parametrization.
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  • 13
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The gas-phase pyrazole elimination of N-alkyl pyrazoles has been studied using MNDO semi-empirical molecular orbital (MO) theory with complete geometry optimization of all stationary points. We found that the activation energies (Ea) of the concerted processes are around 80 kcal/mol, 25 Kcal/mol higher than experimental values. But the differences in Ea between compounds with different substituents are in good agreement with the experimental ones.
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  • 14
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystal and molecular structures of dimesitylketene (1) and bis(3,5-dibromo-2,4,6-trimethylphenyl)ketene (2), the first free ketenes to be studied by X-ray diffraction, have been determined. The molecules of 1 and 2 have crystallographic C1 and C2 symmetry, respectively, and exist in a propeller conformation. Molecular mechanics calculations of 1 and 2 using a modification of Allinger's new allene parameters reproduce satisfactorily the structural parameters of the ketenes. The torsional angles of the aryl rings in 1 and 2 are similar (ca. 50°) and are regarded as ‘intrinsic’ values for a 1,1-dimesitylvinyl propeller. From the similarity in aryl torsional angles in 1 and 2 it is concluded that the buttressing effects in 2 (if any) are not markedly manifested in the structural parameters of 2.
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 7-9 
    ISSN: 0899-0042
    Keywords: substrate enantioselectivity ; product enantioselectivity ; Michaelis-Menten analysis ; intrinsic activity ; potency ; receptor affinity ; efficacy ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 57-62 
    ISSN: 0899-0042
    Keywords: chiral stationary phase ; α-amino phosphonate ; chromatographic separation of enantiomers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A chiral statonary phase (CSP) derived from an N-(3,5-dinitrobenzoyl)-α-aminobenzylphosphonate has been prepared and evaluated for its utility in the direct separation of enantiomers. This CSP, 2, is structurally related to earlier N-(3,5-dinitrobenzoyl)-α-acids acid-derived phases (e.g., CSP 1), but the mode of attachment to the support is different. In scope; CSP 2 is qualitaively similar to CSP 1. However, it differs quantitatively from CSP 1, showing either greater or lesser selectivity for different pairs of enantiomers.
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  • 17
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    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 121-126 
    ISSN: 0899-0042
    Keywords: stereoselective metabolism ; sulfate conjugation ; in vitro sulfation ; sympathomimetic amines ; chiral separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Little is known about the stereochemistry of sulfation of chiral phenolic drugs. In this study we examined several in vitro approaches to this question, using (+)-, (-)-, or (±)-terbutaline as the substrate and the rat liver cytosol as the phenolsulfotransferase enzyme source. The cosubstrate PAPS was either generated by the cytosol from inorganic sulfate and ATP or added to the cytosol. The intact sulfate conjugates formed were determined by HPLC. Using the PAPS generating system, which is best suited for the production of relatively large quantities of sulfate conjugates, with the individual enantiomers as substrates, (+)-terbutaline was conjugated to a much greater extent than (-)-terbutaline; the (+)/(-)-enantiomer ratio was 7.3 ± 0.3 (mean ± SE). When (±)-terbutaline was the substrate and chiral derivatization was employed to separate the sulfate enantiomers formed, a similar (+)/(-)-enantiomer ratio of 7.9 ± 0.2 was obtained. With PAP35S added to the cytosol, an approach best suited for kinetic studies, the substrate concentration dependence of sulfation could be determined. The Km app for this reaction was identical for (+)- and (-)-terbutaline. However, the Vmax app was 8.1 ± 0.4 times greater for (+)-terbutaline. This study for the first time shows enantioselectivity in sulfation of a chiral phenolic drug. The experimental approaches used should be valuable for human studies of stereoselectiven sulfation of terbutaline and other chiral drugs.
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  • 18
    ISSN: 0899-0042
    Keywords: enantioselective epoxidation ; cytochrome P-450-dependent monooxygenases ; species dependence of microsomal epoxidation ; product enantioselectivity ; substrate enantioselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantioselectivity of the in vitro conversion of simple prochiral and chiral aliphatic alkenes into oxiranes by liver microsomes of untreated or induced (phenobarbital) rats, of untreated or induced (phenobarbital, benzo[α] pyrene) mice, and of humans was determined by complexation gas chromatography. The enantiomeric excess (ee) of the epoxides extends from 0 (trimethyloxirane) to 50% (ethyloxirane). The configuration (R or S) of the enantiomers formed in excess is consistent for homologous oxiranes but is species dependent and in some cases influenced by enzyme induction. Enantioselectivity differences of aliphatic alkene epoxidation by human liver microsomes of four individuals are negligible.
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  • 19
    ISSN: 0899-0042
    Keywords: resolution by crystallization ; racemic mixture ; dansyl-D-leucine ; dansyl-L-leucine ; dansyl-D-norleucine ; dansyl-L-norleucine ; dansyl-D-phenylalanine ; dansyl-L-phenylalanine ; β-cyclodextrin ; γ-cyclodextrin ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optical enrichment from racemic dansyl-leucine, dansyl-norleucine, and dansyl-phenylalanine with both β- and γ-cyclodextrins in water is reported. Initial crystallization yielded the dansyl-L-leucine isomer complexed in excess with β-cyclodextrin with an optical purity of 62-78% depending on experimental conditions. The optical purities obtained for L-norleucine and L-phenylalanine were 71 and 64%, respectively. The optical purity can be increased with continued recrystallization. The dansyl-D-leucine isomer was obtained in the mother liquor with an optical purity of 54-93% depending on experimental conditions. The optical purities obtained for D-norleucine and D-phenylalanine were 72 and 58%. The optical purity of the isomer depended on the molar ratio of host:guest and the pH value of the solution. Optimum enrichment of both enantiomers was achieved with host:guest ratios of 2 : 1 and 3 : 1. Although maximum crystalline yield of the dansyl-leucine/CD inclusion complex was obtained at a pH of 3.5, optical purity of both enantiomers was less than that obtained at other pHs. The influence of the molar ratio of host:guest and the pH value of the solution are discussed. This method is suitable for large-scale enantiomeric separations.
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  • 20
    ISSN: 0899-0042
    Keywords: enantiomeric separations ; chiral stationary phase ; Pirkle-type phases ; HPLC ; anthelmintics ; benzimidazole sulfoxides ; albendazole ; fenbendazole ; oxfendazole ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The direct enantiomeric resolution of albendazole sulfoxide (SOABZ), an anthelmintic drug belonging to the benzimidazole class, is reported on a chiral stationary phase (CSP) synthesized by covalent binding of (S)-N-(3,5-dinitrobenzoyl)tyrosine-O-(2-propen-1-yl) methyl ester on a γ-mercaptopropylsilanized silica gel. A comparison with the resolution achieved on commercially available Pirkle-type CSPs obtained from N-(3,5-dinitrobenzoyl) derivatives of (R)-phenyglycine or (S)-phenylalanine is described. Some structurally related chiral sulfoxides including oxfendazole (SOFBZ) are also studied. Optimization of the mobile phase nature and composition is investigated showing that a hexane-dioxane-ethanol ternary mixture affords an almost baseline resolution (Rs = 1.25); however, in this case, albendazole sulfone (SO2ABZ) is eluted between the two sulfoxide enantiomers; accordingly, a hexane-ethanol mobile phase would be preferred for biological samples containing both metabolites. The influence of temperature on the resolution is depicted with a hexane-ethanol mobile phase. Finally, application to the enantiomeric assays of SOABZ in plasmatic extracts of rat, sheep, bovin, and man after oral administration of albendazole (sulfoxidized to SOABZ and SO2ABZ) is reported. Some distortions in the enantiomeric ratios are evidenced depending on the species.
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  • 21
    ISSN: 0899-0042
    Keywords: enantiomers ; chiral discrimination ; drugs ; hydrophobic interaction ; biopolymers ; elution order ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optical resolution on the analytical scale of a number of racemic pharmaceuticals and some other biologically active compounds has been studied using immobilized bovine serum albumin (BSA) as the stationary phase. For some of the compounds the elution order was determined by the use of optically enriched fractions obtained from a preceding passage of a sample through a preparative column containing microcrystalline triacetylcellulose (MCTA). The reversal in the sign of optical rotation shown in the polarimetric elution profile from the latter, combined with the integrated peak area ratio obtained on resolution on the analytical column, gave directly the order of elution. For one of the benzothiadiazines studied (bendroflumethiazide), increasing the pH of the mobile phase produced opposite effects on the retention of the two enantiomers, leading to a large effect on the separation factor. For many of the compounds studied, high separation factors (α > 2) could be achieved.
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  • 22
    ISSN: 0899-0042
    Keywords: chromatography ; chirality ; chiral recognition ; β-aminoalcohols ; stereochemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three chiral stationary phases, obtained by derivatizing γ-mercaptopropylsilanized silica gel with quinine, quinidine, and cinchonidine, have been employed in the resolution of N-acyl derivatives of β-hydroxyphenethylamines. The use of circular dichroism for detection and NMR analysis of analyte-selector mixtures provides an experimental basis for preliminary assignment of a recognition mechanism.
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  • 23
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    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 167-169 
    ISSN: 0899-0042
    Keywords: enantioselectivity ; three-point model ; chiral receptors ; chiral separations ; didactic model ; elusion of the three-point model ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hands can be used to demonstrate the three-point model of chiral recognition. The points of attachment are thumb, forefinger, and middle finger. This vivid model has the advantages of simplicity, perspicuity, and availability at any time, although two persons are necessary. It can be shown that two interactions are not sufficient for chiral recognition but that three attractive or two attractive and one repulsive attraction are needed. It can also be used to explain some possibilities of weakening or elusion of the three-point model.
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  • 24
    ISSN: 0899-0042
    Keywords: phenglutarimide enantiomers ; enantioselectivity ; antiparkinsonian drugs ; M1-selective antagonists ; rabbit vas deferens ; pirenzepine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The affinity of the enantiomers of phenglutarimide at three muscarinic receptor subtypes was examined in vitro using field-stimulated rabbit vas deferens (M1 receptors) and guinea pig atria (M2α receptors) and ileum (M2β receptors). Extremely high stereoselectivity was observed and higher affinities (up to 6000-fold) were found for the (+)-S-enantiomer. The stereoselectivity ratios were different at the three subtypes, and the stereochemical demands made by the muscarinic receptors were most stringent at M1 receptors. (+)-(S)-Phenglutarimide was found to be a potent M1-selective antagonist (pA2 at M1 = 8.53). Its receptor selectivity profile is qualitatively similar to that of pirenzepine. (-)-(R)-Phenglutarimide showed no comparable discriminatory properties.
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  • 25
    ISSN: 0899-0042
    Keywords: pharmacokinetics ; terbutaline ; enantiomers ; human ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Terbutaline is a β2-agonist and administered as the racemic mixture. The pharmacokinetics of the separate enantiomers differ with respect to degree of absorption and clearance. In the present study, repeated doses of racemic terbutaline were given to six healthy volunteers. Plasma was analyzed for the concentrations of the two enantiomers. The observed plasma concentrations at steady state differed from those predicted from the values observed after single dose administration of the separate enantiomers. The difference between the observed and predicted values can be tentatively explained by a combined influence of (-)-terbutaline on the absorption of (+)-terbutaline and the influence of (+)-terbutaline on the elimination of (-)-terbutaline. The results have implications for the interpretation of effect/concentration studies with terbutaline, but do not affect the doses used in clinical practice.
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  • 26
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    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 178-179 
    ISSN: 0899-0042
    Keywords: CD spectra ; optical rotation ; phthalideisoquinoline base and salts ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The appearance of positive charge on the nitrogen moiety of phthalideisoquinoline alkaloids brings about a strong change in the intensities of CD Cotton effects. Hence the optical rotations of enantiomeric salts and their parent base of identical configuration are often of opposite sign. Thus, the name (+)-bicuculline-methiodide for the methiodide salt of (+)-bicuculline is false.
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  • 27
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989) 
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 28
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 178-179 
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 29
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 183-191 
    ISSN: 0899-0042
    Keywords: enantiomorphism ; dissymmetry ; chirality ; enantioselectivity ; diastereoselectivity ; steric complementarity ; asymmetric induction ; three-point contact ; circularly polarized radiation ; circular dichroism ; parity nonconservation ; electroweak interaction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pasteur's conjecture (1860) that biomolecular homochirality arose from a chiral natural force as yet inaccessible in the laboratory was supplanted by Fischer's (1894) “key and lock” hypothesis of stereoselection in enantiomer to diastereomer conversions, whether in the laboratory or in living organisms. Elaborations of the “key and lock” hypothesis by Haldane (1930) and Pauling (1948) have been illustrated and supported with modification by X-ray diffraction crystal structures of enzyme-substrate complexes over the past quarter century.Two types of mechanism for the product diastereoselectivity in the reactions of an enantiomer with an achiral reagent, early proposed, have recent support: one proposes a quasidiastereomeric structure for the enantiomer attacked in the ground state, the other for the corresponding transition state of the reaction. Approaches to the differential biological activity of two enantiomers postulate either the complete binding of each isomer to a chiral receptor site, resulting in diastereomeric complexes with inequivalent bioactivities, or the differential binding of the two isomers to a set of three sites, with which only one isomer is sterically congruent.Biochemical homochirality, based on the chiral stereoselectivity of both biosynthetic and metabolic reactions, derives from the evolutionary pressure for a progressive enhancement of the kinetic efficiency and economy of those reactions. Recently Pasteur has been vindicated in part, and the problem of the original prebiotic enantiomeric excess left outstanding by Fischer has been solved. The unification of the electromagnetic with the weak interaction provided a universal chiral natural force, the electroweak interaction, which favours the chiral series selected during the course of biochemical evolution, both the D-sugars and the L-amino acids.
    Additional Material: 4 Ill.
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  • 30
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 192-196 
    ISSN: 0899-0042
    Keywords: propranolol enantiomers ; enantiomers ; propranolol ; β-receptor-blocking drugs ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Only limited information is available on the stereochemistry of the in vivo distribution of β-receptor-blocking drugs. In this study we determined the levels of the propranolol enantiomers in plasma, cerebrospinal fluid (CSF) and central nervous system (CNS), and peripheral tissues in the dog following an intravenous dose of a deuterium-labeled pseudoracemate. The appearance of the propranolol enantiomers in the CSF was rapid and nonstereoselective, with maximum concentrations reached at 15 min after dosing. The levels of the enantiomers in both CSF and plasma then declined in a parallel biphasic fashion, with a terminal t1/2 of about 125 min. Except for an early high CSF/plasma concentration ratio of 0.35, the CSF propranolol levels corresponded to the unbound concentration in plasma, CSF/plasma 0.20. All areas of the brain showed a similar uptake of propranolol, with a tissue concentration exceeding that in plasma about 10-fold during the terminal phase of elimination. The uptake of propranolol by peripheral tissues varied widely, ranging from a 50-fold accumulation by the lungs compared to plasma to no accumulation by adipose tissue. However, as for the CSF, there was no evidence of stereoselective uptake of propranolol by any CNS or peripheral tissue except for the liver. A significantly higher level of (+)- vs. (-)-propranolol in liver tissue presumably was a reflection of stereoselective hepatic metabolism of (-)-propranolol by this tissue. The slight stereoselectivity in plasma binding of propranolol known to exist in the dog had no significant influence on tissue or CSF distribution.
    Additional Material: 2 Ill.
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  • 31
    ISSN: 0899-0042
    Keywords: fenofibrate ; chiral reduction ; species differences ; prochiral to chiral transformation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The prochiral carbonyl group of fenofibrate (isopropyl 2-[4-(4-chlorobenzoyl)phenoxy]-2-methyl propionate) is reduced during its metabolism giving rise to a chiral secondary alcohol, “reduced fenofibric acid.” Chiral and diastereomeric HPLC methods have been developed for the determination of its enantiomeric composition and these have been applied to the measurement of the “reduced fenofibric acid” enantiomers in urine of rats, guinea pigs, dogs, and human volunteers given [14C]fenofibrate. In the three animal species, the reduction is markedly enantioselective for the (-)-isomer, the enantiomeric ratios (-/ +) being 95:5. This was not due to differences in the excretion of the enantiomers, since when racemic “reduced fenofibric acid” was given to rats it was recovered in the urine with the same enantiomeric composition as the dose form. In humans the ratio was 52:48 showing the lack of stereoselectivity of reduction in this species.
    Additional Material: 2 Ill.
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  • 32
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 202-208 
    ISSN: 0899-0042
    Keywords: opioid ligand ; 4-arylpiperidines ; conformation, NMR ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and stereochemistry (configuration and preferred solute conformation) of some 4-alkyl (methyl, n-propyl, isobutyl)-4-(3-hydrxyphenyl)-1-methylpiperidines and corresponding 3-methyl diastereoisomeric pairs are reported, together with their in vivo and in vitro activities as opioid ligands. All potent agonists exhibit a preference for axial 4-aryl chair conformations when protonated, and stereochemical analogies with rigid opioids of the benzomorphan class are discussed. Antagonist properties are found in compounds with preference for equatorial 4-aryl chairs, notably the cis 3,4-dimethyl derivative.
    Additional Material: 3 Tab.
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  • 33
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 209-215 
    ISSN: 0899-0042
    Keywords: enantiomeric separation ; bioanalysis ; α1-acid glycoprotein column ; disposition (R)- and (S)-atenolol ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for the determination of (R)- and (S)-atenolol in human plasma and urine is described. The enantiomers of atenolol are extracted into dichloromethane containing 3% heptafluorobutanol followed by acetylation with acetic anhydride at 60°C for 2 h. The acetylated enantiomers were separated on a chiral α1-AGP column. Quantitation was performed using fluorescence detection. A phosphate buffer pH 7.1 (0.01 M phosphate) containing 0.25% (v/v) acetonitrile was used as mobile phase. The described procedure allows the detection of less than 6 ng of each enantiomer in 1 ml plasma. The relative standard deviation is 4.4% at 30 ng/ml of each enantiomer in plasma. The plasma concentration of (R)- and (S)- atenolol did not differ significantly in two subjects who received a single tablet of racemic atenolol. The R/S ratio of atenolol in urine was ∼ 1.
    Additional Material: 7 Ill.
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  • 34
    ISSN: 0170-2041
    Keywords: Pyrano[2,3-c]pyrazoles ; Pyrano[2,3-b]pyridines ; Pyrano[2,3-d]pyrimidine ; 1,8-Diazanaphthalenes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethyl 6-amino-5-cyano-4-aryl-2-methyl-4H-pyran-3-carboxylates 4 could be converted into 1,6-diazanaphthalene, pyrano-[2,3-c]pyrazole, isoxazolo[3,4-b]pyridine, pyrano[2,3-b]pyridine, 1,8-diazanaphthalene, and pyrano[2,3-d]pyridine derivatives on treatment with malononitrile, hydrazine hydrate, hydroxylamine hydrochloride, (arylmethylene)malononitrile, cyanoacetamide, and acetic anhydride, respectively.
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  • 35
    ISSN: 0170-2041
    Keywords: 1H-Pyrazoles ; Benzoin phenylhydrazone ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyrazoles by Cyclisation of Benzoin Phenylhydrazone with AldehydesBy fusing (E)- or (Z)-benzoin phenylhydrazone and aldehydes, 3-substituted 1H-pyrazoles (2) are obtained. The structure of 2d was confirmed by X-ray analysis.
    Additional Material: 1 Ill.
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  • 36
    ISSN: 0170-2041
    Keywords: Pyrido[2,1-d][1,5]benzothiazepines ; Pyrido[2,1-d][1,5]benzoxazepines ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies on the Chemistry of O,N- and S,N-Containing Heterocycles, 91). - Investigations of the Formation of Pyrido[2,1-d]-[1,5]benzoxazepines and Pyrido[2,1-d][1,5]benzothiazepinesThe formation of the pyrido-anellated heterocycles 1 and 3 has been studied. GC-MS investigations of the reaction of 2-aminophenol and 7 with acetone show the stepwise condensation of acetone units. Furthermore, the reaction of 7 with 2-buta-none, benzaldehyde, and acetophenone, respectively, has been examined.
    Additional Material: 3 Tab.
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  • 37
    ISSN: 0170-2041
    Keywords: Electron/proton transfer ; Photoaddition ; 2(1H)-Pyrimidinone ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Photochemische Reaktionen von 1-Alkyl-4,6-diaryl-2(1H)-pyrimidinonen in Gegenwart von AminenBei Bestrahlung der 1-Alkyl-4,6-diaryl-2(1H)-pyrmidinone 1 unter Zusatz von aliphatischen Aminen wurden die C—C-gebundenen 1:1-Addukte und/oder die reduzierten Dihydropyrimidinone erhalten, wogegen 1 unter Zusatz von aromatischen Aminen ausschließlich die 1:1-Addukte ergab. Die Photoadditionen Aminen an 1 können durch einen stufenweisen Elektronen/Protonen-Übertragungsmechanismus erklärt werden.
    Notes: Irradiation of 1-alkyl-4,6-diaryl-2(1H)-pyrimidinones 1 in the presence of aliphatic amines gave the C—C-bonded 1:1 adducts and/or the reduced dihydropyrimidinones, while irradiation of 1 in the presence of aromatic amines gave the 1:1 adducts exclusively. The photoadditions of amines to 1 can be explained by a sequential electron/proton transfer mechanism.
    Additional Material: 1 Tab.
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  • 38
    ISSN: 0170-2041
    Keywords: Paraconic acid ; Lipase ; Asymmetric hydrolysis ; Prochiral diacetates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Präparative Bioorganische Chemie, XI. - Darstellung der Enantiomeren von Paraconsäure durch Lipase-katalysierte asymmetrische Hydrolyse von prochiralen Diacetaten als SchlüsselschrittEs wird die Darstellung von (S)-(-)-Paraconsäure (1) aus [2-(Acetoxymethyl)-3-phenylpropyl]acetat (4) durch dessen asymmetrische Hydrolyse mit Schweine-Pankreas-Lipase als Schlüsselreaktion beschrieben. Ähnlich erhält man (R)-(+)-1 aus [2-(Acetoxymethyl)-4-pentenyl]acetat (2) durch dessen Hydrolyse mit Lipase MY.
    Notes: (S)-(-)-Paraconic acid (1) was prepared from 2-(acetoxymethyl)-3-phenylpropyl acetate (4) by its asymmetric hydrolysis with pig pancreatic lipase as the key step. Similarly, (R)-(+)-1 was prepared from 2-(acetoxymethyl)-4-pentenyl acetate (2) by its asymmetric hydrolysis with lipase MY.
    Additional Material: 2 Tab.
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  • 39
    ISSN: 0170-2041
    Keywords: 2-Indolones, 3-(dicyanomethylene)- and 3-[cyano(ethoxycarbonyl)methylene]- ; AM 1 calculations ; INDO/S-CI calculations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Syntheses with Nitriles, LXXXIV. - Colour and Stereochemistry of 3-(Cyanomethylene)-2-indolones3-(Dicyanomethylene)-2-indolones (1a-c) and 3-[cyano(ethoxycarbonyl)methylene]-2-indolones (2a, b) are intensively red compounds, the chromophoric properties and stereochemistry of which are investigated. 1H- and 13C-NMR data show not only the existence of E,Z isomers in 2a, b but also trans-s-cis und trans-s-trans conformers of the E isomers (measurement of the difference NOE effect). This is proved by quantum chemical calculations (semiempirical AM 1 method). The INDO/S-CI method is applied to calculate the electronic excitation energies of 1a, b and 2a, b. Chromophoric properties are discussed to be intramolecular charge transfer transitions.
    Notes: 3-(Dicyanmethylen)-2-indolone (1a-c) und 3-[Cyan(ethoxycarbonyl)methylen]-2-indolone (2a-b) sind auffallend tiefrote Verbindungen. Die Farbigkeit und die Stereochemie dieser Stoffklasse werden untersucht. 1H- und 13C-NMR-Daten ergaben das Vorliegen von E,Z-Isomeren in 2a, b, wobei durch Messung des Differenz-NOE-Effektes das Auftreten von trans-s-cis- und trans-s-trans-Konformeren nachgewiesen werden kann. Quantenchemische Berechnungen mittels des semiempirischen AM1-Verfahrens unterstützen diese spektroskopischen Aussagen. Mit dem INDO/S-CI-Verfahren werden die elektronischen Anregungsenergien von 1a, b und 2a, b berechnet und die chromophoren Eigenschaften als intramolekularer Charge-Transfer-Übergang diskutiert.
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  • 40
    ISSN: 0170-2041
    Keywords: β-Lumicolchicine, oxidation with active manganese dioxide, oxidation with m-chloroperbenzoic acid ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Struktur zweier Oxidationsprodukte des β-Lumicolchicins: Eine ungewöhnliche Reaktion mit aktivem MangandioxidZwei ungewöhnliche Reaktionsweisen von MnO2 und m-Chlor-perbenzoesäure mit der tetrasubstituierten C=C-Bindung von β-Lumicolchicin (1-β) werden beschrieben. Aktiver Braunstein oxidiert die 7a,10b-Cyclobutendoppelbindung, wobei in 10b-Position eine Hydroxygruppe eingeführt und am C-Atom 7a unter Einbeziehung der Acetamido-Seitenkette ein 2-Oxazolinring geschlossen wird (2). Mit m-Chlorperbenzoesäure ergibt 1-β kein Epoxid, sondern unter Öffnung des Vierrings ein 1:1-Addukt (3). Die Kristallstrukturanalyse von 2 läßt intermolekulare Wechsel-wirkungen zwischen den OH-Gruppen und den Stickstoffatomen erkennen. 13C-NMR-Spektroskopie mit Doppelquantenkohärenz (INADEQUATE-Pulsfolge) zeigt, daß 2 in Lösung die gleiche Struktur wie im Kristall besitzt und beweist die Struktur von 3. Außer den 13C-NMR-Signalen von 2 und 3 werden auch die der stereoisomeren Lumicolchicine 1-β und 1-γ zugeordnet. Ferner werden die 13C, 13C-Kopplungskonstanten für 2 und 3 ermittelt.
    Notes: Two unusual reaction types of MnO2 and of m-chloroperbenzoic acid with the tetrasubstituted C=C bond of β-lumicolchicine (1-β) are presented. Active MnO2 oxidizes the 7a,10b cyclobutene double bond by adding a hydroxy group to the position 10b while the acetamido side chain is used to close a 2-oxazoline ring in position 7a (2). m-Chloroperoxybenzoic acid splits the cyclobutene ring of 1-β and forms a ketonic 1:1 adduct (3) instead of an epoxide. X-ray structure analysis of 2 reveals intermolecular interaction between the hydroxy groups and the nitrogen atoms. 2D-INADEQUATE 13C-NMR spectroscopy establishes structure 2 in solution, proves the structure of 3, and allows also to assign the 13C-NMR signals of the tetracyclic skeleton of the stereoisomeric lumicolchicines 1-β and 1-γ. Furthermore, 13C,13C coupling constants were determined for 2 and 3.
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  • 41
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989) 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 42
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 1-3 
    ISSN: 0170-2041
    Keywords: Isoquino[1,2-a][2]benzazepines, conformation of ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Isoquino[1,2-a][2]benzazepines, IV1). - Conformation of Isoquino[1,2-a][2]benzazepinesBy treatment with mercury(II) acetate, the hexahydroisoquino[1,2-a][2]benzazepines 1 afford the aromatic isoquinolinium salts 4. On the basis of the mechanism of this reaction and of 1H NMR spectroscopic studies the cis-conformation of the ring system of 1 is very likely.
    Notes: Die Hexahydroisochino[1,2-a][2]benzazepine 1 liefern bei der Umsetzung mit Quecksilber(II)-acetat die aromatischen Isochinolinium-Salze 4. Aufgrund des Mechanismus dieser Reaktion sowie 1H-NMR-spektroskopischer Untersuchungen konnte für 1 die cis-Konformation des Ringgerüstes wahrscheinlich gemacht werden.
    Additional Material: 2 Tab.
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  • 43
    ISSN: 0170-2041
    Keywords: Juvenoids ; Epoxidation, enantioselective ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Insekten-Wachstumsregulatoren, 241). - Synthese von optisch aktiven, verzweigten JuvenoidenAusgehend von Geraniol (3) wird die Synthese der beiden Enantiomeren der verzweigten Juvenoide 1a, b beschrieben. Die Racemat-Trennung des Alkohols 4a gelang durch enantioselektive Epoxidation nach Sharpless.
    Notes: Starting from geraniol (3), the synthesis of both enantiomers of the branched juvenoids 1a,b is described. Resolution of the racemic mixture of alcohol 4a was performed by Sharpless enantioselective epoxidation.
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  • 44
    ISSN: 0170-2041
    Keywords: Acetalization, stereoselective ; endo-Brevicomin, enantiomers ; exo-Brevicomin, enantiomers ; Frontalin, enantiomers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Stereoselective Acetalization of 1,1- and 1,2-Disubstituted Diols as Common Principle in the Synthesis of the Enantiomers of the Bicyclic Acetal Pheromones endo- and exo-Brevicomin and FrontalinThe acetalization of the 1,1- and 1,2-disubstituted diols 14-19 with the keto compounds 20 and 21 has been investigated. The substitution pattern of the used diols shows great influence on the stereochemistry of the obtained dioxolanes 22-27 (mixtures of diastereomers), while diastereoselectivity is determined by the reaction temperature (up to de ≧ 99%). Considering these investigations, the synthesis of the enantiomers of the pheromones endo- and exo-brevicomin (1 resp. 2) and frontalin (3) is described.
    Notes: Die Acetalisierung der 1,1- und 1,2-disubstituierten Diole 14-19 mit den Ketobausteinen 20 und 21 wird untersucht. Großen Einfluß auf die Stereochemie der gebildeten Dioxolane 22-27 (Diastereomerengemische) hat das Substitutionsmuster der eingesetzten Diole, wobei die Diastereoselektivität durch die Reaktionstemperatur determiniert wird (bis zu de ≧ 99%). Basierend auf diesen Untersuchungen wird die Synthese der Enantiomeren der Pheromone endo- und exo-Brevicomin (1 bzw. 2) sowie Frontalin (3) beschrieben.
    Additional Material: 8 Ill.
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  • 45
    ISSN: 0170-2041
    Keywords: Purines, condensed ; Pyrimido[2,1-f]purines ; Theophylline, derivatives ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compounds 2a-d and 4a-d are the sole products of the reaction between 8-aminotheophylline (1) or 8-(benzylamino)theophylline (3) and methyl acrylate, crotonate, methacrylate, and cinnamate in the presence of basic catalysts (Triton B or KOH). The structures of the compounds were determined by elemental analysis, spectral data, chemical transformations, and synthesis.
    Additional Material: 3 Tab.
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  • 46
    ISSN: 0170-2041
    Keywords: Phthalazines ; Thieno[3,4-d]pyridazines ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethyl 1-aryl-5-cyano-1,6-dihydro-4-methyl-6-oxo-3-pyridazinecarboxylates 1 react with elemental sulphur in ethanolic basic solutions to yield thieno[3.4-d]pyridazines 2. Compounds 2 readily react with electron-deficient olefins to yield phthalazines.
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  • 47
    ISSN: 0170-2041
    Keywords: Aspergillus niger ; 4,5-Dihydroisoxazole ; Yeast ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics and the stereoselectivity of the reduction by baker′s yeast of racemic 5-acetyl-4,5-dihydro-3-phenylisoxazole 1 to the corresponding alcohol in 2-propanol/water mixtures are strongly dependent from the 2-propanol/water ratio; at a ratio of 4.0, the reduction allows a kinetic resolution leading to alcohol 2 and ketone (R)-1 Subsequent reduction of (R)-1 with yeast in water and with Aspergillus niger leads to alcohols 3 and 4 with high ee.
    Additional Material: 2 Ill.
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  • 48
    ISSN: 0170-2041
    Keywords: Epoxidation ; Pheromone, chiral ; cis-Pityol ; Sulcatol ; Vanadyl acetylacetonate ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pure cis-(2R,5R)-pityol (1) was synthesized from ethyl (R)-3-hydroxybutanoate (3) via cyclization of (R)-sulcatol (2) with tert-butyl hydroperoxide in the presence of a vanadium catalyst. In the same manner, cis-(2S,5S)-pityol (1) was synthesized from (S)-3 via (S)-2.
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  • 49
    ISSN: 0170-2041
    Keywords: Mitsunobu inversion ; Pheromone, enantiomerically pure ; Sitophilate ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of sitophilate [(2S,3R-1] was achieved starting from (S)-2. Mitsunobu inversion of 7 to give crystalline 3,5-dinitrobenzoate 8 was the key step to diastereomerically pure 1. The antipode of the pheromone was also synthesized.
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  • 50
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 677-686 
    ISSN: 0170-2041
    Keywords: Iron carbonyl complexes ; (+)-Taxodion ; Terpenes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of (+)-TaxodioneA stereoselective synthesis of (+)-taxodione (1) starting from (-)-abietic acid (2) via the ironcarbonyl complex 4 is described. Conversion of the carboxyl function of 4 into a methyl group via 5 and 6 proceeds in excellent overall yield. The next steps are the introduction of oxygen functions in the positions 12 and 6. Oxidation with BSA yields the quinonemethide 1. The 1H- and 13C-NMR resonances of all compounds have been assigned.
    Notes: Eine stereoselektive Synthese von (+)-Taxodion (1) aus (-)-Abictinsäure (2) über den Eisencarbonyl-Komplex 4 wird beschrieben. Die Überführung der Carboxyl-Funktion von 4 in eine Methyl-Gruppe ist über 5 und 6 in sehr guter Gesamtausbeute möglich. Anschließend werden Sauerstoff-Substituenten gezielt in die Positionen 12 und 6 eingeführt. Mit BSA wird im letzten Schritt zum Chinonmethid 1 oxidiert. Die 1H- und 13C-NMR-Resonanzen aller Verbindungen sind eindeutig zugeordnet worden.
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  • 51
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 687-688 
    ISSN: 0170-2041
    Keywords: Indeno[1,2-b]furan-2,4(3H)-dione derivative ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-(Methoxycarbonyl)-4-(3-methoxyphenyl)-4-(trifluoromethyl)-4-butanolide (4) was synthesised from 3-methoxyphenyl trifluoromethyl ketone (1). Hydrolysis of the lactone ester 4, followed by treatment with polyphosphoric acid, led to an intermediate lactone acid 3, which on heating with PCl5 gave the indeno-[1,2-b]furandione 5.
    Additional Material: 1 Tab.
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  • 52
    ISSN: 0170-2041
    Keywords: Methanoditetrazolo-[1,3,6,8]tetrazecine ; Hexamethylenetetramine ; Tetrazole, 5-(chloromethyl)- ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Methanoditetrazolo-[1,3,6,8]tetrazecine from 5-(Chloro-methyl)tetrazole and HexamethylenetetramineIn contrast to N-substituted 5-(chloromethyl)tetrazoles (1; R=alkyl, aryl), the parent compound 1 (R=H) reacts with hexamethylenetetramine to give the methanoditetrazolo-[1,3,6,8]tetrazecine 4, a rather unusual system. This compound which is also produced on reaction of 7 with formaldehyde occurs in the (6RS,13RS) form.
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  • 53
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 691-693 
    ISSN: 0170-2041
    Keywords: (S)-Glycerol tosylate ; D-Ribono-γ-lactone ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Novel Synthesis of (S)-(+)-Glycerol TosylateEnantiomerically pure (S)-(+)-glycerol tosylate (3) was prepared from D-(+)-ribono-γ-lactone (4) in 43% overall yield.
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  • 54
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 695-697 
    ISSN: 0170-2041
    Keywords: (-)-Warburganal ; Insect antifeedant ; Sesquiterpene ; Enantioselective synthesis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantioselective total synthesis of (-)-warburganal (1) was achieved in 20 steps (8.1% overall yield) starting from (S)-3-hydroxy-2,2-dimethylcyclohexanone.
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  • 55
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 699-701 
    ISSN: 0170-2041
    Keywords: α-Methylanthraquinones ; Streptomycetes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An α-Methylanthraquinone from StreptomycetesFrom cultures of several streptomycete strains producing isochromanquinone antibiotics (4, 5), 3,8-dihydroxy-1-methylanthraquinone-2-carboxylic acid (2b), one of the rare naturally occurring α-methylanthraquinones, was isolated. Native compounds of this group became known only as insect pigments (e.g. 1d) and later on as constituents of a few plants. A common biosynthesis of benzoisochromanquinones and α-methylanthraquinones is discussed.
    Additional Material: 1 Tab.
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  • 56
    ISSN: 0170-2041
    Keywords: 1,2-Cyclopropanedicarboxylates, cis- and trans- ; Cyclopropanation, large-scale Bonavent-McCoy-Payne cyclopropanation of α,β-unsaturated esters ; cis-trans Separation through distillation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclopropanediamines, 3. - Pure Diastereomers of 1,2-Cyclopropanedicarboxylic Acids and DerivativesEfficient preparations of pure diastereomers of dimethyl 1,2-cyclopropanedicarboxylates 2, dicarboxylic acids 3, dicarbonyl dichlorides 4, and dihydrazides 5 are reported. Mixtures of diastereomers of dimethyl dicarboxylates 2a, b, d, e are obtained from α,β-unsaturated methyl carboxylates 7 and methyl α-chlorocarboxylates 8 as well as from 7c, d and the sulfur ylide 10 (2c, d). The diastereomers are separated by fractionating distillations (2a, b, c, e) or crystallization (2d) on a 100-g to 1-kg scale (d.e. ≥ 99%). Only low yields of 2c are obtained in the reaction of methyl crotonate (7c) with methyl α-chloroacetate (8a), since 7c predominantly dimerizes to afford 12. The diesters 2 are converted into the pure diastereomeric diacids 3, dicarbonyl dichlorides 4, and dihydrazides 5. 3,3-Dimethyl-cis-1,2-cyclopropanedicarboxylic acid (cis-3f) is obtained by trans→cis isomerization of trans-3f with the help of acetic anhydride and sodium acetate as catalyst. The configurations of 2-6 and 12 are confirmed by 1H-NMR spectroscopy. Derivatives of cis-1,2-dimethyl-1,2-cyclopropanedicarboxylic acid tend to form bicyclic products. Thus, the reaction of cis-3e with phosphorus pentachloride yields mainly the cyclic anhydride 6e and only small amounts of the dicarbonyl dichloride cis-4e. Furthermore, the dihydrazide cis-5e slowly cyclizes in the solid state to give the N-aminoimide 13 and hydrazine, a reaction which is fast in solution. Pure 13 is obtained by thermolysis of cis-5e at 60-65°C under high vacuum.
    Notes: Durch Umsetzung von α,β-ungesättigten Estern 7 mit α-Chlorcarbonsäureestern 8 werden die 1,2-Cyclopropandicarbonsäureester 2a, b, d, e erhalten. Aus den α,β-ungesättigten Estern 7c, d und dem Schwefelylid 10 entstehen die 1,2-Cyclopropandicarbon-säureester 2c, d. Die Ester werden durch fraktionierende Destillation (2a, b, c, e) oder Kristallisation (2d) in 100-g- bis 1-kg-Mengen diastereomerenrein erhalten. Crotonsäure-methylester (7c) reagiert nur langsam mit 8a zu 2d, vorwiegend aber mit sich selbst zu 12. Aus den Diestern 2 werden einige Disäuren 3, Dichloride 4 und Dihydrazide 5 diasereomerenrein gewonnen. Durch trans→cis-Isomerisierung von trans-3f mit Acetanhydrid unter Natriumacetat-Katalyse wird die 3,3-Dimethyl-cis-1,2-cyclopropandicarbonsäure (cis-3f) hergestellt. H-NMR-Spektren beweisen die Konfiguration der Verbindungen 2-6 und 12. cis-1,2-Dimethyl-1,2-cyclopropandicarbonsäure-Derivate neigen zum Ringschluß. So entsteht aus der Disäure cis-3e mit Phosphorpentachlorid vorwiegend das cyclische Anhydrid 6e neben wenig Dichlorid cis-4e. Das Dihydrazid cis-5e spaltet im festen Zustand langsam, in Lösung rasch Hydrazin ab und cyclisiert zu 13, das durch Erhitzen von cis-5e auf 60-65°C im Hochvakuum rein erhalten wird.
    Additional Material: 5 Tab.
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  • 57
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 713-717 
    ISSN: 0170-2041
    Keywords: Antibiotics ; Octacidomycin ; Oligocarboxylic acids ; Hexamethylhentetracontane ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Octacidomycin, a New Oligocarboxylic Acid AntibioticThe isolation and structure elucidation of octacidomycin (6), a novel oligocarboxylic acid antibiotic, is described. From NMR and mass spectroscopic studies of its octamethyl ester 1 it can be concluded that in 6 C7- and C5-units are connected to give C47H80O16. Reduction of 1 yields the octaol 2 and from this is obtained its octaacetate 3. Reactions of 2 with hydroiodic acid and lithium aluminium hydride lead - via the octaiodide 4 - to the hitherto unknown 4,10,16,22,28,34-hexamethylhentetracontane (5).
    Notes: Die Isolierung und Strukturaufklärung von Octacidomycin (6), einem neuartigen Oligocarbonsäure-Antibioticum, wird beschrieben. Eingehende NMR- und massenspektrometrische Untersuchungen seines Octamethylesters (1) lassen in 6 auf eine Verknüpfung von C7 und C5-Einheiten zu C47H80O16 schließen. Aus 1 entsteht durch Reduktion das Octaol 2 und daraus dessen Octaacetat 3. Die Umsetzung von 2 mit Iodwasserstoffsäure/Phosphor und Lithiumaluminiumhydrid führt über das Octaiodid 4 zum bislang unbekannten 4,10,16,22,28,34-Hexamethylhentetracontan (5).
    Additional Material: 3 Ill.
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  • 58
    ISSN: 0170-2041
    Keywords: Acrylates, α-tert-butoxy- ; Butenolides, α-tert-butoxy- ; 3-Deoxy-D-manno-2-octulosonic acid (KDO) ; Vinyl carbanions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Functionally Substituted Vinyl Carbanions, 351). - Short Synthesis of 3-Deoxy-D-manno-2-octulosonic Acid (KDO)α-tert-Butoxyacrylic acid (4b) and the amides 4c - 4f are prepared from β-chlorolactate. sec-Butyllithium as a base generated directly the dilithiated species 4b-A - 4e-A in high yields. Reaction of 4c-A - 4e-A with 2,3:4,5-di-O-isopropylidene-D-arabinose (11) as an electrophile gives preferably the D-manno-2-octulosonate derivatives 12c-m - 12e-m. Compound 12c-m is transformed in three convenient, high-yielding steps (ring closure to the butenolide, acid-catalyzed deprotection, and pyranoside formation) into KDO. Correspondingly, D-gluco-KDO is obtained from the D-gluco-configuration byproduct 12c-g.
    Notes: Aus β-Chlormilchsäureester werden α-tert-Butoxyacrylsäure (4b) und die Amide 4c - 4f hergestellt. Mit sec-Butyllithium als Base können daraus direkt und in hoher Ausbeute die dilithiierten Spezies 4b-A - 4f-A erzeugt werden. Durch Reaktion von 4c-A - 4e-A mit 2,3:4,5-Di-O-isopropyliden-D-arabinose (11) als Elektrophil werden bevorzugt die D-manno-2-octulosonsäure-Derivate 12c-m - 12e-m gebildet. Aus 12c-m wird dann in drei einfachen und in hoher Ausbeute verlaufenden Stufen (Ringschluß zum Butenolid, Säure-katalysierte Schutzgruppenabspaltung und Überführung ins Pyranosid) KDO erhalten. Aus der als Nebenprodukt entstandenen D-gluco-Verbindung 12c-g wird entsprechend D-gluco-KDO synthetisiert.
    Additional Material: 1 Tab.
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  • 59
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 83-85 
    ISSN: 0170-2041
    Keywords: Tetrazolo heterocycles ; Tetrazoles, 5-substituted ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Cyclic Systems from Heterocyclic 5-Substituted Tetrazole DerivativesThe easily accessible 5-substituted tetrazole derivatives 1 and 2 react with sodium nitrite, ortho esters, some aldehydes, and bromoacetyl bromide to give the new tetrazolo-triazines 3 or 4, -pyrimidines 5 or 6, -5,6-dihydropyrimidines 7 and -diazepinones 8.
    Additional Material: 2 Tab.
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  • 60
    ISSN: 0170-2041
    Keywords: 1,5-Benzodiazepines, oxygen-bridged ; 1,5-Benzothiazepines, oxygen-bridged ; Calcium entry blockers ; Conformationally restricted heterocycles ; 4-(2-Hydroxyphenyl)-3-buten-2-one ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclocondensation of 4-(2-hydroxyphenyl)-3-buten-2-one (1) with o-aminothiophenol yields 10-methyl-11-oxa-2-thia-9-azatetracyclo[8.7.1.03,8.012,17]octadeca-3,5,7,12,14,16-hexane (2). Similar reaction with o-phenylenediamine affords the 11-oxa-2,9-diaza analogue 3. The 2-hydroxyphenylbutenone 1 and 2-hydroxychalcone (5) show a different bridging ability.
    Additional Material: 2 Ill.
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