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  • 1
    Electronic Resource
    Electronic Resource
    An 1H-NMR. Spectroscopic Study of Alloxazines and Isoalloxazines (1977)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 348-366 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H-NMR.-spectra of a series of alloxazines and isoalloxazines and certain cationic derivatives were investigated (Tab. 2 and 5). Unequivocal assignment of all resonance signals was achieved in some compounds by selective deuteriation also by double resonance technique. The coupling constants were verified by computer simulation. Considerable enhancement of the signals due to H-C(9) and H-C(6) is found on decoupling of H3C-C(7), H3C-C(8) and H3C-N(10), resp. These results are compared with those obtained with FAD. The methyl resonance signal of the H3C-C(7) compounds give doublets due to coupling with H-C(6). The difference in chemical shifts observed upon successive formal introduction of methyl groups into the benzene nucleus of (iso)alloxazines indicates that the molecule becomes less planar thereby. The pyrimidine ring of (iso)alloxazines does not contribute to the ring current except by indirect effects via the carbonyl groups. The experimental data are compared with published MO calculations and discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19770600207
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  • 2
    Electronic Resource
    Electronic Resource
    13C-NMR. Study on Isoalloxazine and Alloxazine Derivatives (1977)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 367-379 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of isoalloxazine and alloxazine derivatives have been investigated by 13C-NMR. The synthesis of selectively 13C-enriched derivatives made it possible to assign unambiguously the signals due to the quaternary carbon atoms at position 4, 4a and 10a of the isoalloxazine ring system. The assignment of the other resonances was ensured by the use of selectively deuteriated and chemically modified compounds as well as by decoupling techniques. The assignments differ in part from those published by Breitmaier & Voelter [2] on FMN and FAD. The solvent dependence of the resonances has been studied in dioxan/water mixtures. The experimental data are compared with published MO calculations and discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19770600208
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  • 3
    Electronic Resource
    Electronic Resource
    Alkali Cation Complexation and Transport Properties of Synthetic Bicyclic Decapeptides: Structural, Thermodynamic, and Kinetic AnalysisThis work was supported by research grants of the Swiss National Science Foundation and the Swiss Federal Institute of Technology. (1979)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2442-2451 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkali cation complexation and bilayer transport by the bicyclic decapeptides S,S′-bis-cyclo-glycyl-L-hemicystyl-glycyl-glycyl-L-prolyl (1), S, S′-bis-cyclo-glycyl-L-hemicystyl-glycyl-glycyl-D-prolyl (2), S, S′-bis-cyclo-glycyl-L- hemicystyl-sarcosyl-sarcosyl-L-prolyl (3), and S, S′-bis-cyclo-glycyl-L-hemicystyl-sarcosyl-sarcosyl-D-prolyl (4) were analyzed according to structural, thermodynamic and kinetic criteria; valinomycin was used as a reference ionophoretic system.Structural analysis of peptide 3 with spectroscopic methods showed different conformational arrangements in the bicyclic system depending on its state of complexation. Circular dichroism indicated the presence of a multitude of conformations with differing helicities around the disulfide bridge in both free and complexed states.Thermodynamic analysis by microcalorimetry demonstrated a far lower cation selectivity among the synthetic peptides than displayed by valinomycin. Peptide 3 shows cation affinities of about two orders of magnitude higher than peptide 4, but still much lower than found for the complexes of valinomycin with K+ and Rb+. In contrast to the latter case, the complexation reactions of peptides 3 and 4 are driven by both enthalpy and entropy contributions. Neither peptide 1 and 2 nor the cyclic partial structures of all four peptides displayed significant cation complexation.A kinetic analysis of the K+-complexation by peptide 3 based on the microcalorimetry experiments showed far lower rates of cation exchange for the synthetic peptide than those reported for valinomycin. Transport studies with peptide 3 using artificial lipid bilayer membranes gave negative results. The apparent lack of ionophoretic properties of these synthetic peptides despite their considerable ability to form complexes with cations is discussed in terms of structural parameters.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19790620739
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of Abscisic Acid (1976)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 59 (1976), S. 1424-1427 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A stereoselective synthesis of (±)-abscisic acid (7) is described in which 2-cis 3-methylpent-2-en-4-yn-1-ol (2) is used to introduce the 2-cis, 4-trans geometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19760590503
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  • 5
    Electronic Resource
    Electronic Resource
    Regioselektive Funktionalisierung nicht aktivierter CH-Bindungen, 4. Photoreaktionen amphiphiler Benzophenon- und Myristinsäurederivate in Micellen und Doppelschichtmembranen (1987)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 597-606 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Regioselective Functionalization of Nonactivated CH-Bonds, 4. - Photoreactions of Amphiphilic Derivatives of Benzophenonecarboxylic Acid and Myristic Acid Derivatives in Micelles and BilayersAmphiphilic derivatives of benzophenonecarboxylic acid and myristic acid in micelles, vesicles, and multilamellar aggregates were photochemically converted into tertiary alcohols, the workup of which yielded mixtures of the isomeric ketomyristic acid methyl esters 5. A slightly increased but none the less low selectivity was found in bilayers in comparison with micelles. Various amphiphilic head groups shifted the center of attack. Low total yields, especially in bilayers, can be attributed to a predominant reaction between the benzophenone substituents. By preparation of the corresponding reference compounds it could be demonstrated that benzhydrols (8a-d) or benzpinacols (9a-c) are not formed in this unexpected reaction.
    Notes: Amphiphile Benzophenon- und Myristinsäurederivate wurden in Micellen, Vesikeln und multilamellaren Aggregaten photochemisch zu tertiären Alkoholen umgesetzt, deren Aufarbeitung zu Gemischen isomerer Ketomyristinsäure-methylester 5 führte. In Doppelschichtmembranen wurde eine gegenüber Micellen geringfügig erhöhte, insgesamt aber niedrige Selektivität erhalten. Die Verwendung unterschiedlicher Amphiphil-Kopfgruppen führte zur Verschiebung des Angriffsschwerpunktes. Die besonders in Doppelschichtmembranen geringen Gesamtausbeuten lassen sich auf eine bevorzugte Reaktion der Benzophenonreste untereinander zurückführen. Durch Darstellung entsprechender Referenzverbindungen konnte gezeigt werden, daß die Bildung von Benzhydrolen (8a-d) oder Benzpinakolen (9a-c) bei dieser unerwarteten Reaktion keine Rolle spielt.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198719870706
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  • 6
    Electronic Resource
    Electronic Resource
    Glycosidation, VII. Development of Selective Cytostatica for Cancer Therapy Synthesis of Acetal-β-glucosides from Cytotoxic Aldehydes (1987)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 847-856 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Glycosidierungen, VII. - Entwicklung selektiver Cytostatica für die Krebs-Therapie. - Synthese von Acetal-β-glucosiden von cytotoxischen AldehydenAldehyde sind stark cytotoxische Verbindungen, die jedoch normalerweise nicht für die Krebs-Therapie eingesetzt werden können, da sie schnell durch Bindung an Serumproteine desaktiviert werden. Es besteht jedoch die Möglichkeit, sie in Acetal-β-D-glucoside, eine nicht toxische Transportform, zu überführen, aus der sie durch enzymatische oder säurekatalysierte Hydrolyse freigesetzt werden können. Die acetylgeschützten Acetal-β-glucoside 4 werden in sehr guten Ausbeuten und hochselektiv durch Umsetzung von Trimethylsilyl-2,3,4,6-tetra-O-acetyl-β-D-glucopyranosid (1c) und einem Acetal 2 in Gegenwart katalytischer Mengen von Trimethylsilyl-trifluormethansulfonat (3) in Dichlormethan bei -70°C erhalten. Entacetylierung ergibt die freien Acetal-β-glucoside 5. In ähnlicher Weise kann Trimethylsilyl-2,3,4,6-tetra-O-benzyl-β-D-glucopyranosid (1e) zu den benzylgeschützten Acetal-β-glucosiden 6 umgesetzt werden. Die Bildung von 4 oder 6 gelingt auch durch Reaktion von 1c oder 1e mit Aldehyden 8 und Alkyltrimethylsilylethern 7 in Gegenwart von 3.
    Notes: Aldehydes are highly cytotoxic compounds, but they can normally not be used in cancer therapy because of fast binding to serum proteins. However, they could be transformed into acetal-β-glucosides 5, a nontoxic transport form, from which they can be freed by enzymatic or acid-catalyzed hydrolysis. The acetyl-protected acetal-β-glucosides 4 are obtained in excellent yield and highly selectively by reaction of trimethylsilyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside (1c) and an acetal 2 in the presence of catalytic amounts of trimethylsilyl trifluoromethanesulfonate (3) in dichloromethane at -70°C. Deacetylation gives the free acetal-β-glucosides 5. Similarly, trimethylsilyl 2,3,4,6-tetra-O-benzyl-β-glucopyranoside (1e) was used to afford the benzyl-protected acetal-β-glucosides 6. The formation of 4 or 6 can also be achieved by reaction of 1c or 1e with an aldehyde 8 and an alkyl trimethylsilyl ether 7 in the presence of 3.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198719870839
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  • 7
    Electronic Resource
    Electronic Resource
    Conversion of oleic acid to 17- and 18-substituted stearic acid derivatives by way of the „acetylene zipper“ (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 1037-1040 
    Details
    ISSN: 0170-2041
    Keywords: Fatty acid ; Oleic acid ; Stearic acid, 17- and 18-substituted ; Acetylene zipper ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stearolic acid (2) was prepared from oleic acid (1) and converted to 4, 5, and 7 by way of the „acetylene zipper“ reaction. Compounds 5 and 7 were transformed to the (ω - 1) ketones 8 and 9 and dimerized by way of the Glaser coupling reaction to 11 and 12. At daylight, 12 polymerizes to a blue polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1991199101178
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  • 8
    Electronic Resource
    Electronic Resource
    Anodische Oxidation organischer Verbindungen, 23 Anodische Addition von Harnstoffen und Ethylenglykol an konjugierte Diene (1979)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1979 (1979), S. 318-327 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Anodic Oxidation of Organic Compounds, 23.  -  Anodic Addition of Ureas and Ethylene Glycol to Conjugated DienesThe anodic addition of 1,3-dimethylurea (4b) to 2,4-hexadiene (9), 2-methyl-2,4-hexadiene (10), 2,5-dimethyl-2,4-hexadiene (11), 1,3-cyclohexadiene (12), 1,4-diphenylbutadiene (13) and trans-stilbene (14) yields 4,5-disubstituted 1,3-dimethylimidazolidin-2-ones 16-23. Analogously 1,3-diphenylbutadiene (4c) adds to 9 to form 5-methyl-1,3-diphenyl-4-(1-propenyl)imidazolidin-2-one (24). Urea (4a) and 1,3-diacetylurea (4d) fail to react as a consequence of their insufficient nucleophilicity, N,N'-diacetylethylenediamine (4h) and 1,2-diacetylhydrazine (4g) do not undergo addition owing to their very low solubility in acetonitrile. In an electrolyte consisting of ethylene glycol/acetonitrile, 2,4-hexadiene (9) and 1,3-butadiene (8) afford the glycol ethers 25-28. The formation of all products can be explained in terms of a radical cation 29 as first intermediate.
    Notes: Die anodische Addition von 1,3-Dimethylharnstoff (4b) an 2,4-Hexadien (9), 2-Methyl-2,4-hexadien (10), 2,5-Dimethyl-2,4-hexadien (11), 1,3-Cyclohexadien (12), 1,4-Diphenylbutadien (13) und trans-Stilben (14) führt zu den 4,5-disubstituierten 1,3-Dimethylimidazolidin-2-onen 16-23. 1,3-Diphenylharnstoff (4c) addiert sich analog an 9 zu 5-Methyl-1,3-diphenyl-4-(1-propenyl)imidazolidin-2-on (24). Harnstoff (4a) und 1,3-Diacetylharnstoff (4d) lassen sich infolge zu geringer Nucleophilie, N,N'-Diacetylethylendiamin (4h) und 1,2-Diacetylhydrazin (4g) infolge zu geringer Löslichkeit in Acetoniril nicht anodisch mit 2,4-Hexadien (9) umsetzen. In einem Elektrolyten aus Ethylenglykol/Acetonitril entstehen aus 2,4-Hexadien (9) und 1,3-Butadien (8) die Glykolether 25-28. Alle Produkte lassen sich über ein primäres Radikalkation 29 erklären.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197919790304
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  • 9
    Electronic Resource
    Electronic Resource
    Enzym-katalysierte asymmetrische Synthese, IV. Synthese homochiraler Bausteine für die enantioselektive Totalsynthese von Cyclopentanoiden mit Esterase-katalysierter asymmetrischer Schlüsselreaktion (1986)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 687-716 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Enzyme-catalysed Asymmetric Synthesis, IV.  -  Synthesis of Homochiral Building Blocks for the Enantioselective Total Synthesis of Cyclopentanoids with an Esterase-catalysed Asymmetric Reaction as Key StepAn efficient synthesis of the homochiral building blocks 2a and ent-2a based on the “enantiotopos-enzyme concept” for the total synthesis of cyclopentanoids is described. Key steps thereof are the almost quantitative PLE-catalysed asymmetric hydrolysis of the meso-diester 8 to the homochiral hemiester 9, whose absolute configuration was determined by crystal structure analysis of the (-)-ephedrine salt 12, the preparation of optically pure 9 and ent-9 by a racemate resolution of rac-9 using (+)- and (-)-ephedrine, the enantiodivergent synthesis of the lactones 18 and ent-18 from 9, as well as the enantioconvergent synthesis of 18 or ent-18 from 9 and ent-9 by optional chemoselective reduction of the ester and carboxy group, and finally the regioselective Dieckmann cyclisation of the isomeric diesters 23b/24b and ent-23b/ent-24b, respectively, to give the cyclopentanoid target compounds 2a and ent-2a. The structures of 23b, 24b, rac-2b, and rac-29 were determined by INADEQUATE-13C-NMR experiments. Dieckmann cyclisation of the trans-diester rac-31 also leads to rac-2a and rac-26a.
    Notes: Eine ausgefeilte Synthese der homochiralen Bausteine 2a und ent-2a mittels der „Enantiotopos-Enzym-Konzeption“ für die enantioselektive Totalsynthese von Cyclopentanoiden wird beschrieben. Deren Schlüsselschritte sind die nahezu quantitative, PLE-katalysierte asymmetrische Verseifung des meso-Diesters 8 zum homochiralen Halbester 9, dessen Absolutkonfiguration durch Röntgenstruktur-Analyse des (-)-Ephedrinsalzes 12 bestimmt wurde; die Gewinnung von optisch reinem 9 und ent-9 durch Racematspaltung von rac-9 mit (+)- und (-)-Ephedrin; die enantiodivergente Synthese der Lactone 18 und ent-18 aus 9 sowie die enantiokonvergente Synthese von 18 oder ent-18 aus 9 sowie die enantiokonvergente Synthese von 18 oder ent-18 aus 9 und ent-9 durch wahlweise chemoselektive Reduktion der Ester- und Carboxygruppe und schließlich die regioselektive Dieckmann-Cyclisierung der isomeren Diester 23b/24b bzw. ent-23b/ent-24b zu den cyclopentanoiden Zielverbindungen 2a und ent-2a. Die Strukturen von 23b, 24b, rac-2b und rac-29 wurden durch INADEQUATE-13C-NMR-Experimente bestimmt. Dieckmann-Cyclisierung des trans-Diesters rac-31 führt ebenfalls zu rac-2a und rac-26a.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198619860410
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  • 10
    Electronic Resource
    Electronic Resource
    Orthoamide, XLII. Umsetzungen von Dinitrilen mit Orthoamid-Derivaten der Ameisen- und Kohlensäure (1985)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1985 (1985), S. 1804-1816 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Orthoamides, XLII.  -  Reactions of Dinitriles with Orthoamide Derivatives of Formic and Carbonic AcidSuccinodinitrile (5a) reacts with the orthocarbonic acid derivative 1a to give the guanidinium salt 6. Glutarodinitrile (5b) on reaction with 1a yields the benzonitrile 9. In the reaction of adipodinitrile (5c) and pimelodinitrile (5d) with 1a the ene-guanidino nitriles 10a and b, respectively, are produced. The higher homologous dinitriles 5e - h condense with 1a to give the ketene aminals 11a - d. The ene-guanidino nitriles 10 are transformed by alkylating reagents into guanidinium salts 13. Enamino nitriles 16 are obtained by reaction of the dinitriles 5 with orthoformic acid derivatives 3 in a molar ratio of 1:1. With excess orthoformic acid derivatives 3 (molar ratio 2:1) the dinitriles 5 condense to afford the compounds 18.
    Notes: Bernsteinsäuredinitril (5a) reagiert mit dem Orthokohlensäurederivat 1a zu dem Guanidiniumsalz 6. Glutarsäuredinitril (5b) ergibt bei der Umsetzung mit 1a das Benzonitril 9. Adipinsäuredinitril (5c) und Pimelinsäuredinitril (5d) setzen sich mit 1a zu den En-Guanidinonitrilen 10a, b um. Die höheren Dinitrile 5e - h kondensieren mit 1a zu den Ketenaminalen 11a - d. Die En-Guanidinonitrile 10 werden durch Alkylierungsmittel in die Guanidiniumsalze 13 übergeführt. Orthoameisensäurederivate 3 reagieren mit den Dinitrilen 5 zu den Enamino-dinitrilen 16, wenn mit dem Molverhältnis 1:1 gearbeitet wird. Umsetzung mit dem Molverhältnis 2:1 liefert die Kondensationsprodukte 18.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198519850908
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