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  • 1
    Electronic Resource
    Electronic Resource
    Berichtigung zu dem Beitrag. Enzym-katalysierte asymmetrische Synthese, IV Synthese homochiraler Bausteine für die enantioselektive Totalsynthese von Cyclopentanoiden mit Esterasekatalysierter asymmetrischer Schlüsselreaktion (1986)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 1316-1316 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198619860716
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Conversion of Fatty Acids and Derivatives, IV. Conversion of Fatty Acid Methyl Esters into Dialkylated Succinic Esters by Oxidative Coupling of their Enolates (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 1219-1223 
    Details
    ISSN: 0170-2041
    Keywords: Fatty acid methyl esters ; Enolates ; Oxidative coupling ; Succinic acid diesters ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enolates of fatty acid methyl esters 1a-g are dimerized in good yields (56 to 73%) by means of oxidative coupling with copper(II) bromide to dialkylated succinic esters 2a-g. The configuration of meso-2a was established by independent synthesis. On treatment with ozone the unsaturated dimer 2c is converted to the tetracarboxyl compound 6. Epoxidation of 2g leads to the corresponding bisepoxy diester 7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1993199301197
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Synthesen, spektroskopische Untersuchungen und Prüfung auf antibakterielle Wirksamkeit von einigen Pfeffer-Alkaloiden. Olefinierungsreaktionen mit Phosphorylacetamiden (1982)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1982 (1982), S. 1142-1149 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis, Spectroscopic Examination, and Testing for Antibacterial Activity of Some Pepper Alkaloids. Olefination Reactions with Phosphorylacetamides4,5-Dihydrowisanine (4) and 4,5-dihydrookolasine (3) as well as 1-(2-methoxy-4,5-methylene-dioxycinnamoyl)piperidine (5) are three alkaloids which have been isolated from Piper guineense and Piper peepuloides, respectively. They have been synthesized by Horner-Wittig reaction of 3-(2-methoxy-4,5-methylenedioxyphenyl)propionaldehyde (11) and 2-methoxy-4,5-methylene-dioxybenzaldehyde (8) with 1-(diethoxyphosphorylacetyl)piperidine (6) and -pyrrolidine (7), respectively. The Horner-Wittig reaction gave products having E-configuration. The amides are not or only slightly active against bacteria.
    Notes: 4,5-Dihydrowisanin (4) und 4,5-Dihydrookolasin (3) sowie 2-Methoxy-4,5-methylendioxyzimtsäure-piperidid (5) sind drei aus Piper guineense bzw. Piper peepuloides isolierte Alkaloide. Sie wurden durch Horner-Wittig-Reaktion von 3-(2-Methoxy-4,5-methylendioxyphenyl)propionaldehyd (11) bzw. 2-Methoxy-4,5-methylendioxybenzaldehyd (8) mit 1-(Diethoxyphosphoryl-acetyl)piperidin (7) bzw. -pyrrolidin (6) hergestellt. Die Horner-Wittig-Reaktion ergab Verbindungen mit E-Konfiguration. Die Amide sind nicht oder nur schwach antibakteriell wirksam.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198219820615
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  • 6
    Electronic Resource
    Electronic Resource
    Pheromone, 7. Kolbe-Synthese von 29-tert-Butyldimethylsilyloxy-3,11-dimethyl-1-nonacosen, einer Schlüsselverbindung zur Darstellung eines optisch aktiven Sexuallockstoffes der Deutschen Hausschabe (1982)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1982 (1982), S. 1532-1542 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Pheromones, 7.  -  Kolbe Synthesis of 29-tert-Butyldimethylsilyloxy-3,11-dimethyl-1-nonacosene, a Key Intermediate for the Preparation of an Optically Active Pheromone of the German Cockroach29-tert-butyldimethylsilyloxy-3,11-dimethyl-1-nonacosene (17) is synthesized by Grignard coupling of p-tolyl (S)-24-tert-butyldimethylsilyloxy-6-methyl-1-tetracosanesulfonate (15) with 5-bromo-3-methyl-1-pentene (16). The tosylate is prepared from methyl (S)-24-hydroxy-6-methyltetracosanate (11) by protection of the free hydroxyl group and reduction of the ester function. The ester 11 is obtained by twofold Kolbe electrolysis of 18-hydroxyoctadecanoic acid (5) with methyl (S)-3-methylglutarate (6) and with methyl glutarate (9). The bromide 16 is also sythesized from the half-ester 6 by reduction of the ester function and elimination of phenyl selenide.
    Notes: 29-tert-Butyldimethylsilyloxy-3,11-dimethyl-1-nonacosen (17) wird durch Grignardkupplung von p-Tolyl-(S)-24-tert-butyldimethylsilyloxy-6-methyl-1-tetracosansulfonat (15) mit 5-Brom-3-methyl-1-penten (16) synthetisiert. Das Tosylat 15 ist aus (S)-24-Hydroxy-6-methyltetracosansäure-methylester (11) durch Schutz der freien Hydroxylgruppe und Reduktion der Esterfunktion mit anschließender Tosylierung erhältlich. Der Ester 11 wird durch doppelte Kolbe-Elektrolyse von 18-Hydroxyoctadecansäure (5) mit (S)-3-Methylglutarsäure-monomethylester (6) und an-schließend mit Glutarsäure-monomethylester (9) aufgebaut. Das Bromid 16 wird ebenfalls aus dem Halbester 6 durch Reduktion der Esterfunktion und Phenylselenid-Eliminierung synthetisiert.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198219820812
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  • 7
    Electronic Resource
    Electronic Resource
    Enantioselektive Synthese von Cyclopentanoiden, II. Asymmetrische Synthese eines neuen homochiralen Prostaglandin-Bausteins via Brükenkopf-Enolate mit Bicyclo[3.3.0]octan-Gerüst (1986)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 1179-1212 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Enantioselective Synthesis of Cyclopentanoids, II. - Asymmetric Synthesis of a Novel Homochiral Prostaglandin Building Unit via Bridgehead Enolates with Bicyclo[3.3.0]octane SkeletonStarting from the enantiomerically pure 1H-cyclopenta[c]furanone derivative 7a a new prostaglandin building block, the homochiral α-methylenecyclopentanone 1, which should allow the enantioselective synthesis of prostaglandins 5 and prostacyclins 6, has been synthesized via the 1H-cyclopenta[c]furanone derivatives 8a, 11a, and 20 and the cyclopentane derivatives 23 and 24. The configuration and conformations of the hydroxy ester derivatives 8 and 9, which establish the stereochemistry of 1, have been determined by X-ray structural analysis, 1H-NMR spectroscopy, and force-field calculations. The key step of the sequence leading to 1 is the hydroxylation of the bridgehead enolate 19 to yield the hydroxy lactone 20. Investigations of 19 and the analogous enolates 13a - c in connection with literature data reveal that bridgehead enolates of the bicycle[3.3.0]octane type react with electrophiles with over 95% diastereofacial selectivity to give the cis-fused bridgehead-substituted bicycle[3.3.0]octane derivatives. Force-field calculations of the enolates 17a and 18 indicate that the high π-facial selection of 13, 19, and analogous enolates is due not only to steric but also to stereoelectronic effects, because contrary to 18 a nonplanar enolate fragment was found for 17a, - 1 reacts with the cuprate 25 to yield the homochiral cyclopentanone derivative 26 having 2α-configuration. With the synthesis of 29c from 11a protocol for the stereoselective attachment of ω-side chains to 3 was successfully tested.
    Notes: Ausgehend von dem enantiomerenreinen 1H-Cyclopenta[c]furanon-Derivat 7a gelingt über die Stufen der 1H-Cyclopenta[c]furanon-Derivate 8a, 11a und 20 sowie der Cyclopentan-Derivate 23 und 24 die Synthese eines neuen Prostaglandin-Bausteins, des homochiralen α-Methylencyclopentanons 1, das in einer 1,4-Additions-Carbonylolefinierungs-Sequenz die enantioselektive Synthese von Prostaglandinen 5 und Prostacyclinen 6 ermöglichen sollte. Konfiguration und Konformationen der Hydroxyester-Derivate 8 und 9, die die Stereochemie von 1 festlegen, wurden durch Röntgenstruktur-Analyse, 1H-NMR-Spektroskopie und Kraftfeldrechnungen ermittelt. Zentraler Schritt der zu 1 führenden Synthesefolge ist die Hydroxylierung des Brückenkopf-Enolates 19 zum Hydroxylacton 20. Untersuchungen an 19 und den analogen Enolaten 13a - c in Verbindung mit Literaturdaten ergeben, daß Brückenkopf-Enolate von Bicyclo[3.3.0]octan-Typ mit Elektrophilen mit über 95% diastereofacialer Selektivität zu den cis-verknüpften substituierten Bicyclen reagieren. Nach Kraftfeldrechnungen der Enolate 17a und 18 sind für die hohe π-faciale Selektion von 13a - c, 19 und analoger Verbindungen vermutlich nicht nur sterische sondern auch stereoelektronische Gründe maßgebend, da für 17a im Gegensatz zu 18 ein nichtplanares Enolat-Fragment resultiert. - 1 reagiert mit dem Cuprat 25 zum homochiralen Cyclopentanon-Derivat 26 mit 2α-Konfiguration. Mit der Synthese von 29c aus 11a wurde ein Weg zur stereoselektiven Anbindung von ω-Seitenketten an 3 erfolgreich erprobt.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198619860706
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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Regioselective Conversion of Nonactivated CH Bonds, VI. Selective ω- to (ω - 2)-Chlorination of Fatty Acids by Way of Adsorption on Alumina (1992)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 559-563 
    Details
    ISSN: 0170-2041
    Keywords: Fatty acids ; Chlorination, selective ; Lactones ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fatty acids 4-7 can be chlorinated with high selectivity in the (ω  -  2)- to ω-position. For that purpose the acid is adsorbed on alumina and allowed to react with gaseous chlorine or t-BuOCl at 20 and -35°C. The resulting chloroalkanoic acids 10-13 can be converted into macrocyclic lactones 14-17 by treatment with DBU.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199219920197
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  • 10
    Electronic Resource
    Electronic Resource
    Electroorganic Synthesis, 54. Enantioselective Cathodic Reduction of 4-Substituted Coumarins with Alkaloids as Catalysts, 1Dedicated to Professor Dr. Ulrich Schöllkopf on the occasion of his 65th birthday. (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 601-607 
    Details
    ISSN: 0170-2041
    Keywords: Electrochemistry ; Coumarins, reduction of ; Enantioselective protonation ; Alkaloids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optical yield in the alkaloid-catalyzed enantioselective electroreduction of 4-methylcoumarin (1a) was increased from 17% to 47.4% by systematic variation of the electrolysis conditions. The results are explained by an induction mechanism in which the adsorbed protonated alkaloid acts as a chiral proton donor towards a prochiral carbanion derived from 1a. The preferred configuration of the product and the results obtained by variation of the alkaloid structure allow us to propose a model of the transition state. Furthermore, 4-phenylcoumarin (1b) and 4-(trifluoromethyl)coumarin (1c) were reduced with 13.2% and 8.4% ee, respectively.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199319930198
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