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  • Organic Chemistry  (3)
  • Glycosides, pyruvylated  (1)
  • Glycosyl donors, pyruvylated  (1)
  • 1990-1994  (3)
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  • 1
    Digitale Medien
    Digitale Medien
    Lewis Acid-Catalysed Anomerisation and Rearrangement of Alkyl D-Glycopyranosides During Acetalisation with Methyl Pyruvate: How to Utilise it for the Preparation of 1-(Carboxyethylidene)glycopyranosyl DonorsPresented in part at the VIth European Carbohydrate Symposium, Edinburgh 1991. (1992)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 441-451 
    Details
    ISSN: 0170-2041
    Schlagwort(e): Anomerization ; Glycosides ; Glycosyl donors, pyruvylated ; Carbohydrates ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The preparation of 4,6-O-(1-methoxycarbonylethylidene)-D-glycopyranosides 5 starting from 2,3-di-O-benzoyl-D-glycopyranosides 1 and their 4,6-bis-O-trimethylsilyl ethers 2 using methyl 2,2-bis(phenylthio)propionate (4) and methyl pyruvate (3), respectively, under Lewis acid catalysis conditions is described. In the D-gluco series anomerisation of alkyl β-D-glucopyranosides is observed as a side reaction, giving complex mixtures and low yields of the title compounds whereas alkyl-α-D-glucopyranosides and alkyl or phenyl 1-thio-β-D-glucopyranosides react without anomerisation. The reactions are accompanied by isomerisation of the initially formed diastereomer (R)-5 having an equatorial methoxycarbonyl group to the thermodynamically favoured diastereomer (S)-5 having the methoxycarbonyl group in an axial position. In the D-galacto series similar side reactions are observed accompanied by rearrangement to furanosides 9 of alkyl and phenyl β-D-galactopyranosides. The results are used for efficient syntheses of two protected disaccharides 8 and 11 representing structural fragments of the polysaccharide repeating units of Mycobacteria and Rhizobia via pyruvate acetal-containing glucosyl and galactosyl donors 7 and 10.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.199219920180
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Enzym-katalysierte Reaktionen, 7. Enantioselektive Veresterung racemischer Cyanhydrine und enantioselektive Hydrolyse oder Umesterung racemischer Cyanhydrinester mittels Lipasen (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 47-54 
    Details
    ISSN: 0170-2041
    Schlagwort(e): Cyanohydrins and cyanohydrin esters, optically active ; Resolutions, kinetic enzyme-catalyzed ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Enzyme-Catalyzed Reactions, 71). - Enantioselective Esterification of Racemic Cyanohydrins and Enantioselective Hydrolysis or Transesterification of Cyanohydrin Esters by LipasesPure cyanohydrin enantiomers (S)-1/(R)-1 and their O-acyl derivatives (R)-3/(S)-3 are obtained from three different lipasecatalyzed reactions: i) enantioselective hydrolysis of aliphatic and aromatic racemic cyanohydrin esters 3, ii) enantioselective acylation of racemic cyanohydrins 1, iii) enantioselective transesterification of 3 with primary alcohols. Both the cyanohydrin esters and the free cyanohydrins (which are prone to racemization) are isolated as enantiomers with high optical purity on a preparative scale. Hydrolysis of the racemic butyrates 3b, e with Candida cylindracea lipase and pseudomonas sp. lipase, respectively, for example, affords the free (S)-cyanohydrins (S)-2-hydroxypentanenitril [(S)-1a] and (S)-mandelonitrile [(S)-1b)] in high yield with 97 and 96% ee, respectively. (S)-1a is obtained with the same optical purity by candida sp. lipase-catalyzed transesterification of 3b with 1-octanol.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.199119910108
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Unexpected Formation of 3,6-Anhydrofuranoses by Acid Treatment of Methyl 2,3-Di-O-acyl-D-glycopyranosides (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 255-260 
    Details
    ISSN: 0170-2041
    Schlagwort(e): Carbohydrates ; Furanoses, 3,6-anhydro ; Glycosides, pyruvylated ; Anhydrofuranoses ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Treatment of methyl 2,3-di-O-acyl-D-glycopyranosides 1 of glucose and mannose with catalytic amounts of trifluoromethanesulfonic acid afforded the corresponding bis(5-O-acyl-3,6-anhydro-D-glycofuranose) 1,2′:2,1′-dianhydrides 6 in 12-58% yield the structure of which was confirmed for the α-D-glucose derivative 6a by an X-ray analysis. In addition, in the presence of methyl pyruvate (2a) or methyl 2-acetoxy-acrylate (2b) various amounts of diastereomeric 3,6-anhydro-5-O-benzoyl-1,2-O-(1-methoxycarbonyl)ethylidene-α-D-glucofuranoses 5 and acylated methyl α-D-glucopyranosides 3 and 4, respectively, were formed.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.199319930145
    Standort Signatur Erwartet Verfügbarkeit
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