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  • Articles: DFG German National Licenses  (3)
  • Glycosphingolipids  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 217-224 
    ISSN: 0170-2041
    Keywords: Glycosphingolipids ; Globo- and isoglobo series ; Azidosphingosine glycosylation procedure ; Glycosylation, inverted procedure for ; Lysoglycosphingolipid ; Ceramides ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of globotriaosylceramide (1) was based on O-galactosyl trichloroacetimidate 5α as donor and 4b-O-unprotected lactose 7 as acceptor; 7 was readily accessible from lactose. Glycosylation by an “inverted procedure” afforded preferentially the α-trisaccharide 8α. Its transformation into the O-acetyl-protected trichloroacetimidate 11α led to an efficient triaosyl donor for the β-selective glycosylation of 3-O-benzoyl-azidosphingosine 12. The obtained lysoglycosphingolipid derivative 13 was directly converted into the N-palmitoyl derivative 14 which gave upon O-deacylation the target molecule 1. For the synthesis of isoglobotriaosylceramide (2) essentially the same procedure was applied. Thus, by starting from 5α and 3b, 4b-O-unprotected lactose acceptor 15 the use of the inverted procedure for glycoside-bond formation gave preferentially trisaccharide 16α, which was transformed into triaosyl donor 24α. Application of the azidosphingosine glycosylation procedure afforded lysosphingolipid 25 and subsequently glycosphingolipid 26; after deprotection the target molecule 2 was obtained.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 699-708 
    ISSN: 0170-2041
    Keywords: Carbohydrates ; Trichloroacetimidates ; Azidosphingosines ; Glycosphingolipids ; Enzyme inhibitors ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: D-Glucose was transformed into the 4-deoxy-4-C-methylene derivative 1. Dihydroxylation of 1 and then selective O-tosylation afforded 4-C-(tosyloxymethyl)glucoside 3. Subsequent hydrogenolytic O-debenzylation, selective O-acetylation, treatment with a base, selective removal of the anomeric O-acetyl group, and then treatment with trichloroacetonitrile in the presence of a base furnished 4-epoxy-4-C-methyleneglucosyl donor 7 (α,β mixture). Reaction of 7 with 3-O-acyl-protected azidosphingosines 8a-c in the presence of Et2O.BF3 gave β-glycosides 9a-c. Compounds 9a-c were transformed into the corresponding glucosylceramide derivatives 10a-c by treatment with triphenylphosphane/water and acyl anhydrides. Satisfactory removal of the O-benzoyl protective group was difficult; however, O-acetyl and O-isobutyryl protective groups could be removed by methanolysis, thus affording from 10b, c the target molecules 11 and 12 with varying alkyl-chain length. The epoxide 16 with galacto configuration, readily obtained from 1, on treatment with p-toluenesulfonic acid furnished 4-C-(tosyloxymethyl)galactoside 18; this was transformed, as outlined for 3, into the target molecules 25b, c having galacto configuration in the sugar moiety.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 859-864 
    ISSN: 0170-2041
    Keywords: Glycosphingolipids ; Ganglio series ; Blood group B determinant ; Glycosides ; Trichloroacetimidates ; Saccharides ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the O-acetyl protected heptasaccharide moiety (2) of BGM1 was performed according to the following reaction sequence: Reaction of 2,3-di-O-acetyl-4,6-O-benzylidenegalactosyl trichloroacetimidate 4 (as donor) with 3-O-unprotected 2-azidogalactose 5 (as acceptor) gave β(1→3)-connected disaccharide 6. Subsequent O-deacetylation followed by reaction with galactosyl donor 8 afforded regioselectively trisaccharide 9 which was converted into tetrasaccharide 12 by treatment with fucosyl donor 11. Transformation of 12 via acid-catalyzed O-deisopropylidenation, O-acetylation, anomeric O-desilylation, and then base-catalyzed treatment with trichloroacetonitrile afforded trichloroacetimidate 16 as tetraosyl donor. Reaction of 16 with the known 4b-O-unprotected sialyllactose derivative 17 gave in acetonitrile at -40°C in the presence of TMSOTf as the catalyst the desired heptasaccharide 18. Azido group reduction with propanedithiol, N-acetylation, hydrogenolytic O-debenzylation, and O-debenzylidenation under acidic conditions followed by O-acetylation afforded the target molecule 2. The structural assignments were based on the 1H-NMR data.
    Type of Medium: Electronic Resource
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