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  • Articles: DFG German National Licenses  (4)
  • O-Glycosyl trichloroacetimidates  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Glycosyl imidates, 73. Synthesis of ganglioside gm1 via a GA1 intermediate (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 2101-2111 
    Details
    ISSN: 0947-3440
    Keywords: Glycosylsphingolipids ; Ganglio series ; Glycoside synthesis ; O-Glycosyl trichloroacetimidates ; Sialyl phosphite ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of GM1 pentasaccharide 36 via GA1-intermediate 24 was based on lactose building block 11, Galβ(1-3)-GalN3 building block 23, and sialyl donors 32. For the synthesis of 11, tetra-O-acetyl galactosyl trichloroacetimidate 3 or 2,3-di-O-acetyl-4,6-O-benzylidene-galactosyl trichloroacetimidate 5 as donors were allowed to react with 4-O-unprotected glucose derivative 4 as acceptor to afford lactose derivatives 6 and 7, respectively, in high yields. They were readily transformed via 8 into 2b,3b-O-MPM-protected 9; reductive opening of the dioxane ring with DIBAH furnished regioselectively the desired 4b-O-unprotected lactose derivative 11. From donor 3 and 6-O-benzoyl-protected 2-azidoglucose 19 as acceptor Galβ(1-3)GalN3 disaccharide 20 was synthesized which was readily converted into per-O-acylprotected trichloroacetimidate 23. Reaction of 23 with 11 afforded upon Sn(OTf)2 catalysis the desired β-linked tetrasaccharide 24 in high yield. Removal of the MPM-protective groups with DDQ furnished 2b,3b-O-unprotected derivative 31, which gave by treatment with sialyl donors 32a and 32b GM1-pentasaccharide intermediate 33 in good yield. 2b-O-Acetylation and then hydrogenolysis in the presence of Pearlman's catalyst and ensuing peracetylation afforded O-acyl-protected GM1-pentasaccharide 36 which was already previously converted into GM1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199512296
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    C-Glycosides of Visnagin Analogues (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2317-2322 
    Details
    ISSN: 1434-193X
    Keywords: C-Glycosyl compounds ; Flavones ; Flavanones ; O-Glycosyl trichloroacetimidates ; Fries rearrangement ; Carbohydrates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Glycosylation of the visnagin cleavage product 2 with O-acetyl-protected glycosyl donor 5a afforded O-glycoside 6a, which could be transformed into the O-benzyl-protected compound 6b. The latter underwent Fries-type rearrangement to afford C-glycoside 4b. The same product could be obtained directly from 2 and O-benzyl-protected glycosyl donor 5b. Reaction of 4b with benzaldehyde and anisaldehyde furnished chalcones 7A,B, which, upon treatment with base, furnished flavanone C-glycosides 10A,B. Selenium dioxide oxidation of 10A,B or of 7A,B led to the corresponding flavone C-glycosides 11A,B. The same result was obtained by Baker-Venkataraman rearrangement; on treatment with base, the O-aroyl compounds 12A-C gave C-aroyl compounds 13A-C, which, on addition of TMSOTf, furnished flavone C-glycosides 11A-C. Hydrogenolytic O-debenzylation of 11A afforded target molecule 3A, which was transformed into O-acetyl derivative 14A for characterization. Structural assignments of all compounds were based on 1H-NMR data.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Glycosyl imidates. 49. Synthesis of the octasaccharide moiety of the dimeric Lex antigen (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 425-433 
    Details
    ISSN: 0170-2041
    Keywords: Lewis antigen X ; O-Glycosyl trichloroacetimidates ; Glycosylation procedure, inverted ; O-Protection, selective ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A versatile synthesis of the basic Galβ (1→4)[Fucα(1→3)]-GlcNAc trisaccharide building block of the Lex antigen family based on two important findings could be developed. Firstly, selective 3-O-allylation of the readily available azidolactose derivative 3 led to an efficient synthesis of the 3-O-unprotected fucosyl acceptor 9. Secondly, α-fucosylation of 9 with O-fucosyl trichloroacetimidate 11 as donor exhibited a dramatic increase in yield when carried out by an “inverted procedure”, i,e, the donor was added to an acceptor/catalyst solution. The obtained trisaccharide building block 12 could be readily transformed into acceptor 13 and donor 15, respectively. Thus, the dimeric hexasaccharide 16 was obtained, which was then transformed into donor 19. Its reaction with the 3′-O-unprotected lactose acceptor 20 provided the desired ocetasaccharide 21, which gave upon azido group reduction, acetylation of the amino groups, and complete O-deprotection the desired target molecule 2 characterized as its fully O-acetylated product 24.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199119910178
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Glycosylation of 2,3-diphenylindole and derivatives  -  Synthesis of O-, N-, and C-glycopyranosides (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 877-881 
    Details
    ISSN: 0170-2041
    Keywords: O-Glycosyl trichloroacetimidates ; Glycosyl bromides ; Glycopyranosyl donors ; Glycosyl acceptors, polyvalent ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of different glycosyl donors with 5-hydroxy-N-methyl-2,3-diphenylindole (1C) led only to O-glycosylation (compounds 6a-c and 8c-α,β). Depending on the O-protection of the glycosyl donors (2a-c, 3b, 4c), the β-products were obtained mainly or exclusively. The corresponding N-unsubstituted indole 1B and donors 2b and 5a, respectively, also yielded only O-glycosylated products (compounds 11b and 13a). Depending on the glycosyl donor (2a or 2c), the N-unsubstituted 5-methoxy-2,3-diphenylindole (1A) led to N- and/or C-glycosides (compounds 16a, 14a-α,β, and 14c-α,β). The structures were assigned with the help of 1H-NMR data of these products or their derivatives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1990199001164
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    Paper (German National Licenses)
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