Dehydrative Glycosylation Using Heptabenzyl Derivatives of Glucobioses and Lactose

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Abstract
Dehydrative glycosylations of the 2-, 3-, 4-, and 6-OH groups of D-glucopyranose with hepta-O-benzyl derivatives of glucobioses (O-D-glucopyranosyl-(1→n)-D-glucopyranose; n = 2, 3, 4, or 6) and lactose, in the presence of a ternary mixture of p-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, and triethylamine in dichloromethane showed that the selectivity of the reaction depended on the anomeric configuration and the linking position to the reducing tribenzylglucose moiety of the nonreducing tetrabenzylglucosyl residue and on the class of the OH group to be glycosylated. The use of a quaternary mixture of p-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, N,N-dimethylacetamide, and triethylamine made all but the β(1→2)-linked biosyl donor undergo α-condensation. Several new linear trisaccharides were obtained via debenzylation of the condensates.