Glycosyl trichloroacetimidates trisaccharide synthesis using

Scheme 5. Synthesis of trisaccharide using glycosyl trichloroacetimidates and glycosyl phosphates.

A convergent synthesis of the pentasaccharide derivative 33 of the triterpeniod saponin obtained from the plant Spergularia ramosa was achieved as outlined in Scheme 6 68 The entire assembly relied on use of the trichloroacetimidate protocol and was accomplished in a three plus two fashion. The assembly of the trisaccharide was initiated by the glycosidation of glucosyl trichloroacetimidate donor 22 with rhamnosyl diol acceptor 23 to provide disaccharide 24 in 63% yield. The latter could be used directly as the glycosyl acceptor for the reaction with xylosyl donor 25, leading... 

Studies of the synthesis of olivomycin A have been reported [183], Glycosylation of a glycal acceptor with a trichloroacetimidate and an acetate donor gave a trisaccharide which was transformed into the trichloroacetimidate and used for the glycosylation of the acyloin acceptor. The resulting p-glycoside is a model compound for the approach to the synthesis of olivomycin A. 

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