Syntheses of novel acarviosin analogs with anhydro or unsaturated sugar moieties

A new class of pseudoacarviosins with 2,3-anhydro or unsaturated sugar moieties were synthesized efficiently. The designed target disaccharides were constructed by the glycosylation reactions using 2,3-anhydromonosaccharides as glycosyl donors. The glycosylation reactions were carried out in a highly stereoselective manner in most cases, especially when the preactivation protocol was used. The anhydrosugar units of disaccharides were kept intact during the deprotection operations of protective groups. Furthermore, the disaccharides containing anhydrosugar moieties were smoothly converted to the unsaturated disaccharides via the base-promoted rearrangement of sugar epoxides.