CHEMOSELECTIVE GLYCOSYLATIONS .2. DIFFERENCES IN SIZE OF ANOMERIC LEAVING GROUPS CAN BE EXPLOITED IN CHEMOSELECTIVE GLYCOSYLATIONS

We have developed a novel chemoselective glycosylation strategy. This glycosylation strategy is based on the fact that the glycosyl reactivi ty of an anomeric thiol group can be controlled by the bulkiness of th is group whereby we have produced a new range of differentially reacti ve coupling substrates. It was also shown that the anomeric configurat ion of the thioglycosides affects the reactivity of the substrates. Th e new approach will enable complex oligosaccharides of biological impo rtance to be prepared in a highly convergent manner. The versatility o f this approach is demonstrated by the synthesis of pentasaccharide 34 from the building blocks 7, 9, 10, 12, and 14 without a single protec ting group manipulation.