A Traceless Directing Group Enables Catalytic SN2 Glycosylation toward 1,2-cis-Glycopyranosides

Generally applicable and stereoselective formation of 1,2-cis-glycopyranosidic linkage remains a long sought after yet unmet goal in carbohydrate chemistry. This work advances a strategy to this challenge via stereoinversion at the anomeric position of 1,2-trans glycosyl ester donors. This S(N)2 glycosylation is enabled under gold catalysis by an oxazole-based directing group optimally tethered to a leaving group and achieved under mild catalytic conditions, in mostly excellent yields, and with good to outstanding selectivities. The strategy is also applied to the synthesis of oligosaccharides.

Automated summary

This study introduces a strategy for the formation of 1,2-cis-glycosidic linkage using gold catalysis, achieving excellent yields and outstanding selectivities under mild conditions. This strategy is also successfully applied to the synthesis of oligosaccharides.