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Abstract

Broadly applicable and stereoselective formation of glycosidic linkage remains challenging yet of critical importance in giycoscience. By developing an SN2 glycosylation, this work advances a general solution to this challenge via stereoinversion at the anomeric position of glycosyl ester donors. This SN2 process is enabled by a basic directing-group in the leaving-group, which is activated by a cationic gold catalyst or any other electrophilic reagent. Unlike all the reported directing group approaches, this strategy is applicable to any glycosyl donors—a long sought-after yet unmet goal in carbohydrate chemistry; moreover, the basic directing-group upon glycosylation is lost as part of the leaving-group and hence traceless in the glycoside products, therefore avoiding potential complications in downstream transformations. Highly selective construction of glycosidic bonds including challenging 1,2-cis glycosidic bonds is achieved in excellent yields. The strategy is applied iteratively to access oligosaccharides and can distinguish alcohols with different steric hindrance.

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First Claim