Boronic acid-catalyzed regioselective Koenigs-Knorr-type glycosylation is presented. The reaction of an unprotected or partially protected glycosyl acceptor with a glycosyl halide donor in the presence of silver oxide and a low catalytic amount of imidazole-containing boronic acid was found to proceed smoothly, which enables construction of a 1,2- glycosidic linkage with high regioselectivities. This is the first example of the use of a boronic acid catalyst to initiate regioselective glycosylation via the activation of -vicinal diols in glycosyl acceptors.
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