1,2-cis-Selective glucosylation enabled by halogenated benzyl protecting groups

We report on our initial results from a systematic effort to implement electron-withdrawing protecting groups and Lewis basic solvents/additives as an approach to 1,2-cis(alpha)-selective O-glucosylation. 1,2-cis-Selective O-glucosylations are reported with thioglucosides and glucosyl trichloroacetimidates and a range of acceptors. A correlation between electron-withdrawing effects and 1,2-cis selectivity has been established. This phenomenon may prove to be broadly applicable in the area of chemical O-glycosylation.