Matched/Mismatched Interactions in Chiral Bronsted Acid-Catalyzed Glycosylation Reactions with 2-Deoxy-Sugar Trichloroacetimidate Donors

摘要

The stereochemical outcome of glycosylation reactions of 2-deoxy-sugar trichloroacetimidates promoted by chiral BrOnsted acids is shown to be dependent on both the chirality of the catalyst and the configuration of the leaving group. High levels of selectivity (1:16 :) can be obtained with (S)-catalysts and an -trichloroacetimidate donor. Conversely, (R)-catalysts require longer reaction times and provide the product in much lower selectivity (6.6:1 :). These observations demonstrate that stereochemical match and mismatch between donor and acceptor are important factors in chiral BrOnsted acid-promoted glycosylations.