Chiral Catalyst-Directed Dynamic Kinetic Diastereoselective Acylation of Anomeric Hydroxyl Groups and a Controlled Reduction of the Glycosyl Ester Products.

A catalytic method is developed for the diastereoselective acylation of the anomeric hydroxyl group in diverse carbohydrates to form either α- or β-anomeric esters. While exclusive formation of the β-isomer was observed in most sugar substrates with one enantiomer of the chiral catalyst, moderate to high α-selectivity was obtained by using the other enantiomer of the chiral catalyst. The resulting α- and β-anomeric esters have very different reactivity toward a reduction reaction.