Indium trichloride promoted stereoselective synthesis of O-glycosides from trialkyl orthoformates

A novel, highly stereoselective O-glycosylation method, in which orthoesters have been used as acceptors with glycals and glycosylbromides in the presence of InCl3 to afford the corresponding O-glycopyranosides in 66-95% yield, is developed. Both perbenzyl and peracetyl glycals afford the corresponding 2,3-unsaturated O-glycosides with high α-selectivity.