Ferric chloride: a mild and versatile reagent for the formation of 1,6-anhydro glucopyranoses

Abstract A novel method for the preparation of 1,6-anhydro glucopyranoses (mono- and disaccharides) utilizing anhydrous FeCl 3 as Lewis acid is described. Treatment of methyl 6- O -benzyl and 6- O - p -methoxybenzyl-α/β d -glucopyranosides derivatives with FeCl 3 in CH 2 Cl 2 at room temperature and 40°C afforded 1,6-anhydro glucopyranosides in moderate to good yields, through a debenzylation and intramolecular glycosidation in one step. A plausible reaction pathway is proposed.