THE BROMINATION AND HALOGENOMETHOXYLATION OF D-GLUCAL TRIACETATE

Abstract

The bromination of D-glucal triacetate gave a mixture of tri-O-acetyl-2-bromo-2-deoxyglycopyranosyl bromides containing about 60% and 30% of the compounds with the α-D-gluco and α-D-manno configurations, respectively. Reaction of the bromides with methanol in the presence of silver carbonate proceeded almost entirely with inversion of the reacting anomeric centers. Hydrogenolysis of the product of methanolysis gave methyl 2-deoxy-β-D-glucopyranoside. Reaction of D-glucal triacetate with either bromine, chlorine, or iodine in methanol containing silver acetate gave in each case about 60–65% and 35–40% yields of the corresponding methyl 2-deoxy-2-halogeno-α-D-mannopyranoside and -β-D-glucopyranoside triacetates. The mechanisms of the reactions are discussed.