SYNTHESIS OF BETA-D-TALOPYRANOSIDES AND BETA-D-MANNOPYRANOSIDES VIA INTRAMOLECULAR NUCLEOPHILIC-SUBSTITUTION

The selective and efficient syntheses of beta-D-talopyranosides and be ta-D-mannopyranosides were achieved from beta-D-galactopyranosides and beta-D-glucopyranosides, respectively, that carry a benzoyl group at O-3 and a triflyl group at O-2. The transformation was performed in th e presence of an alcohol via intramolecular nucleophilic attack of the benzoyl group with inversion of configuration at C-2 that provided, f irst, the formation of the corresponding 2,3-(alkyl orthobenzoates) of the desired beta-D-talopyranosides or beta-D-mannopyranosides, follow ed by acidic opening of the cyclic orthoesters.