Synthesis of benzyl 6- O-benzoyl-3,4- O-isopropylidene-β- D-galactopyranoside and of 2- O-α- L-fucopyranosyl- D-galactose

Abstract

Benzyl β- D-galactopyranoside was converted into the crystalline 3,4- O-isopropylidene derivative ( 2), which was selectively benzoylated to give crystalline benzyl 6- O-benzoyl-3,4- O-isopropylidene-β- D-galactopyranoside ( 8. The structure of 8 was established by various reactions, which included the preparation of benzyl 6- O-benzoyl-β- D-galactopyranoside ( 9) and of benzyl 2- O-benzoyl-β- D-galactopyranoside ( 10). Condensation of 8 with 2,3,4-tri- O-acetyl-α- L-fucopyranosyl bromide, followed by removal of the isopropylidene benzoyl and acetate groups, afforded crystalline benzyl 2- O-α- L-fucopyranosyl-β- D-galactopyranoside ( 12). Catalytic hydrogenolysis of 12 gave the disaccharide 2- O-α- L-fucopyranosyl- D-galactose ( 1), which was identical with the natural product.