Synthesis of the methyl 3-amino-3-deoxy-α- and β- d-allopyranosides and -allofuranosides

Abstract

Methyl 3-amino-3-deoxy-α- d-allopyranoside was synthesized from methyl 2- O-benzoyl-4,6- O-benzylidene-α- d-glucopyranoside in a 5-step sequence involving trifluoromethylsulfonylation, azide displacement, deprotection, and catalytic hydrogenation. On displacement with tetramethylguanidinium azide, 1,2:5,6-di- O-isopropylidene-α- d-glucofuranose 3-triflate afforded the corresponding 3-azido-3-deoxy-α- d-allofuranose diacetal, which was converted into the 3-amino and 3-acetamido products. Acid-catalyzed methanolysis of the azido diacetal gave methyl 3-azido-3-deoxy-β- and -α- d-allopyranosides and the corresponding β- d-allofuranoside, with a 3:1 pyranoside to furanoside ratio; the two amino β-glycosides were then obtained by catalytic hydrogenation. Methanolysis of the 3-acetamido-3-deoxy-α- d-allofuranose diacetal produced a glycoside mixture composed mainly of methyl 3-amino-3-deoxy-β- and -α- d-allofuranosides in a 2:1 ratio, together with only small proportions of the pyranosidic isomers.