SYNTHESIS OF THE METHYL 3-AMINO-3-DEOXY-ALPHA-D-ALLOPYRANOSIDE AND BETA-D-ALLOPYRANOSIDE AND BETA-D-ALLOFURANOSIDES

Methyl 3-amino-3-deoxy-alpha-D-allopyranoside was synthesized from methyl 2-O-benzoyl-4,6-O-benzylidene-alpha-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-alpha-D-glucofuranose 3-triflate afforded the corresponding 3-azido-3-deoxy-alpha-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-beta- and alpha-D-allopyranosides and the corresponding beta-D-allofuranoside, with a 3:1 pyranoside to furanoside ratio; the two amino beta-glycosides were then obtained by catalytic hydrogenation. Methanolysis of the 3-acetamido-3-deoxy-alpha-D-allofuranose diacetal produced a glycoside mixture composed mainly of methyl 3-amino-3-deoxy-beta- and -alpha-D-allofuranosides in a 2:1 ratio, together with only small proportions of the pyranosidic isomers.