Synthetic approaches to 6-substituted 9-(3-azido-3,4-dideoxy-β-d,l-erythro-pentopyranosyl)purines

Abstract Methyl 3-azido-2- O -benzoyl-3,4-dideoxy-β- dl - erythro -pentopyranoside ( 6 ) was synthesized through two routes in five steps from methyl 2,3-anhydro-4-deoxy-β- dl - erythro -pentopyranoside ( 1 ). The first route proceeded via selective azide displacement of the 3-tosyloxy group of methyl 4-deoxy-2,3-di- O -tosyl-α- dl - threo -pentopyranoside, followed by detosylation and benzoylation. The second route consisted, with a better overall yield, in the azide displacement of the mesyloxy group of methyl O -benzoyl-4-deoxy-3- O -methylsulfonyl-α- dl - threo -pentopyranoside ( 10 ), obtained by benzylate opening of 1 , followed by benzoylation, debenzylation, and mesylation. Compound 6 was transformed into its glycosyl chloride, further treated by 6-chloropurine to give the nucleoside 9-(3-azido-2- O -benzoyl-3,4-dideoxy-β- dl - erythro -pentopyranosyl)-6-chloropurine ( 13 ). When treated with propanolic ammonia, 13 yielded 9-(3-azido-3,4-dideoxy-β- dl - erythro -pentopyranosyl)adenine.