Synthesis of the nucleoside antibiotic formycin B

Abstract

Curtius rearrangement of the 4-azide of 5-(tri-O-benzyl-β-D-ribofuranosyl)pyrazole-3,4-dicarboxylic acid gave the N-carboxy-anhydride of the 4-amino-3-acid the methyl ester of which, on heating in formamide followed by catalytic hydrogenolysis, gave formycin B.