Total synthesis of higher-carbon sugars: Synthesis of methyl 3,4,5-tri- O-acetyl-1,7-di- O-benzyl-α- dl- gluco-Hept-2-ulopyranoside

Abstract

2-(2-Benzyloxy-1-hydroxyethyl)-5-benzyloxymethylfuran [obtained by the reaction of 2-benzyloxymethylfuran with butyl glyoxylate, reduction of the resulting hydroxyester with lithium aluminium hydride, followed by benzylation of the primary hydroxyl group] was converted into methyl 1,7-di- O-benzyl-3,4-dideoxy-α-and -β- dl-hept-3-en-2-ulopyranosid-5-uloses. Carbonyl-reduction of the uloses and inversion of configuration at C-5 in the resulting alcohols afforded four stereoisomeric 3,4-unsaturated methyl hept-2-ulosides. Epoxidation of the α- erythro isomer, ring-opening of the resulting oxirane, and then acetylation yielded the title compound.