Branched-chain 2-deoxy sugars. V. Application of the Wittig reaction to methyl 3,4-O-isopropylidene-β-D-erythro-pentopyranosid-2-ulose and attempted synthesis of nucleosides of 2-deoxy-2-C-methylpentoses

Abstract

Oxidation of methyl 3,4-O-isopropylidene-β-D-arabinopyranoside (1) with ruthenium tetroxide afforded methyl 3,4-O-isopropylidene-β-D-erythro-pentopyranosid-2-ulose (2) in 78% yield. Condensation of methylenetriphenylphosphorane with 2 in the presence of H-butyllithium yielded methyl 3,4-O-isopropylidene-2-deoxy-2-C-methylene-β-D-erytho-pentopyranoside (3) in 55% yield. Reduction of the latter with 10% palladium-on-charcoal gave a 7:1 mixture of two isomeric 2-deoxy-2-C-methylpentoside derivatives in 95% yield: the preponderant product had the D-ribo configuration. The fully blocked methyl glycosides were de-isopropylidenated with methanolic hydrogen chloride to yield 6 and 7 and these were converted into the p-toluoyl esters (8) and (9). Attempts to utilize the latter in the synthesis of nucleosides of 2-deoxy-2-C-methyl pentoses were unsuccessful.