Displacement of sugar chlorosulphates by bromide, azide, and acetate; a convenient synthesis of methyl 3,6-dideoxy-β-D-ribo-hexopyranoside

Abstract

The displacement of chlorosulphate esters by a nucleophile other than chloride is demonstrated by the synthesis of methyl 4,6-O-benzylidene-3-bromo-3-deoxy-β-D-allopyranoside from methyl 4,6-O-benzylidene-β-D-glucopyranoside 2,3-bischlorosulphate. This reaction is used as the basis for a convenient and efficient synthesis of methyl 3,6-dideoxy-β-D-ribo-hexopyranoside (paratose). Displacement of primary and secondary chlorosulphate groups has also been achieved with bromide and azide, and in one case by acetate. The reactions proceed with inversion of configuration and in some instances require the use of aprotic solvents or crown ethers.