Diastereoselective free-radical reactions. Part 3. The methyl glucopyranos-1-yl and the 1,2-O-isopropylideneglucopyranos-1-yl radicals: conformational effects on diastereoselectivity

Abstract

The 3,4,6-tri-O-benzyl-2-O-t-butyldimethylsilyi-1-O-methyl-D-glucopyranos-1-yl and the 3,4,6-tri-O-benzyl-1,2-O-isopropylidene-D-glucopyranos-1-yl radicals are quenched with high selectivity (> 25 : 1) from the α- and β-face, respectively, by t-dodecanethiol. The reasons for this selectivity are discussed and the preparation of the radical precursors is presented. An improved preparation of 3,4,6-tri-O-benzyl-D-glucopyranose is described.