Nucleophilic displacement reactions in carbohydrates. Part II. Reaction of 2,3:6,7-di-O-isopropylidene-5-O-toluene-p-sulphonyl-D-glycero-D-gulo-heptofuranose with sodium methoxide

Abstract

Acid-catalysed acetonation of D-glycero-D-gulo-heptose resulted in the formation of 2,3:6,7-di-O-isopropylidene-β-D-glycero-D-gulo-heptofuranose, the structure of which was established by n.m.r. spectroscopy and chemical evidence. The derived toluene-p-sulphonate was converted, by sodium methoxide, into a mixture of methyl 2,3:6,7-di-O-isopropylidene-β-D-glycero-L-talo-heptofuranoside and 1,4-anhydro-2,3:6,7-di-O-isopropylidene-α-D-glycero-D-allo-heptopyranose (1,5-anhydro-2,3:6,7-di-O-isopropylidene-β-D-glycero-D-allo-heptofuranose). The possibility of the anhydro-sugar arising by way of an intramolecular transtosylation is considered.