Oxidative hydrolysis of conformationally restrained pent-4-enyl glycosides: formation of N-acetyl-α-D-glucopyranosylamines

Abstract

The α- and β-anomers of the conformationally restrained pent-4-enyl D-glucopyranosides (5) and (6) have been synthesised, and each anomer found to give stereospecifically the corresponding N-acetyl-α-D-glucopyranosylamines (7) and (8) as the major products on treatment with N-bromosuccinimide in 1% aqueous acetonitrile. In contrast, the strain free α- and β-anomers of pent-4-enyl 2,3,4,6-tetra-O-benzyl-D-glucopyranoside (10) yield only the corresponding pyranose (11). The α-configuration of the acetamide substituent in (7) and (8) was established by derivatisation of (8) to the 4,6-di-O-acetate (12α), subsequent ¹H n.m.r. nuclear Overhauser enhancement (n.O.e.) experiments, and by independent synthesis of the 4,6-di-O-acetate-β-anomeric acetamide (12β).