Synthetic studies with carbonates. Part 11. D-Glucopyranose 1-carbonate derivatives; pyrolytic behaviour and use for glucosylation of phenols

Abstract

2,3,4,6-Tetra-O-acetyl-1-O-phenoxycarbonyl-β-D-glucopyranose (1), its 1-O-methoxycarbonyl analogue (3), and 2,3,4,6-tetra-O-benzoyl-1-O-phenoxycarbonyl-β-D-glucopyranose (5) underwent pyrolysis to give mixtures of various products whose composition depended on the structure of the starting material. However, the α-anomers of (1) and (3) were not susceptible to pyrolysis, even under more drastic conditions. Glucosylation reactions of phenols with the β-D-glucopyranose 1-carbonates were conducted autocatalytically to give the corresponding phenyl β-D-glucopyranoside derivatives in moderate yields. Especially useful was the synthesis of o-nitrophenyl and o-chlorophenyl glucopyranoside derivatives, which cannot be prepared through the Helferich's procedure, even under acid-catalysis conditions. A reaction mechanism involving an orthoester intermediate is suggested; such an intermediate was isolated and transformed into the corresponding glucopyranoside derivatives etc.