Regioselective C‐6 Hydrolysis of MethylO‐Benzoyl‐pyranosides Catalysed byCandida RugosaLipase

Abstract

AbstractHydrolysis of six methylO‐benzoyl‐pyranosides has been investigated usingCandida rugosalipase in dioxane/buffer mixtures. The lipase catalysed the hydrolysis of all substrates in a regiospecific manner at C‐6. The rate of reaction was dependent on pyranoside structure, reaction temperature and scale, dioxane concentration and agitation speed. Starting from their C‐6O‐benzoyl precursors, the methyl 2,3,4‐tri‐O‐benzoyl‐pyranosides of α‐D‐galactose, β‐D‐galactose, α‐D‐glucose, and methyl 2,3‐di‐O‐benzoyl‐α‐D‐galactopyranoside could be isolated in 85–96 % yield. In hydrolysis of methyl 2,3,4,6‐tetra‐O‐benzoyl‐α‐D‐glucopyranoside and methyl 2,3,4,6‐tetra‐O‐benzoyl‐β‐D‐galactopyranoside substrate inhibition were observed, which in part could be overcome by increasing the reaction volume. Methyl 2,3,4,6‐tetra‐O‐benzoyl‐β‐D‐glucopyranoside and methyl 2,3,4,6‐tetra‐O‐benzoyl‐α‐D‐mannopyranoside were poor substrates forCandida rugosalipase and low degree of conversion towards products were obtained under all conditions. No acyl migration was detected in any of the products.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)