REGIOSELECTIVE ACYLATION OF POLYHYDROXYLATED NATURAL COMPOUNDS CATALYZED BY CANDIDA-ANTARCTICA LIPASE-B (NOVOZYM-435) IN ORGANIC-SOLVENTS

A systematic investigation on the transesterification activity and reg ioselectivity of the immobilized lipase B from Candida antarctica (Nov ozym 435) has been performed. This enzyme has been found to be quite a ctive in such solvents as THF, acetone, dioxane, and in mixtures of th ese solvents with pyridine. Several glycopyranosides have been acetyla ted, showing that the regioselectivity displayed by Novozym 435 toward s sugar secondary OH's is deeply influenced by the nature of the aglyc one and by the stereochemistry of the glycosidic bond. This informatio n on the regioselectivity of the lipase has been exploited for the pre paration of acetyl derivatives of flavonoid glycosides.