Enzyme‐Mediated Regioselective Acylations of Flavonoid Disaccharide Monoglycosides

Flavonoid disaccharide monoglycosides have been acylated by the catalytic action of the protease subtilisin in anhydrous pyridine. The effects of the nature of the sugars and of the interglycosidic bonds on the regioselectivity of the reactions have been analyzed. The selectivity was excellent with rutin (1), hesperidin (2), naringin (6), and quercetin 3‐O‐[O‐(β‐D‐glucopyranosyl)‐(1→4)‐α‐L‐rhamnoside] (9), giving single monoesters on their glucose moieties (see la, 2a, 6a, and 9b, resp.); quite interestingly, in the last compound, acylation did not occur at the free primary OH group but at the secondary OHC(3‴). On the other hand, a mixture of mono‐ and diesters was obtained with the flavonoid peltatoside (7).