LIPASE-CATALYZED REGIOSELECTIVE ACYLATION AND DEACYLATION OF GLUCOSE DERIVATIVES

In the development of an efficient synthesis of 1-O-decanoyl-2,3,4,6-tetra-O-acetyl beta-D-glucose (beta-2) several lipase-based approaches have been explored. Among five immobilized lipases tested, the lipase from Candida antarctica proved particularly efficient for catalyzing selective hydrolysis in the 1-position of 1,2,3,4,6-penta-O-acetyl-beta-D-glucose (beta-1). Using triethylamine as catalyst, the hydrolysis product 2,3,4,6-tetra-O-acetyl-D-glucose (3) can be esterified with decanoyl chloride to form beta-2 selectively, thereby providing an efficient chemo-enzymatic synthesis starting from readily available raw materials. Attempts to produce beta-2 from beta-1 by lipase-catalyzed interesterification or to esterify 3 with decanoic acid using a lipase as catalyst were unsuccessful. The latter finding was explained by the hemiacetal OH group of glucose being unable to act as nucleophile in the lysis of the lipase acyl-enzyme intermediate. Furthermore, beta-2 was found to bee a too bulky substrate to fit into the active site of any of the lipases tested.