STUDIES ON THE ENZYMATIC ACYLATION OF QUINIC ACID, SHIKIMIC ACID, AND THEIR DERIVATIVES IN ORGANIC-SOLVENTS

Quinic acid (1a), shikimic acid (2), and their derivatives were acylated in organic solvents by several lipases and by the protease subtilisin Carlsberg. The most satisfactory results were obtained with methyl (or benzyl) quinate (7a (or 8a)) and lipase from Chromobacterium viscosum adsorbed on Celite, which showed an overwhelming preference towards the acylation of OH-C(4). Under optimized conditions, the synthetically useful 4-O-acetylquinate 8d was isolated in ca. 90% yield. On the other hand, acylation of methyl shikimate (10a) showed no regioselectivity with any of the enzymes tested. A possible rationale for the different behavior of Chromobacterium viscosum lipase towards 7a and 10a is given, comparing the conformations of these two molecules, as deduced from H-1-NMR and molecular-mechanics calculation.