PIG-LIVER ESTERASE CATALYZED-HYDROLYSIS OF METHYL 2,3-DI-O-ACETYL-5-DEOXY-ALPHA-D-ARABINOFURANOSIDES AND 2,3-DI-O-ACETYL-5-DEOXY-BETA-D-ARABINOFURANOSIDES

The regioselectivity of a pig liver esterase (PLE) catalyzed hydrolysi s of methyl 2,3-di-O-acetyl-5-deoxy-alpha-D-arabinofuranoside (1) and methyl 2,3-di-O-acetyl-5-deoxy-beta-D-arabinofuranoside (2) was establ ished by GLC. Diacetate 1 gave exclusively methyl 3-O-acetyl-5-deoxy-a lpha-D-arabinofuranoside while diacetate 2 produced both methyl 2-O-ac etyl-5-deoxy-beta-D-arabinofuranoside and methyl 3-O-acetyl-5-deoxy-be ta-D-arabinofuranoside which were resistant to subsequent hydrolysis. The Michaelis constants and maximal velocities were determined for 1 a nd 2. The first-order rate constants were computed for 1, 2, and all c orresponding monoacetates. The results were evaluated on the basis of a Jones's active-site model for PLE and the additional criteria valid for acetyl eaters of pentofuranosides were proposed.