Complementary and Synergistic Roles in Enzyme-Catalyzed Regioselective and Complete Hydrolytic Deprotection of O-Acetylated β-d-Glucopyranosides of N-Arylacetohydroxamic Acids

An efficient chemoenzymatic synthesis of β-d-glucopyranosides of N-arylacetohydroxamic acids 3a–c was achieved by the chemoselective O-deacetylation of 1a–c under mild, neutral conditions, with no accompanying N-deacetylation. Lipase AS Amano from Aspergillus niger (LAS) and carboxylesterase from Streptomyces rochei (CSR) played complementary, synergistic roles in the O-deacetylation of 1a and its partially O-deacetylated intermediates. An intramolecular O-acetyl migration, which proceeded simultaneously, also accelerated the overall reaction rate. Under weakly acidic conditions at pH 5.0, where the intramolecular O-acetyl migration is markedly slower, LAS, CSR, and porcine liver esterase (PLE) exhibited different regioselective O-deacetylation activities. LAS and PLE showed regioselective 3-O-deacetylation and 2-O-deacetylation activity, respectively, for 1a and its tri-O-acetyl derivatives (4-7). CSR showed marked preferences for 3-O-deacetylation of 2,3,6-tri-O-acetyl intermediate 5 and 4-O-deacetylation of 2,4,6-tri-O-acetyl intermediate 6. In contrast, CSR showed almost no O-deacetylation activity toward the other tri-O-acetyl intermediates 4 and 7, which were efficiently O-deacetylated by LAS in a complementary manner. Using these enzyme-catalyzed regioselective O-deacetylation as well as chemical methods, we could synthesize all 14 partially O-acetylated intermediates (4–17) derived from 1a.