Characterization of chemo- and regioselectivity in enzyme-catalyzed consecutive hydrolytic deprotection of methyl acetyl derivatives of 1-β-O-acyl glucuronides

Methyl acetyl derivatives of 1-β-O-(o-, m-, or p-phenyl)benzoyl glucuronides 2a–c are fully deprotected by a one-pot consecutive enzyme-catalyzed hydrolytic reaction to afford 4a–c, without isolation of the O-deacetylated derivatives 3a–c. A lipase AS Amano from Aspergillus niger (LAS) and a carboxylesterase from Streptomyces rochei (CSR) showed high chemoselectivity toward the O-deacetylation of the o- and m-isomers, respectively. Chemoselective O-deacetylation of the p-isomer was promoted only in the presence of both enzymes. A lipase type B from Candida antarctica (CALB) was effective for the subsequent enzymatic hydrolysis of the methyl esters of 3a–c. LAS exhibited also regioselective 3-O-deacetylation activity to afford the corresponding 2,4-di-O-acetyl intermediates 5a–c, for which CSR showed higher O-deacetylation activity than that for 2a–c. In kinetic studies using p-nitrophenyl ester substrates, LAS exhibited a broader acyl preference, the octanoyl ester being most effectively hydrolysed, whereas CSR exhibited the highest hydrolytic activity toward the acetyl ester. LAS and CSR play complementary as well as synergistic roles in the O-deacetylation of 2 bearing R groups of different steric bulkiness.