Lipase-catalyzed highly regioselective synthesis of acylated chlorogenic acid

Abstract

A highly efficient regioselective acylation of chlorogenic acid in methyl tert-butyl ether was developed in this study. The effects of the solvent, enzyme type, temperature, enzyme dosage, molar ratio of the substrate, reaction time, and acyl donor on the acylation and the regioselectivity of chlorogenic acid were investigated. Lipozyme RM, an alternative enzyme to Novozym 435, is more economical and suitable for catalyzing the acylation of chlorogenic acid. Using vinyl butyrate as the acyl donor, the conversion rate of chlorogenic acid reached 59.6% and 4-O-mono substitution accounted for 89.6% under the optimum conditions (temperature, 55 °C; molar ratio of CA to acyl donor, 1:10; speed of agitation, 400 rpm) after 7 days of reaction. The medium chain fatty acid vinyl ester is a more suitable acyl donor. When vinyl octanoate was used as the acyl donor, the conversion rate of chlorogenic acid reached 46.0% after 2 days of reaction. However, when vinyl laurate was used as the acyl donor, the product was only substituted at the 4-O-mono position and the regioselectivity was highly improved.