Original enzyme-catalyzed synthesis of chalcones: utilization of hydrolase promiscuity
An E-chalcone was obtained with very high stereoselectivity for the first time by an enzyme-catalyzed Claisen-Schmidt condensation between benzaldehyde and acetophenone. From a set of lipases, only that from hog pancreas demonstrated promiscuity, catalyzing the reaction in the presence of imidazole as a promoter. Another enzyme, acylase from Aspergillus melleus (EC 188.8.131.52) also proved to be active in the synthesis of E-chalcone under the same reaction conditions. This acylase along with the recombinant D-aminoacylase (EC 184.108.40.206) also catalyzed the reaction between acetophenone and p-nitrobenzaldehyde. Such a "green" approach to the synthesis of chalcones is of great interest because of the important applications of chalcones as formula ingredients in the pharmaceutical, food and cosmetic industries.