SCREENING AND CHARACTERIZATION OF BIOCATALYSTS FOR SYNTHESIS OF WIELAND MIESCHER KETONE: A VERSATILE SYNTHETIC INTERMEDIATE

Abstract

Biocatalysts derived from biological molecules such as proteins, RNA, and DNA have long been exploited for applications in synthetic chemistry. Lipases, a versatile class of biocatalysts, are known to exhibit significant promiscuity for non-native substrates in non-aqueous and mixed organic/aqueous solvents. While lipases are known to possess catalytic activity for a wide range of organic transformations, predicting which lipases will catalyze specific carbon-carbon bond forming reactions remains a significant challenge. In this study, the catalytic potential of a library of commercially available lipases was investigated by screening them for catalysis of the Robinson Annulation, a synthetically important carbon-carbon bond forming reaction. Specifically, the lipase library was screened for synthesis of the Wieland-Miescher Ketone, an important intermediate in the synthesis of biologically active compounds such as steroids and terpenoids, from methyl vinyl ketone and 2-methyl-1,3-cyclohexanedione. An optimized procedure is presented for Wieland-Miescher Ketone synthesis using a crude preparation of porcine pancreatic lipase (PPL), reporting on both yield and enantiomeric excess. Finally, commercially available lipases are often sold as crude preparations, containing many different proteins, and are often used by many researchers without further purification, potentially obscuring the identity of the catalytic species. Therefore, a methodology to isolate and characterize the active component(s) of these lipase formulations is described in this study.