Polyamino acids as synthetic enzymes: mechanism, applications and relevanceto prebiotic catalysis

Abstract

Polyamino acids, such as polyleucine, behave as synthetic enzymes in the asymmetric epoxidation of chalcone and other electrondeficient alkenes (the JuliaColonna reaction). The influences of reaction conditions, of the molecular structure of the catalysts and of the scalingup of the process on the enantioselectivity of the reaction have been determined. The kinetics and mechanism have been investigated using a soluble PEGpolyleucine conjugate, which behaves in a similar way to an enzyme, showing saturation kinetics for both chalcone and HOO. Enantioselective catalysis is achieved with peptides with as few as five residues and scalemic catalysts show high chiral amplification. Here, we discuss the relevance of theseenzyme like catalysts to prebiotic processes, such as the role of small peptides in the formation of optically active cyanohydrins.