The Julia-Colonna asymmetric epoxidation reaction of chalcone catalyzed bylength defined oligo-L-leucine: Importance of the N-terminal functional group and helical structure of the catalyst in the asymmetric induction

Catalysts, oligo-L-leucine, for the Julia-Colonna asymmetric epoxidation of chalcone with defined degrees of polymerization were prepared by a stepwis e elongation method. The yield and enantioselectivity in the epoxidation in creased with the degree of polymerization of the catalyst. The presence of an unprotected amine moiety at the N-terminus proved to be essential for hi gh asymmetric induction. The IR characteristic absorption bands (the amide I region) of the catalysts suggested that helical structure in the catalyst is related to asymmetric induction.