The Julia-Colonna type asymmetric epoxidation reaction catalyzed by soluble oligo-L-leucines containing an alpha-aminoisobutyric acid residue: Importance of helical structure of the catalyst on asymmetric induction

Length-defined organic solvent soluble oligo-L-leucines containing an Aib r esidue were prepared by stepwise elongation and fragment condensation metho ds, and were used as catalysts in the Julia-Colonna asymmetric epoxidation reaction. The yield and enantioselectivity rose by increasing the number of amino acid units in the catalyst. The enantioselectivity was very sensitiv e to the reaction solvent. The LR characteristic bands (the amide I region) in CH2Cl2 indicated the soluble catalysts to be of helical structure in so lution.