Enantiomer-Differentiating Ability of Cyclo(L-Phe-L-Pro)₄ Having a Rigid Skeleton for Phenylalanine Methylester Hydrochloride

Abstract

The formation constant of the 1 : 1 complex of cyclo(L-Phe-L-Pro)₄ (1) with L-PheOMe·HCl was about 13.2 times that of the complex with D-PheOMe·HCl. The 1 : 1 complex of 1 with L-PheOMe·HCl formed three intermolecular hydrogen bonds between Pro² CO, Phe¹ CO and the amino group, and Phe² NH and the carbonyl group, whereas that with D-PheOMe·HCl formed only one between Phe¹ CO and the amino group.