Separation of peptide diastereomers by reversed-phase high-performance liquid chromatography and its applications : IV. New derivatization reagent for the enantiomeric analysis of α- and β-amino acids

Abstract

A new derivatization reagent, (Z- l-Val-Aib-Gly-ONSu, Z = benzyloxycarbonyl; Aib = α-aminoisobutyric acid; ONSu = N-oxysuccinimide), was developed for the enantiomeric analysis of various amino acids, including unusual α-amino acids having a long or bulky alkyl side-chain or a substituted phenyl or heteroaromatic ring and β-substituted β-amino acids. The diastereomers derived from various amino acids and this chiral reagent were well resolved by reversed-phase high-performance liquid chromatography using aqueous methanol as the eluent. As it is generally considered that in chiral derivatization for the separation of enantiomers the chiral centres in the diastereomeric derivatives should be as close as possible to each other, it is surprising that the above diastereomers, which have two chiral centres separated by nine bonds, can be well separated. This can be explained by the conformational difference between the l- l and l- d isomers.