Enantiomer separation of α-amino acid methyl esters and some aliphatic amines as 9-anthraldimine derivatives by high performance liquid chromatography

Abstract

The liquid chromatographic enantiomer separation of several alpha-amino acid methyl esters as 9-anthraldehyde Schiff base derivatives on five polysaccharide-derived chiral stationary phases (CSPs) was described. The 9-anthraldehyde imine derivatives of a-amino acid esters were prepared by stirring 9-anthraldehyde with the alpha-amino acid ester hydrochloride salts. The chromatographic conditions were 3%-10% (v/v) 2-propanol-n-hexane as the mobile phases at the flow rate of 1.0 mL/min and detected at UV 254 nm. The performance of Chiralcel OD (or Chiralcel OD-H) among the five CSPs was superior to those of the other CSPs for the resolution of 9-anthraldimine derivatives of alpha-amino acid methyl esters. The enantiomers of all a-amino acid methyl esters as the 9-anthraldimine derivatives were base-line resolved on Chiralcel OD or Chiralcel OD-H (alpha = 1.24-5.47, Rs = 2.56-13.90). The L-enantiomers of all analytes were strongerly restrained than the respective D-enantiomers on the Chiralcel OD (or Chiralcel OD-H) CSPs. The method was also used for the enantiomer separation of aliphatic amines and good separation was obtained. It is expected that the analytical method will be useful for the enantiomer resolution of other alpha-amino acid esters and amine compounds as 9-anthraldimine derivatives.