Evaluation of new chiral stationary phases of bonded cyanuric chloride with amino acid and naphthylalkylamine substituents for liquid chromatographic separation of amino acids and amino alcohols as dinitrobenzoyl derivatives

Abstract

Chiral stationary phases (CSPs) with two chiral centers derived from ( R S )- phenylalanyl- and ( S)-1-(1-naphthyl)ethylamino-disubstituted cyanuric chloride and the corresponding stationary phases containing one chiral center, by replacing a substituent group attached to the asymmetric center with hydrogen, were prepared for evaluating the enantioseparation of amino acid and amino alcohols as dinitrobenzoyl derivatives. Chiral stationary phases derived from ( R)-alanyl- and ( S)-1-(1-naphthyl)ethylamino-disubstituted cyanuric chloride were prepared for comparison. The phase (CSP-1) with two chiral centers provides barely satisfactory recognition ability to separate the enantiomers of dinitrobenzoyl (DNB) derivatives of amino acid methyl esters and amino alcohols by high-performance liquid chromatography (HPLC). The chromatographic results show that for a CSP bearing two chiral centers the phenylalanyl moiety dominates the chiral recognition and that the alteration of the absolute configuration of the phenylalanyl moiety from ( R)- to ( S)-configuration would worsen or even diminish the enantioseparation. The phenyl ring in the phenylalanyl moiety of the CSP seems to exert steric effects instead of acting as a π-interacting group in chiral recognition. Mechanisms for chiral recognition in liquid chromatography are discussed.