Abstract
Liquid chromatographic separation of the enantiomers of some α-amino acids as π-acidic N-3,5-dinitrobenzoyl (DNB) derivatives has been investigated on two π-acidic chiral stationary phases (CSPs) derived from (L)-DNB leucine. Chromatographic study of the resolution of a homologous series of DNB leucine derivatives was performed on a secondary amide linked CSP 1 and a tertiary amide double-tethered CSP 2. The enantioselectivities in all analytes of DNB leucine derivatives on CSP 2 are substantially greater than those afforded by CSP 1. The enantioselectivities of tertiary dialkylamides of DNB leucine show the greatest on CSP 2 with a tertiary amide tether. It is noteworthy that the (L)-enantiomers of all investigated analytes of DNB leucine derivatives were preferentially retained on (L)-DNB leucine derived CSP 1 and CSP 2. Based on chromatographic results of the resolution of DNB leucine derivatives on CSP 1 and CSP 2, a plausible chiral recognition mechanism is described.