Enantiomer separation and molecular recognition with new chiral stationary phases on 4-chloro-3,5-dinitrobenzoic acid amides of alpha,beta-aminoalcohols and alpha-arylethylamines

Amides of 4-chloro-3,5-dinitrobenzoic acid (1) (CDNB) with enantiomerically pure alpha,beta-aminoalcohols (2-5) and alpha-substituted ethylamines,([6-9]) have been prepared as chiral selectors 10-17 and bound to aminopropyl silica gel affording chiral stationary phases CSPs 1-8. Comparative tests of their separation efficacy for 32 racemic analytes, representative of race-mates with selected functionalities, has revealed important contribution of the pi-acidic branching unit, the amide of 3,5-dinitro-4-alkylaminobenzoic acid, but limited contribution of both, hydrophilic hydroxy groups in the CSPs 1-4 and pi-basic aromatic units in the CSPs 6-8. Contribution to enantioselection efficacy of the gamma-aminopropyl groups on the silica surface, in the vicinity to the chiral selector, is documented comparing the efficacy of CSP 8 and CSP 8'.