PREPARATION AND APPLICATION OF AN (S)-NAPROXEN CHIRAL STATIONARY-PHASE

A chiral stationary phase (CSP) for the liquid chromatographic separat ion of enantiomers was prepared by immobilizing the 3,5-dimethylanilid e derivative of (S)-naproxen on silica gel through the 6-methoxy-2-nap hthyl functionality of (S)-naproxen. The enantioselectivities exerted by this pi-basic CSP for resolving pi-acidic racemates were generally greater than those on the previously reported CSPs prepared by immobil izing an alkylamide of (S)-naproxen on silica gel through the alkylami de functionality. Based on the chromatographic resolution trends, two chiral recognition mechanisms are proposed. One mechanism applied for the resolution of N-(3,5-dinitrobenzoyl)-alpha-amino esters is propose d to utilize the 6-alkoxy-2-naphthyl group of the CSP as a pi-basic in teraction site for enantioselective pi-pi complexation with the 3,5-di nitrobenzoyl group of the analyte and the other mechanism is proposed to utilize the 3,5-dimethylanilide group of the CSP in resolving N-(3, 5-dinitrobenzoyl)-alpha-arylalkylamines.