Crystallographic studies for the chiral recognition of the novel chiral stationary phase derived from (+)-(R)-18-crown-6 tetracarboxylic acid

Chiral discrimination observed in high-performance liquid chromatography (H PLC) with the novel chiral stationary phase (CSP-18C6I) derived from (+)-(R )-18-crown-6 tetracarboxylic acid [(+)-18C6H(4)] was investigated by X-ray crystallographic analysis of the complex composed of the R-enantiomer of 1- (1-naphthyl) ethylamine (1-NEA) and (+)-18C6H(4). Mixtures of 1-NEA (the R- or S-enantiomer) and (+)-18C6H(4) were dissolved in methanol-water (1:1) s olution and allowed to stand for crystallization. The R-enantiomer crystall ized with (+)-18C6H(4) as a co-crystal, although the S-enantiomer did not. This result was in good agreement with the enantiomer elution order of 1-NE A in CSP-18C6I. The apparent binding constants (K-a) of the enantiomers to the (+)-18C6H(4) obtained from H-1-NMR experiments also supported the above -mentioned result. The X-ray crystal structure of the 1:1 complex of the R- enantiomer and (+)-18C6H(4) indicated the four sets of hydrogen bond associ ation between the naphthylethylammonium cation and oxygen of polyether ring or carbonyl group of (+)-18C6H(4). Chirality 11:173-178, 1999. (C) 1999 Wi ley-Liss, Inc.