Nuclear magnetic resonance studies for the chiral recognition of the novel chiral stationary phase derived from 18-crown-6 tetracarboxylic acid

Enantioselectivities observed in high-performance liquid chromatography (HPLC) with the novel chiral stationary phase (CSP-18C6I) derived from (+)-18-crown-6 tetracarboxylic acid (18C6H(4)) were investigated by using nuclear magnetic resonance (NMR) spectrometry. The elution orders in CSP-18C6I, that is, the S-enantiomer of 1-(1-naphthyl)ethylamine (1-NEA) and the L-enantiomer (S-form) of alanine-beta-naphthylamide (Ala-beta-NA) eluted prior to each corresponding enantiomer, were successfully explained on the basis of the apparent binding constants (K-a) of the enantiomers to the CSP moiety which were calculated from H-1-NMR experiments. Detailed HPLC and NMR studies for the chiral recognition of racemic amino compounds with 18C6H(4) hosts showed that H-1-NMR spectrometry is a useful technique for the investigation of the chiral recognition mechanism in HPLC. Additionally, it was found 18C6H(4) can be recommended as a useful chiral shift reagent for the enantiomeric excess determination by H-1-NMR. (C) 1998 Elsevier Science B.V. All rights reserved.