Nuclear magnetic resonance studies for the chiral recognition of (+)-(R)-18-crown-6-tetracarboxylic acid to amino compounds

Chiral recognition capability of (+)-(R)-18-crown-6-tetracarboxylic acid (18C6H(4)) to various amino compounds containing 16 amino acids, five alkyl amines, seven aminoalcohols and other amino compounds in nuclear magnetic resonance (H-1-NMR) analysis was investigated. In general, amino compounds having an aromatic ring were well chiral recognized with 18C6H4 compared with those having no aromatic ring. Effects of 18C6H(4) concentration and the kind of deuterated solvents (D2O, CD3OD and CD3CN) for measurement on the chiral recognition was investigated in detail. Concentration of 5 equivalent 18C6H(4) to the amino compounds was found to be sufficient for the chiral recognition. On the other hand, an effective deuterated solvent (D2O, CD3OD or CD3CN) for measurement was different in each compound. Distinguishment of 1.0% of the minor enantiomer (D-form) in L-alanine-beta-naphthylamide was found to be possible by H-1-NMR employing 18C6H(4) as a chiral shift reagent. (C) 2002 Elsevier Science B.V. All rights reserved.