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 (1H-NMR) analysis was investigated. In general, amino compounds having an aromatic ring were well chiral recognized with 18C6H(4) compared with those having no aromatic ring. Effects of 18C6H(4) concentration and the kind of deuterated solvents (D(2)O, CD(3)OD and CD(3)CN) 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 (D(2)O, CD(3)OD or CD(3)CN) 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 1H-NMR employing 18C6H(4) as a chiral shift reagent.