Ligand exchange HPLC technique was applied to resolve chiral separation of aliphatic side chain aminoacid racemates. Chiral selector was copper L-phenylalaninate (II) and the results showed the elution of D enantiomer followed by L form. Considering the 3-point interaction concept, a mechanism of chiral recognition was proposed, in which no change of configuration would follow the formation of pseudo-homochiral and heterochiral complexes. To prove the reliability of this mechanism, the trans configuration of homochiral complex had to be more stable than the cis form, which was confirmed by DFT-B3LYP calculation in gas phase. The infrared frequencies were also calculated and the comparison with the subtracted and deconvoluted spectrum of the in-solution complex also pointed to the presence of the trans diasteroisomer.
alpha-amino acids; L-phenylalanine; ligand exchange chromatography; ab initio molecular orbital calculations; fourier self-deconvolution
