Kinetic resolution of rac-phenylalanine by stereoselective complexation to a chiral cobalt complex through pi-pi stacking interaction.
A cobalt(III) complex with chiral ligand, H2cpel (N-carboxymethyl-N-pyridylethyl-l-leucine), was prepared for chiral recognition of amino acids. Through the competitive coordination of racemic phenylalanine to the chiral cobalt complex, [Co(cpel)(CO(3))](-) (1), enantioselective recognition was achieved on the ternary complex, which was determined on the basis of HPLC analysis with a chiral column. The formation rate for the [Co(cpel)(l-phe)] complex (2) was 6-times superior to that of [Co(cpel)(d-phe)] (3). The preferential formation of 2 might be illustrated by the interligand pi-pi stacking interaction. Crystal structural analysis for 2 and 3 revealed that aromatic rings, pyridine ring of CPEL and phenylalanine sidechain, in 2 were very close each other but those in 3 were far apart. Such interligand aromatic interaction in 2 was also examined by the use of (1)H NMR spectra.
D003035:Cobalt / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D010649:Phenylalanine / Q000737:chemistry*; D013237:Stereoisomerism; D014961:X-Ray Diffraction
D003035:Cobalt; D010649:Phenylalanine