Chiral recognition and discrimination studies of tyrosine enantiomers on (−)-18-crown-6-tetracarboxylic acid as a chiral selector by nuclear magnetic resonance spectroscopy and docking simulations

Abstract

Considering the substantial significance of chiral biomolecules, such as amino acids, in our daily routines, we performed chiral recognition and discrimination of tyrosine (Tyr) enantiomers on (−)-(18-crown-6)-2,3,11,12-tetracarboxylic acid [(−)-18-C-6-TA] as crown-ether type chiral selector (CS) by nuclear magnetic resonance (NMR) spectroscopy and docking simulations. In this study, successful discrimination of the enantiomers of Tyr was achieved, as evidenced by the proton chemical shift differences (ΔΔδ) of Tyr enantiomers observed in the ¹H NMR spectra with (−)-18-C-6-TA CS. We compared the results of these two techniques with the findings obtained from high performance liquid chromatography (HPLC) investigations. In both NMR and HPLC experimental and docking simulation studies, a stronger interaction between the L-Tyr enantiomer with (−)-18-C-6-TA CS than the D-Tyr was consistently observed. Also, the binding energy differences (ΔΔE_L-D) found in simulation data that correspond to enantioselectivity aligned well with the NMR experimental result.