Enantiomeric separation of d- and l-lactic acid enantiomers by use of nanotubular cyclicpeptides: A DFT study

In the present study the inclusion complexes of enantiomers of lactic acid (LA) as the guest and a series of 4, 5, 6, 7, 8 and 9 nanotubular cyclicpeptides with alanine as building block (host molecules) were investigated at the B3LYP/6-31+G(d) and CAM-B3LYP/6-31+G(d) level of theory. It was found that the most favorable complex is formed between CyAla9 and enantiomers of lactic acid. The ability of cyclic peptides as a potential tool for separation of enantiomers of lactic acid was examined. Geometrical changes of lactic acid due to complexation and hydrogen bonding were calculated. The NBO calculations for analyzing the nature of the intermolecular hydrogen bonds were performed. This study can provides theoretical support for experimental work on more complex systems.