Self-disproportionation of enantiomers via achiral gravity-driven column chromatography: A case study of N-acyl-α-phenylethylamines

Abstract

Herein we report a study of the self-disproportionation of enantiomers (SDE) via gravity-driven achiral column chromatography of a series of amides derived from 1-phenylethylamine. We demonstrated that structural and electronic factors of the substituents play an important role in the observed magnitude of the SDE. For the first time, the SDE phenomenon of amides with that of thioamides was compared. We demonstrate that, in sharp contrast to amides, the substitution of the sulphur atom for the oxygen in the acyl group, strongly reduced the observed magnitude of the SDE. These results clearly indicate the importance of the hydrogen bonding for the formation of homo/hetero-chiral association responsible for manifestation of the SDE phenomenon.

Keywords: Amide bond; Enantiopurification; Gravity-driven column chromatography; Homo/hetero-chiral intermolecular interaction; SDE (self-disproportionation of enantiomers); SDE-phoric groups.