Synthesis of camphor sulfonic acid derivatives modified Mg/Al-LDH for efficient separation of propranolol enantiomers

Abstract

Designing chiral adsorption separation material with high enantioselectivity and stability is a promising route to realize the enantioselective recognition and separation of racemic molecules. Here, for the first time, camphor sulfonic acid derivatives (CSA) were synthesized as a chiral resolving agent, and it was modified on Mg/Al layered double hydroxide (Mg/Al-LDH) through electrostatic self-assembly to construct functionalized chiral adsorption separation material (CSA@LDH), which could be served as an adsorbent for enantioselective recognition and separation of propranolol enantiomers (R,S-PRO). The CSA@LDH maintained the advantage of limited chiral space in layered structures to achieve the selective enrichment of R-PRO, and the e.e.% value of single separation could reach 19.5%. Meanwhile, density functional theory (DFT) calculations supported that chiral recognition and separation were ascribed to the discrepancy in affinities stemming from the difference of π-π interaction force and hydrogen bonding capacity of CSA with R,S-PRO. Hence, considering the superior ability of hydrogen bond coordination and stereocontrol of camphor sulfonic acid derivatives, it is expected to be more widely used as a chiral resolving agent for other enantiomeric recognition and separation.