Click preparation of a chiral macrocycle-based stationary phase for both normal-phase and reversed-phase high performance liquid chromatography enantioseparation

Chiral polyimine macrocycles (CPMs) constitute a new family of organic macrocycles that have defined cavities, rigid shapes, inherent chirality and multiple cooperative binding sites, and have shown great po-tential in diverse areas. However, the application of CPMs for high performance liquid chromatography (HPLC) enantioseparation has rarely been reported. In this work, a novel chiral stationary phase (CSP) for HPLC was prepared by chemical bonding of a CPM (C54H72N6O3) onto thiolated silica via thiol-ene click reaction. The CSP exhibited good enantioselectivity in both normal-and reversed-phase HPLC. Chi-ral compounds included alcohols, diols, ketones, organic acids, esters, ethers, amines, and epoxides were enantioseparated on the column in normal-phase mode (17 compounds) and reversed-phase mode (20 compounds). Importantly, broader chiral resolution was observed with the column than that obtained us-ing our previously studied chiral macrocycle H3L-based column, indicating the potential to significantly improve and broaden applicability of this novel macrocycle-type CSPs. Moreover, the CSP exhibited good complementary enantioseparation to Chiralpak AD-H and Chiralcel OD-H columns, enabling separation of some racemates that could not be separated by the two popular chiral HPLC columns. In addition, the fabricated column exhibited good stability and reproducibility. The relative standard deviations (RSDs) ( n = 5) of retention time and resolution after multiple injections were < 0.20 % and < 0.39 %, respec-tively. The results demonstrated the great potential of this type of CPM for HPLC separation of enan-tiomers.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

Chiral polyimine macrocycles are a new family of organic macrocycles that have defined cavities, rigid shapes, inherent chirality, and multiple cooperative binding sites, and show great potential in diverse areas. However, their application in high-performance liquid chromatography (HPLC) for enantioseparation is rarely reported. In this study, a novel chiral stationary phase (CSP) for HPLC was prepared by chemically bonding a chiral polyimine macrocycle onto thiolated silica. The CSP exhibited good enantioselectivity in both normal- and reversed-phase HPLC, and showed broader chiral resolution compared to a previously studied chiral macrocycle-based column. It also showed complementary enantioseparation to other popular chiral HPLC columns and demonstrated good stability and reproducibility.