Department of Chemistry, Yunnan Normal University, Kunming 650500, People's Republic of China.
Anal Chem. 2022 Mar 29;94(12):4961-4969. doi: 10.1021/acs.analchem.1c03626. Epub 2022 Mar 21.
Porous organic cages (POCs) are an emerging class of porous materials that have aroused considerable research interest because of their unique characteristics, including good solubility and a well-defined intrinsic cavity. However, there have so far been no reports of chiral POCs as chiral stationary phases (CSPs) for enantioseparation by high-performance liquid chromatography (HPLC). Herein, we report the first immobilization of a chiral POC, NC1-R, on thiol-functionalized silica using a mild thiol-ene click reaction to prepare novel CSPs for HPLC. Two CSPs (CSP-1 and CSP-2) with different spacers have been prepared. CSP-1, with a cationic imidazolium spacer, exhibited excellent enantioselectivity for the resolution of various racemates. Twenty-three and 12 racemic compounds or chiral drugs were well enantioseparated on the CSP-1-packed column under normal-phase and reversed-phase conditions, respectively, including alcohols, diols, esters, ethers, ketones, epoxides, organic acids, and amines. In contrast, chiral resolution using CSP-2 (without a cationic imidazolium spacer)-packed column B was inferior to that of column A, demonstrating the important role of the cationic imidazolium spacer for chiral separation. The chiral separation capability of column A was also compared with that of two most popular commercial chiral columns, Chiralpak AD-H and Chiralcel OD-H, which exhibits good chiral recognition complementarity with the two commercial chiral columns. In addition, five positional isomers dinitrobenzene, nitroaniline, chloroaniline, bromoaniline, and iodoaniline were also well separated on column A. The effects of temperature, mobile phase composition, and injected analyte mass for separation on column A were investigated. Column A also showed good stability and reproducibility after repeated injections. This work demonstrates that chiral POCs are promising chiral materials for HPLC enantioseparation.
多孔有机笼（POC）是一类新兴的多孔材料，由于其独特的性质，包括良好的溶解性和明确的固有空腔，引起了相当大的研究兴趣。然而，迄今为止，还没有关于手性 POC 作为高效液相色谱（HPLC）对映体分离的手性固定相（CSP）的报道。在此，我们首次报道了通过温和的硫醇-烯点击反应将手性 POC NC1-R 固定在巯基功能化硅胶上，以制备新型 HPLC CSP。已经制备了两种具有不同间隔基的 CSP（CSP-1 和 CSP-2）。CSP-1 具有阳离子咪唑间隔基，对各种外消旋体的拆分表现出优异的对映选择性。在正相和反相条件下，CSP-1 填充柱可很好地拆分 23 种和 12 种外消旋化合物或手性药物，包括醇、二醇、酯、醚、酮、环氧化物、有机酸和胺。相比之下，CSP-2（无阳离子咪唑间隔基）填充柱 B 的手性拆分性能不如柱 A，表明阳离子咪唑间隔基在手性分离中的重要作用。还比较了柱 A 的手性分离能力与两种最流行的商业手性柱 Chiralpak AD-H 和 Chiralcel OD-H 的手性分离能力，与这两种商业手性柱表现出良好的手性识别互补性。此外，五种位置异构体二硝基苯、硝基苯胺、氯苯胺、溴苯胺和碘苯胺也在柱 A 上得到了很好的分离。考察了温度、流动相组成和注入分析物质量对柱 A 分离的影响。柱 A 在重复进样后也表现出良好的稳定性和重现性。这项工作表明，手性 POC 是用于 HPLC 对映体分离的有前途的手性材料。
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