College of Pharmaceutical Science, Zhejiang University of Technology, Chaowang Road 18, Chaohui No. 6 District, Hangzhou 310032, China.
Pharmaceutical Informatics Institute, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310023, China.
J Chromatogr A. 2019 Oct 25;1604:460471. doi: 10.1016/j.chroma.2019.460471. Epub 2019 Aug 22.
The influence of chlorine substituents in chiral separation of three racemic 2-(chlorophenyl)propanoic acids by countercurrent chromatography using hydroxypropyl-β-cyclodextrin as a chiral additive were mainly investigated in the present paper, including 2-(2-chlorophenyl)propanoic acids, 2-(3-chlorophenyl)propanoic acids and 2-(4-chlorophenyl)propanoic acids. The influences of chromatographic conditions on the retention behavior were studied by enantioselective liquid-liquid extraction experiments using the methodology of response surface It was found that 2-(3-chlorophenyl)propanoic acids could be successfully chiral separated by countercurrent chromatography, while no resolution was achieved for racemic 2-(2-chlorophenyl)propanoic acids and 2-(4-chlorophenyl)propanoic acids under optimized separation conditions. The formation of 1:1 stoichiometric inclusion compounds between 2-(3-chlorophenyl)propanoic acids and HP-β-CD was determined by UV spectra measurements. The inclusion constants for 2-(3-chlorophenyl)propanoic acids and HP-β-CD were determined by the Benesi-Hildebrand equation. Meanwhile, the inclusion constants of 2-(3-chlorophenyl)-propanoic acid enantiomer and HP-β-CD were obtained by the pesudophase retention equation in countercurrent chromatography. Furthermore, the inclusion interactions of the three racemates with HP-β-CD were also investigated by the molecular docking. The results obtained from UV spectra measurements and molecular docking showed that the racemate with chlorine substituents in meta-position presented the highest enantiorecognition while the racemates with chlorine substituents in ortho-position had the lowest enantiorecognition. The above results further indicated that forming a stable inclusion complex between racemate and chiral selector is a prerequisite for a successful enantioseparation and at the same time, the difference in inclusion capacity between the two enantiomers is also essential for the enantioseparation.
本文主要研究了手性添加剂羟丙基-β-环糊精对三种外消旋 2-（氯苯基）丙酸对映体通过逆流色谱拆分的影响，包括 2-（2-氯苯基）丙酸、2-（3-氯苯基）丙酸和 2-（4-氯苯基）丙酸。通过响应面法的对映选择性液-液萃取实验研究了色谱条件对保留行为的影响。结果发现，2-（3-氯苯基）丙酸可以通过逆流色谱成功对映体拆分，而在优化的分离条件下，外消旋 2-（2-氯苯基）丙酸和 2-（4-氯苯基）丙酸均未得到拆分。通过紫外光谱测量确定了 2-（3-氯苯基）丙酸与 HP-β-CD 之间形成 1:1 化学计量的包合物。通过 Benesi-Hildebrand 方程确定了 2-（3-氯苯基）丙酸与 HP-β-CD 的包合常数。同时，通过逆流色谱中的拟相保留方程得到了 2-（3-氯苯基）丙酸对映体与 HP-β-CD 的包合常数。此外，还通过分子对接研究了三种外消旋体与 HP-β-CD 的包合相互作用。紫外光谱测量和分子对接的结果表明，对位取代的氯外消旋体具有最低的对映体识别能力，而间位取代的氯外消旋体具有最高的对映体识别能力。这些结果进一步表明，外消旋体与手性选择剂形成稳定的包合物是成功对映体拆分的前提，同时两个对映体之间包合能力的差异也是对映体拆分的必要条件。
