title: Enantioseparation of aromatic α-hydroxycarboxylic acids: the application of a dinuclear Cu₂(II)-β-cyclodextrin complex as a chiral selector in high speed counter-current chromatography compared with native β-cyclodextrin.
abstract: The use of a dinuclear Cu2(II)-β-cyclodextrin complex (Cu2-β-CyD) as a chiral selector (CS) was successfully applied to chiral high speed counter-current chromatography (HSCCC) for the enantioseparation of aromatic α-hydroxycarboxylic acids. α-cyclohexylmandelic acid (CHMA) as a case was studied to optimize the separation temperature, the pH value of the aqueous phase, and the concentration of the chiral selector, which were comparatively studied between Cu2-β-CyD and native β-cyclodextrin (β-CyD) as CSs. The thermodynamic parameters of the formation of the complex between the enantiomers and the CSs were obtained, and the complex formation constants between the enantiomers and Cu2-β-CyD or β-CyD were determined using induced circular dichroism technology. The results indicate that Cu2-β-CyD can remarkably improve the enantioseparation compared with β-CyD, mainly due to the ion-pairing interactions between the deprotonation of carboxyl group of CHMA and the Cu(II) ion of Cu2-β-CyD. Five of other aromatic α-hydroxycarboxylic acids were also enantioseparated successfully by HSCCC using Cu2-β-CyD as a CS.
authors.affiliation: State Key Laboratory of Natural Medicines, Department of Natural Medicinal Chemistry, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing 210009, Jiangsu, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Han
authors.affiliation: State Key Laboratory of Natural Medicines, Department of Natural Medicinal Chemistry, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing 210009, Jiangsu, China.
authors.forename: Jianguang
authors.initials: J
authors.lastname: Luo
authors.affiliation: State Key Laboratory of Natural Medicines, Department of Natural Medicinal Chemistry, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing 210009, Jiangsu, China.
authors.forename: Jinfang
authors.initials: J
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Natural Medicines, Department of Natural Medicinal Chemistry, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing 210009, Jiangsu, China.
authors.forename: Yingqi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Natural Medicines, Department of Natural Medicinal Chemistry, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing 210009, Jiangsu, China.
authors.forename: Yucheng
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Natural Medicines, Department of Natural Medicinal Chemistry, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing 210009, Jiangsu, China.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Natural Medicines, Department of Natural Medicinal Chemistry, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing 210009, Jiangsu, China. Electronic address: cpu_lykong@126.com.
authors.forename: Lingyi
authors.initials: L
authors.lastname: Kong
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry / Q000302:isolation & purification*; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D056831:Coordination Complexes / Q000378:metabolism*; D003377:Countercurrent Distribution / Q000379:methods*; D012997:Solvents; D013237:Stereoisomerism; D013816:Thermodynamics; D047392:beta-Cyclodextrins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D002264:Carboxylic Acids; D056831:Coordination Complexes; D012997:Solvents; D047392:beta-Cyclodextrins; C031215:betadex
keywords: Aromatic α-carboxylic acid; Chiral separation; Cu(2)(II)-β-cyclodextrin; High speed counter-current chromatography; α-Cyclohexylmandelic acid