title: Chiral discrimination studies of (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid by high-performance liquid chromatography and NMR spectroscopy.
abstract: Chiral discrimination studies using (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18-C-6-TA) as a chiral selector were performed by high-performance liquid chromatography (HPLC) and NMR spectroscopy. The enantiomers of alanine (Ala) or alanine methyl ester (Ala-ME) were well separated on the chiral stationary phases (CSPs) derived from (+)-18-C-6-TA by HPLC. The chiral selector, (+)-18-C-6-TA, used in the CSP was also applied for the chiral discrimination of the Ala and Ala-ME enantiomers, and it discriminated these enantiomers successfully by NMR spectroscopy. The chemical shift differences (Delta Delta delta) of the alpha-proton of these enantiomers in the presence of an equimolecular solution of 18-C-6-TA were observed to be 0.10 ppm for Ala in methanol-d4 containing 10 mM H2SO4 and 0.11 ppm for Ala-ME in methanol-d4. The observed NMR results agreed with the chromatographic data on the (+)-18-C-6-TA-derived CSP by HPLC in terms of both the elution order and solvents effects.
authors.affiliation: College of Pharmacy, Chosun University, 375 Seoseok-Dong, Dong-Ku, Kwangju 501-759, Republic of Korea. wlee@chosun.ac.kr
authors.forename: Wonjae
authors.initials: W
authors.lastname: Lee
authors.forename: Eunjung
authors.initials: E
authors.lastname: Bang
authors.forename: Chae-Sun
authors.initials: CS
authors.lastname: Baek
authors.forename: Weontae
authors.initials: W
authors.lastname: Lee
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D043844:Crown Ethers / Q000032:analysis* / Q000737:chemistry* / Q000145:classification; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012997:Solvents / Q000737:chemistry*
chemical_list: D043844:Crown Ethers; D012997:Solvents; C090732:18-crown-6 2,3,11,12-tetracarboxylic acid