The Separation Of Chiral Drugs By High-speed Counter-current Chromatography

This paper is mainly to research the high-speed countercurrent chromatography(HSCCC) separation of chiral drugs. A total of three racemic intermediates was selected as the research object in the chiral resolution, including phenyl succinic acid(PSA), amlodipine besylate(ADB) as well as equol enantiomers(EQU). Research work and corresponding results obtained from this thesis are mainly as follows:High-speed counter-current chromatography in combination with biphasic chiral recognition technique was successfully applied into the resolution of PSA enantiomers. D-iso-butyl tartrate(D-IBTA) and hydroxypropyl-?-cyclodextrin(HP-?-CD) were employed as lipophilic and hydrophilic selectors dissolved in the organic stationary phase and the aqueous mobile phase respectively. The two-phase solvent system was made up of n-hexane-methyl tert-butyl ether-water(0.5:1.5:2,v/v/v). Impacts of the type and concentration of chiral selectors, the p H value of the aqueous solution as well as the temperature on the separation efficiency were all investigated. By means of the preparative high-speed counter-current chromatography,pure enantiomers were obtained from separating 810 mg of racemate with a purity greater than 99.5%, a recovery rate between 82-85%.Enantiomers of equol were separated by recycling HSCCC using HP-?-CD as chiral selector. The separation was performed with a two-phase solvent system composed of n-hexane-ethyl acetate-0.1 mol/L phosphate buffer solution with p H=7.5(3:7:10, v/v/v) containing the above chiral selectors. The key parameters concerning the two phase system, such as the concentration of chiral selector, the p H value of the aqueous phase solution on the separation efficiency, were all discussed and optimized.Based on the optimized system, a complete HSCCC enantioseparation of 20 mg of equol enantiomers in a recycling elution mode yielded a 8.6-9.0 mg of R-equol and S-equol enantiomers with a purity of 98.5% and a recovery of 86-90%.Biphasic recognition recycling HSCCC was also applied for the separation of ADB enantiomers. The biphasic recognition system was established by adding hydrophilic sulfobutyl ether-?-cyclodextrin(SBE-?-CD) in the aqueous mobile phase and lipophilic D-IBTA in the organic stationary phase, which is capable of preferentially recognizing(+)-enantiomer and(-)-enantiomer respectively. The two-phase solvent system, which was composed of ethyl acetate-aqueous solution(1:1, v/v) plus the above chiral selectors, was selected as per distribution ratios and separation factor of ADB enantiomers. Impacts of the type and concentration of chiral selectors, p H value of the aqueous solution as well as temperature on the separation efficiency were investigated. By means of preparative HSCCC, pure enantiomers were obtained through the separation of 30 mg racemates with a purity greater than97.5% and a recovery rate between 80-84%. Experimental results revealed that biphasic recognition recycling high-speed counter-current chromatography offers a promising means for the highly efficient separation of racemate with a low separation factor.