| Enantioseparation is one of the main approaches to obtain theoptical purity substances. Which has important significance in organic chemistry,medicinal chemistry and life science and has become a hot research issue in the world. There are several approaches to obtain enantiomerically pure chemicals. They are crystallization, chemical derivation, biotransformation, extraction, asymmetric conversion and chiral chromatography. The chiral chromatography is more attractive and has been developed rapidly in recent years. However, researcch was concentrated on the chiral stationary phases.The two norvancomycin (NVC) bonded chiral stationary phases used in HPLC were prepared in terms of the different spacer. 1 -, Silica gel was vacuum-dried before use at 150℃.A slurry of silica in dry toluene was heated to reflux,and residual water was azeotropically removed.After that,(3-aminopropyl)triethoxysilane was added and the mixture was heated to reflux for 4h at 110℃.Then, the spacer 1,6-diisocyanatohexane was added to the slurry of (3-aminopropyl)silica gel in dry toluene and the mixture was heated at 70℃ for 2h under a nitrogen atmosphere. The dry norvancomycin was added to the activated silica and the mixture was heated to 70℃ for 12h under nitrogen atmosphere after the residual 1,6-diisocyanatohexane was removed and the Norvancomycin CSP1 was prepared. All reaction were carried out in a homemade apparatus. 2 Norvancomycin was vacuum-dried and then the suspension of norvancomycin in dry pydidine was added a small amount of spacer (3-isocyanatopropyl)triethoxysilane, under a nitrogen atmosphere, and the mixture was heated to 70℃ for lh, with continuous stirring. After cooling to room temperature, a slurry of unmodified silica in dry pydidine was added to the modified selector , and the mixture was heated to 70℃ for 20h, with continuous stirring and then the Norvancomycin CSP2 was prepared.Research on the chromatography performance: 1 Observing the static state adsorption of ibuprofen research on NVC-CSP1. It had different static stateadsorptions of the R and S ibuprofen on NVC-CSP1 which indicated NVC-CSP1 had the capability on enantioseparating ibuprofen.And then the NVC-CSP1 was used to enantioseparate the racemic naproxen under three mobile phases.Naproxen can be chiral separed only under the normal mobile phase. The enantioseparation by hexane/isopropanol=80/20 at the flow rate 1.0 ml/min is good and the naproxen can be base separated, the Rs reached 2.1.2 Enantiomers of 5-Methyl-5-phenylhydantoin were separated on NVC-CSP2.The effects of composition, column temperature, pH, and flow rate of mobile phase on the enantioseparation were investigated. 5-Methyl-5-phenylhydantoin can be chiral separated under reversed phase(methanol/2%TEAA) and polar organic mode(methanol,isopropanol, MeOH/HOAc/TEA) except the nomal phase. The enantioseparation by methanol/2% TEAA (pH5.5) 10/90 at the flow rate 0.6 ml/min and 20℃ is excellent. The racemic dansyl-a-amino-n-butyric acid and naproxen are also chiral separated on the NVC-CSP2 by methanol/2% TEAA (pH7) 1/99 at the flow rate 0.6 ml/min. The resolution of dansyl-a-amino-n-butyric acid and naproxen is 0.37 and 0.9 respectively.The norvancomycin was added in the mobile phase as chiral mobile phase additive on the nonchiral Semmtry C18(150*4.6mm i.d.) to chiral separated naproxen by the methanol/0.25% TEAA (pH5.5) 50/50at the flow rate 0.7ml/min, wavelength 300nm and 25℃ .Which indicated the NVC's enantioseparation capability. The work validated that the NVC-CSP possess good chiral separation capability. The NVC-CSPs are capable of operating in three different mobile phase systems: reversed phase, normal phase, and polar organic mode. Since the NVC-CSPs are covalently bonded to silica gel through chemical reaction, there is no detrimental effect when a column switches from one mobile phase mode to another. So a wide variety of chiral compounds can be chiral separated on the NVC-CSP.
|
PDF Full Text Request