| As is known to all, a pair of optically pure enantiomers may show great different pharmacological and toxicological activities, and therefore, the separation of enantiomers has been becoming increasingly important. Enantioseparation has been one of the important ways to obtain optical purity compounds, which plays an important role in modern synthetic chemistry, bio-medicine, and agricultural chemicals and so on. Numerous chiral separation methods have been successfully applied to enantiomeric resolution and preparation, such as biological separation, crystallization, chemical separation method, asymmetric conversion, chromatography and so on. Among these methods, the high-performance liquid chromatographic separation of enantiomers using chiral stationary phase (CSPs) is a direct-fast and great potential method, which is important for determining enantiomeric purities and preparing separation for a large scale. The polysaccharide such as cellulose and amylose derivatives are the most widely used in a great deal of CSPs.The esters and carbamates of polysaccharide coated on aminopropyl silica gel have been greatly studied and widely applied for the high-performance liquid chromatography (HPLC) as CSPs. Most of them which exhibit broad applicability to a large number of chiral racemates can be used for a long time with a hexane-isopropanol (90/10, v/v) as the eluent. However, they usually have the shortcomings of poor properties of resisting solvent. The CSPs of immobilized polysaccharide derivatives on aminopropyl silica gel overcome the strict solvent limitation of eluents and have greater flexibility in enantiomeric resolution and preparation.This paper mainly focus on the synthesis and resolution ability of polysaccharide-based coated-type and immobilized-type chiral separation stationary phase which include three parts as the following:Firstly, we prepared the raw materials phenyl isocyanate and aminopropyl silica gel, which structures were characterized by 1H NMR and IR spectrum.Secondly, cellulose and amylose tris(phenylcarbamate) derivatives were synthesized, respectively. 1H nuclear magnetic resonance (1H NMR) and infrared spectroscopy (IR) showed that most of the hydroxyl groups on glucose untis of the cellulose or amylose had been converted into carbamate groups. The chiral stationary phases (CSPs) were prepared by coating CSP-1 or CSP-2 on the aminopropyl silica gel. The chiral recognition abilities of obtained derivatives were evaluated by using 7 typical racemates and a hexane/isopropanol (90/10, v/v) mixture as the eluent. The experimental results show that some racemates were better resolved on the two CSPs. On the whole, CSP-1 and CSP-2 have different chiral resolution ability of some enantiomers. Although CSP-1 has better chiral recognition ability than CSP-2, some racemates which can not be resovled on CSP-1 were better resolved on CSP-2.Finally, the phenycarbamates of cellulose and amylose bearing different amounts of 3-(triethoxysilyl)propyl residues (1%,2%,3%) were synthesized by a one-pot process and efficiently immobilized onto a silica gel through intermolecular polycondensation of the triethoxysilyl groups under acid condition. The structure of the synthesized polysaccharide derivatives was characterized by 1H NMR and IR. The obtained chiral packing materials (CPMs) were evaluated by HPLC. The immobilization efficiencies were calculated by TG. By using the eluents containing chloroform or tetrahydrofuran, which cannot be used with the conventional coated-type CPMs, most of the racemates could be better resolved on immobilized-type CSPs than coated-type CSPs. Many racemates, which can not be resolved on the coated-type CPMs, could be separated on immobilized-type CSPs. |
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