| Coating-type chiral stationary phases(CSPs) based on polysaccharide derivatives, cellulose and amylose derivatives in particular, are well known owing to their high chiral resolving capability towards a wide range of chiral compounds. Since cellulose and amylose derivatives can highly swell or dissolve in some organic solvents, the coating-type CSPs based on these polysaccharide derivatives have a lower durability, and can only work in a limited range of eluents. It has been reported that chitin derivatives difficultly dissolved in common organic solvents. Therefore, in order to broaden the application range of CSPs, this work aims at developing novel CSPs with cheap chiral materials. Furthermore, these CSPs will demonstrate good enantioseparation capability and satisfactory tolerability to organic solvents. In order to achieve this goal, on the one hand, two biselector CSPs were prepared by blending chitin and cellulose derivatives; on the other hand, 19 new polymers, including two N-acylated chitosans and 17 novel chitosan bis(arylcarbamate)-(amide) chiral selectors, were designed and prepared from chitosan. New CSPs were obtained by coating these chiral selectors on 3-aminopropyl silica gel. The chiral recognition ability and the durability to organic solvents of as-prepared CSPs were evaluated. The structural dependence of chiral selectors on their performance in chiral separation was discussed. The works implemented in this thesis are summarized as follows:1. Cellulose tris(4-methylbenzoate)(CMB) and cellulose tris(3,5-dimethylphenylcarbamate)(CDMPC) bearing an excellent chiral recognition capability were blended with chitin bis(3,5-dimethylphenylcarbamate)(Chi-DMPC) showing a high solvent tolerance, respectively, at a ratio of 1:1(mol/mol) of glucose unit, and the blends were then coated on 3-aminopropyl silica gel respectively, to afford two biselector CSPs. In comparison with the corresponding single selector CSPs, these biselector CSPs also provided satisfactory chiral recognition capability and the solvent tolerance was improved to a large extent. Besides, the resolution of most analytes was enhanced after the biselector CSPs were analyzed with addictive-containing mobile phases.2. Chitosan I with a viscosity-average molecular weight(M?) of 2.4×105 was prepared by the deacetylation reaction of chitin. Chitosan II with a M? of 1.4×105 was obtained by the degradation reaction of Chitosan I in the presence of hydrogen peroxide. Chitosan II was then modified with an excess of cyclobutanecarboxylic anhydride yielding a completely N-acetylated chitosan(named as II-a). The first series of chiral selectors were prepared by derivatizing II-a with 7 differently substituted phenyl isocyanates. The derivatives were then coated on 3-aminopropyl silica gel to obtain new CSPs. The chiral selectors were insoluble in most organic solvents such as chloroform, ethyl acetate and acetone, however, swelled or dissolved in tetrahydrofuran(THF) at different extent. The swelling or dissolving degree was related to the nature, number and position of the substituent located on phenyl ring. In comparison with CSPs derived from CDMPC and ADMPC, most of above mentioned CSPs possessed an excellent enantioseparation capability. The CSP prepared from chitosan bis(3-chloro-4-methylphenylcarbamate)-(cyclobutylformyamide) showed the strongest enantioseparation capability. This CSP could be analyzed with a mobile phase of 100% ethyl acetate, or 100% chloroform, or 70% THF. The coating-type CSPs derived from CDMPC and ADMPC can not be analyzed with a mobile phase containing ethyl acetate, chloroform, acetone or THF. Compared with cellulose or amylose type of CSPs, this series of CSPs exhibit a better tolerability against organic solvents.3. N-Cyclobutylformylated chitosans I-a and III-a were prepared from chitosan I and III, and the M? of chitosan III was 9.2×105. N-Cyclobutylformylated chitosans I-a and III-a were further modified by 5 phenyl isocyanates with various halogen group(s) on their phenyl ring affording the second series of chiral selectors. These chiral selectors were then coated on 3-aminopropyl silica gel to obtain new CSPs. Same as the first series of chiral selectors, this series of chiral selectors were stable in chloroform, ethyl acetate and acetone, yet swelled or dissolved in THF at different extent. Therefore, to prepare the chiral selectors whose properties in swelling and solubility are similar to those of the chiral selectors in the first series, the N-acylated chitosan with a higher M? must be employed, in which the N-acylated chitosan are modified by using the phenyl isocyanates only with halogen substituent(s). The chiral recognition capability of these CSPs was generally equivalent to or even better than that of the first series of CSPs and the CSPs of CDMPC and ADMPC. The CSP derived from chitosan bis(4-trifluoromethoxyphenylcarbamate)-(cyclobutylformyamide) demonstrated the best chiral recognition capability among the second series of CSPs, and it could also be analyzed with a mobile phase of 100% chloroform, or 100% acetone, or 100% THF. The tolerability of this series of CSPs against organic solvents was remarkably improved.4. Completely deacetylated chitosan(named chitosan IV) with a M? of 2.4×105 was prepared via an intermittent way adopting water-NaOH and n-pentanol-NaOH as the reaction systems. N-Cyclopentylformylated chitosan IV-a was yielded by using cyclopentanecarboxylic anhydride with a larger steric hindrance instead of cyclobutanecarboxylic anhydride as the modifier to derivatived chitosan IV. IV-a was further modified by 5 phenyl isocyanates bearing methyl group(s) on their phenyl ring to afford the third series of chiral selectors. The chiral selectors were then coated on 3-aminopropyl silica gel to obtain new CSPs. The swelling and dissolution characteristics of the selectors were similar to the ones of the first series of chiral selectors, indicated that the chiral selectors prepared from N-cyclopentylformylated chitosan have a higher solubility in THF than those prepared from N-cyclobutylformylated chitosan. Chromatographic separation results exhibited that chiral recognition capability of these CSPs was generally equivalent to or better than that of N-cyclobutylformylated chitosan derivates CSPs and the CSPs of CDMPC and ADMPC. The CSP of chitosan bis(4-methylphenylcarbamate)-(cyclopentylformyamide) exhibited the best chiral recognition capability among the third series of CSPs, and it could also be analyzed with a mobile phase of 100% chloroform, or 100% acetone. The tolerance test in THF is undergoing.In summary, two chitin-cellulose biselector CSPs, and 17 novel chitosan bis(arylcarbamate)-(amide) chiral selectors, and their corresponding CSPs have been prepared. These chitosan derivatives and the CSPs have not been reported. Either the biselector CSPs or the chitosan derivatives CSPs have an excellent enantioseparation capability. Compared with the coating-type CSPs of cellulose and amylose derivatives, the all CSPs prepared in this work exhibited a better tolerability against organic solvents, thus being valuable for practical application. |
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