Preparation And Enantioseparation Characteristics Of Chiral Separation Materials Drived From Polysaccharide Carbamate Derivatives

Coated-type chiral stationary phases(CSPs)based on polysaccharide carbamate derivatives,the ones of cellulose and amylose in particle,are well known for their powerful chiral separation performance,thus being applied widely for the enantioseparation of chiral compounds.However,the applications of these CSPs are limited because the derivatives of cellulose and amylose can highly swell or even dissolve in some organic solvents,such as tetrahydrofuran(THF)and chloroform etc.It has been reported that the derivatives of chitin and chitosan difficultly dissolved in common organic solvents.Therefore,in order to broaden the practical range of CSPs,cheap and easily available polysaccharides,such as chitin etc.,were applied as chiral materials to prepare the CSPs with high separation performance and powerful eluents tolerance.The relationship between structure and performance was discussed.The works in this thesis are summarized as follows:1.Nature and regenerated chitins with different molecular weight were derivatized with 3,5-dimethyphenyl isocyanate.The corresponding chiral stationary phases(CSPs)were prepared by coating the resulting chitin derivatives on 3-aminopropyl silica gel.The swelling capacity of the chitin derivatives,enantioseparation capability as well as eluents tolerance of the CSPs were evaluated.The results demonstrated there was no remarkable difference in enantioseparation capability between natural and regenerated chitins based CSPs.The similar enantioseparation characteristics of two CSPs could be understood by comparing the IR spectra of related chitin derivatives.With regard to the two CSPs that exhibit similar enantioseparations,when compared the IR spectra of their chiral selectors,the shapes of absorption peak resulted from typical functional groups are found to be similar.This observation insinuates the suprastructures of the two relevant chiral selectors are similar.The one of the two CSPs prepared by coating the chitin derivative with a lower molecular weight generally provided better enantioseparations.All CSPs can work in 100%chloroform,100%ethyl acetate,100%acetone and the mobile phases containing a certain amount of tetrahydrofuran(THF).The CSP prepared from the chitin derivative with the higher swelling capacity exhibited better enantioseparations than others.2.Chitosan with different viscosity-average molecular weights(Mv:3.1×10~5 and2.4×10~5)were used for the raw material to prepared chitosan-(4-methylbenzyl urea)s which were then modified by eight phenyl isocyanates with different substituents.The corresponding CSPs were prepared with these derivatives as chiral selectors.All CSPs showedbetterenantioseparation capability and could be analyzed with the mobile phases of100%chloroform,100%ethyl acetate,100%acetone and the one containing a certain amount of tetrahydrofuran(THF).The CSP derived from chitosan derivatives with electron-donating substituent(e.g.methyl group)at para-position of benzene ring showed better chiral recognition ability than those with electron-withdrawing substituent at the same position.The CSPs prepared from the chitosan derivatives with chloro substituent at para-position of benzene ring exhibited distinct enantioseparation performance in comparison with the CSPs bearing the same substituent,the position and number of which were different.The chiral recognition ability with obvious difference between 4-chloro substituents on benzene of CSP and the other CSP based on chloro substituented phenylcarbamate derivatives of chitosan.Based on the IR spectra of the chiral selectors,from suprastructure point of view,the difference in separation performance of these CSPs was discussed and explained.3.Cellulose tris(3,5-dimethylphenylcarbamate)(CDMPC)were prepared by two different ways.The first method was that the cellulose was swollen in pyridine in advance,and then was derivatized.The second method was that the cellulose and isocyanate were simultaneously mixed in pyridine,in which the cellulose was derivatized without swelling in advance.It was found that the CDMPC prepared by first method showed better chiral recognition ability.Besides,the enantioseparation capability of the crude CDMPC was dried by heating for a long time was not significantly different from that of the crude CDMPC was not dried in prior to purification.In summary,in this thesis,16 polysaccharide derivatives and related CSPs were prepared from chitin,chitosan and cellulose.The enantioseparation capability,eluents tolerance as well as the relationship between structure and performance of the CSPs based on chitin and chitosan derivatives were discussed.The works in this thesis have not been reported.The CSPs prepared from the derivatives of chitin and chitosan all possessed better enantioseparation performance.Practical range of mobile phases was greatly broadened by the CSPs prepared in this thesis.Moreover,the relationship between structure and performance of polysaccharide derivative CSPs was further understood,which might be valuable reference for the investigation of chiral separation materials.