Preparation And Properties Of Chiral Stationary Phases Drived From Acetylated And Urea-based Chitosan Derivatives

High-performance liquid chromatography(HPLC)based on chiral stationary phase(CSP)has been one of the best technology to separate and detect enantiomers.Therefore,it is very important to develop the novel CSPs with powerful enantioseparation abilities and high tolerance to organic solvents for chiral separation and the related fields.In recent yeas,some research groups have reported a number of excellent CSPs based on chitosan derivatives,which have powerful separation capability and high tolerance to organic solvents.However,the relationship between the structure and properties of the chitosan derivatives chiral selectors(CSs)is still unclear.For example,it is not clear whether the properties of CSPs prepared from organism-different chitosans are accordingly different or not;whether the different substituents and functional groups will effect the separation properties of chiral selectors.In order to clarify these problems,the following works have been implemented in this thesis:(1).In order to explore the relationship between the nature of the substituents on the chitosan derivative and the separation properties,chitosan with high deacetylation degree was prepared by using crab shell as raw material.The chitosan was modified by acetic anhydride and aromatic isocyanates in sequence to afford regenerated chitin bis(aromatic phenylcarbamate).The chitosan derivatives were characterized by infrared spectroscopy,nuclear magnetic resonance and elemental analysis.It was coated on 3-aminopropyl silica gel to prepare a chiral stationary phase.Chiral recognition and chiral recognition abilities of these CSPs were tested using 19 chiral compounds.The test results show that the nature of the substituents on the benzene ring affects the chiral recognition performance of CSP,and the CSP of the3-chloro-4-methyl group containing both the electron withdrawing group and the electron donating substituent shows the best chiral recognition abilities.(2).In order to disclose the influence of different sources of chitosan on the performance of the prepared CSPs,chitosan with high deacetylation degree was prepared from shrimp shell,and were afforded three CSPs with the same primary structure as the above-mentioned work with chitin shell.Their chiral recognition abilitiess were tested and compared.It was found that the chiral recognition abilities of CSP prepared from crab shell was better than that of shrimp shell CSP.By comparing the infrared spectrum,it was found that there were some differences in their sprastructure.(3).In order to investigate the relationship between the functional groups and the chiral recognition abilities of chitosan derivatives,in this work,chitosan benzylurea was modified by using chitosan with high deacetylation as raw material.Then chitosan benzylurea was modified by aromatic isocyanates and 3,5-dimethylbenzoyl chloride which has not been reported in the literature.The chitosan derivatives were characterized by infrared spectroscopy,nuclear magnetic resonance spectroscopy and elemental analysis.The chiral recognition abilities of the CSPs were evaluated by using 20 racemates.The results show that in a series of,chitosan-3,6-bis(4-methylphenylcarbamate)shows the best chiral recognition abilities in chitosan-bis(arylphenylcarbamate)-benzylurea derivatives.When comparing the effect of functional groups on chiral recognition abilities,it was found that CSP may perform a better enatiomerseparation capability when its C3 and C6 bearing carbamate at the same time.In summary,11 chitosan derivatives and related CSPs were prepared from chitin in this thesis,and the relationship between suprastructure and chiral recognition abilities of chitosan with different sources was investigated.And the effect of the nature of the functional group on the chiral recognition abilities.Moreover,some of the results observed in this paper may be helpful in developing new enantiomeric materials.