Preparation And Enantioseparation Characteristics Of Cycloalkylurea Chitosan Derivatives And 2-Amino-Deoxyamylose

Since the earliest discovery that chiral selectors（CS）of polysaccharide derivatives had chiral separation ability,it tookonly several decades to commercialize numerous polysaccharide-typechiral stationary phase（CSP）.In the initial exploration,it was hopted that some CSPs with excllent separation performance could be prepared.After lots ofdevelopments,many polysaccharide-type CSPs with excellent separation performance werefound,suchassomeCSPspreparedfromcellulose tris（3,5-dimethylphenylcarbamate）（CDMPC）andamylosetris（3,5-dimethylphenylcarbamate）（ADMPC）.However,coated-typeCSPsof cellulose/amylosederivatives can only be used in limited mobile phases.If the cellulose/amylose derivatives are bonded on a carrier,the resulted CSP with high tolerability towards organic solvents can be produced,but the enantioseparation ability of the CSPs will be lower than that of the corresponding coated-type CSPs.Later,chitin/chitosan derivatives were also found to have good tolerance in organic solvents,and meanwhile the primary structures of chitin/chitosanare similar to that of cellulose.Therefore,CSPs prepared from chitin/chitosan attracted much more attention.There is a free amino group in chitosan molecule in comparisonwith chitin.Thus,as a chiral source,the hydroxyl and amino groups of chitosan can be selectively modified yielding various derivatives with different structures,which can be employed as CSs.In our research,it was found that ADMPC was better than CDMPC in enantioseparation ability,while the organic solvent tolerance of chitosan CSP is better than that of cellulose CSP.Comparing the primary structure of cellulose,amylose and chitosan,amylose and cellulose are only different in glycosidic linkage,chitosan and cellulose are only different in the substituent at the 2-position.Therefore,if a macromolecule（for example 2-amino-2-deoxyamylose）bears both the glycosidic bond of amylose and the same substituent as chitosan,a CSP prepared with this polymer should be desirable both in high enantioseparation performance and organic solvent tolerance.In view of the above mentioned research background and considerations on the polysaccharide derivative CSPs,in order to develop high-performance polysaccharide derivative chiral separation materials,and clarify structure-performance relationship of enantioseparation materials,in this thesis,the works have been carried out as follows:1.Chitosans with four different molecular weights were used as the raw materials,from which chitosan cyclopentylureas were prepared by converting the amino group at the 2-position into an urea.Then the hydroxyl groups at 3-and 6-positions were derivatizedwith3,5-dimethylphenylisocyanatetoaffordfourchitosan bis（3,5-dimethylphenylcarbamate）-（cyclopentylurea）CSs of different molecular weights.The corresponding CSPs were prepared by coating the derivatives on3-aminopropyl silica gel.The swelling capacity of these CSs in organic solvents and the enantioseparation performance of the four CSPs were tested.The results showed that the CSs of different molecular weights were not significantly different in swellingcapacity.Moreover,the corresponding CSPsexhibited similar enantioseparation performances.In addition,the influence of one enantiomer of a racemate upon the interaction between another enantiomer and a chiral selector was studied by high-performance liquid chromatography with aid of ¹H NMR measurements.2.Six chitosanbis（arylcarbamate）-（cyclohexylmethylurea）s were synthesized and the corresponding CSPs were prepared.Comparingthe enantioseparation abilities of the CSPs derived from chitosan bis（3,5-dimethylphenylcarbamate）-（cyclohexylmethylurea）,chitosanbis（3,5-dimethylphenylcarbamate）-（cyclohexylurea）and chitosanbis（3,5-dimethylphenylcarbamate）-（benzylurea）,the relationship between enantioseparation performance and the structures of the substituents at 2-positionwas studied and discussed.The results show that the substituents at the 2-position of chitosan derivatives significantly affect the enantioseparation performance of the corresponding CSP.Besides,it was also observed that the position,nature,and number of the substituents on the phenyl group all influence the separation performance of the CSPs.3.p-Toluenesulfonylation of amylose was performed.The resulting derivative was characterized by ¹H NMR,¹³C NMR,¹H-¹H COSY NMR and ¹H-¹³C HSQC NMR.It was confirmed that the reaction selectively took place on C-2.The p-toluenesulfonate was then substituted by N₃^-to yield 2-azido-2-deoxyamylosewhich was reducedto provide2-amino-2-deoxyamylose.The reaction conditions of each step were investigated in detail.It was found that the fed ratio of TsCland amylose affected the degree of substitution of tosyl groups.When TsO^-was substituted by N₃^-,temperature was the most important factor.