Preparation And Enantioseparation Characteristics Of 6-Amino-6-Deoxyamylose Based Chiral Stationary Phases

In order to resolve and analyze enantiomers of chiral compounds,various chiralstationary phases（CSPs）for high performance liquid chromatography have been developed.Among commercially available CSPs,the ones of coated-type based on cellulose/amylose derivatives possess the strongest chiral separation ability.However,because the chiral selectors on the CSPs can be dissolved or highly swollen in some solvents,the CSPs are seriously restricted in their application range.The chitosan-based CSPs developed by this research group show a low solubility and swelling capacity in most of organic solvents,in order to develop new type of CSPs which cover the advantages of chitosan-and amylose-based CSPs,amino groups were introduced into amylose and then followed by further derivatization,thus improving the tolerance of amylose-based CSPs against organic solvents.In line with this consideration,6-amino-6-deoxyamylose was synthesized with amylose as raw material,and the amino and hydroxyl groups were modified with acid anhydride and isocyanate to afford 7derivatives of amylose-2,3-bis（arylcarbamate）-6-deoxy-6-amide.The corresponding CSPs were prepared with the derivatives as chiral selectors and the enantioseparation ability of these CSPs was evaluated.According to the enantioseparation results,the structure-performance relationship was discussed.Additionally,5 derivatives of amylose-2,3-bis（arylcarbamate）-6-deoxy-6-urea were prepared by reducing the azido group in 6-azido-6-deoxyamylose with triphenylphosphine and the resulted product of the reduction reaction was derivatized with different isocyanates.The works in this thesis are summarized as follows:（1）Crude amylose was purified with a mixture of n-butanol and isoamyl alcohol as the solvent.After being purified,the blue value of the amylose was greater than 0.8.The hydroxyl group at C₆ in the purified amylose was selectively modified by methanesulfonyl chloride and sodium azide in sequence providing 6-azido-6-deoxyamylose.Sodium borohydride was chosen as the reductant to synthesize 6-amino-6-deoxyamylose.The 6-amino-6-deoxyamylose prepared in this way can be dissolved in an acidic aqueous solution.Finally,the amino group in the 6-amino-6-deoxyamylose was modified with benzoic anhydride to yield 6-benzamido-6-deoxyamylose which was characterized by FT-IR,elemental analysis,TGA,¹H NMR,¹H-¹H COSY NMR and ¹H-¹³C NMR.It was found that the hydroxyl group at C6 in amylose molecule was selectively converted to an amino group,and the degree of substitution is above 98%.（2）The amino group of 6-amino-6-deoxyamylose was modified,respectively,with p-methylbenzoic anhydride and 3,5-dimethylbenzoic anhydride,and then the hydroxyl groups were derivatized with aryl isocyanates to provide 7 derivatives of amylose-2,3-bis（arylcarbamate）-6-deoxy-6-（p-methylbenzamido）/（3,5-dimethylbenzamido）.The related CSPs were prepared with the derivatives,and the enantioseparation ability of the CSPs was evaluated by high performance liquid chromatography.It was observed that the nature,position and number of the substituent on the benzene rings at C₂,C₃and C₆,as well as mobile phase composition affected chiral recognition ability of the CSPs.Of the CSPs,the one prepared from amylose-2,3-bis（3,5-dimethylphenylcarbamate）-6-deoxy-6-（p-methylbenzamido）showed the best chiral recognition ability.（3）A new method to convert an azido group to a urea was established:triphenylphosphine was reacted with 6-azido-6-deoxyamylose,and a certain amount of water and excessive isocyanate were then added.By this"one-pot"method,the reduction of the azido group and the subsequent ureidization could be achieved.Meanwhile,the hydroxyl groups in 6-azido-6-deoxyamylose were also carbamylated.The method for the reduction of azido group and subsequent ureidization in this thesis has not been reported.With this method,5 chiral selectors of amylose-2,3-bis（arylcarbamate）-6-deoxy-6-urea were synthesized,the related CSPs were prepared with three of the derivatives,and the enantioseparation ability of the CSPs was evaluated by high performance liquid chromatography.The CSP prepared from amylose-2,3-bis（3,5-dichlorophenylcarbamate）-6-deoxy-6-（3,5-dichlorophenylurea）was observed to show the best chiral recognition ability.The influence of the chiral selector structures on enantioseparation performance was discussed.