Preparation And Chiral Separation Of Immobilized Chiral Stationary Phases Based On Amylose Derivatives Bearing Different Ester Groups

High-performance liquid chromatography chiral stationary phase(HPLC-CSP)is one of the most popular and efficient enantioseparation methods.Traditionally,polysaccharide derivatives usually have the same substituents at the 2-,3-and 6-positions of a glucose unit.However,the introduction of different substituents onto the three positions of glucose unit is much less reported.The previous results show that the introduction of different substituents onto different positions has a great influence on the chiral recognition ability of amylose derivatives.Among these derivatives,those bearing para-substituents of phenyl ring of the phenylcarbamates exhibit much higher recognition ability than that of the others.On the other hand,the coated-type CSPs are restricted in the usage of organic solutions,which leads to a limitation in the application of the coated-type CSPs.Therefore,design and development of the immobilized-type CSPs based on the amylose derivatives with regioselective substituents can not only enhance the solvent diversity and stability of the polysaccharide derivatives,but also greatly improve their separation efficiency.Based on the above background,a study on the regioselective synthesis of amylose derivatives and preparation of the immobilized-type CSPs based on them was performed and the chiral recognition ability of the obtained CSPs was investigated in this study.The effect of different polar solvents on the enantioseparation ability of the immobilized-type CSPs was further discussed.Firstly,a novel series of amylose derivatives bearing benzoate at2-position,and para-substituted phenylcarbamates and a small controlled amount of3-(triethoxysilyl)propyl groups at 3-and 6-positions were synthesized by regioselective procedure.The structures and purity of the novel derivatives were then characterized by ~1H NMR and FT-IR.Then,prepare the coated-type and immobilized-type CSPs by coating and immobilization method.The coating efficiency of coated-type CSPs and immobilization efficiency of immobilized-type CSPs were estimated by thermogravimetric analysis(TGA),respectively.Finally,the chiral recognition abilities of amylose derivatives were evaluated through enantioseparation of twelve typical racemates by HPLC.The effects of the nature,structure and immobilization efficiency of different substituents on the chiral recognition ability of the amylose derivatives were investigated.It showed that the immobilized-type CSPs based on the amylose derivatives bearing para-chloro and para-methyl phenylcarbamates at 3-and 6-positions exhibited high chiral recognition ability to many racemates.The resolution of some racemates on these CSPs has been higher than that on the commercialized column.Besides,the increase of the amount of3-(triethoxysilyl)propyl residue has a great effect on the immobilization efficiency and resolution power of this series of immobilized CSPs.