Synthesis And Chiral Recognition Of Amylose Derivatives Bearing Regioselective Ester Substituents

Amylose derivatives are widely used for prepartion chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) due to their excellent chiral recognition abilities. Among these, phenylcarbamate derivatives of amylose exhibit much higher recognition ability. However, the introduction of different substituents onto the three positions of glucose is much less reported. In order to break the limitation of conventional amylose derivatives and develop novel amylose derivatives with high chiral recognition, regioselective synthesis and chiral recognition ability of novel amylose derivatives bearing two different substituents at glucose unit has been performed in this study. The effect of substituents at 2-positions on the chiral recognition ability of amylose derivatives and the releted recognition mechanism was further investigated.The novel amylose derivatives bearing different groups between 2-, 6- and 3-position or 2-,3- and 6-positions of glucose unit were synthesized by the regioselective procedures. The structures and purity of the mediums and final derivatives were characterized by 1H NMR and FT-IR, respective. Then, the coated-type CSPs based on the novel amylose derivatives were prepared by coating method. The coating efficiency was analyzed by thermogravimetry analysis (TGA) and the chiral columns for HPLC were prepared by the slurry method. Finally,the chiral recognition ability of novel amylose derivatives were evaluated by enantioseparation of nine chiral compounds on novel CSPs by HPLC. The effect of structure and electronic effect of the substituents at different positions of a glucose unit on the chiral recognition ability of amylose derivatives were then investigated. By comparing the two series of chiral recognition ability of novel amylose derivatives, their chiral mechanism was further studied.It indicated that novel amylose derivatives bearing different substituents between 2, 3-and 6-positions exhibit good chiral recognition ability such as Troger base,2,3-diphenyloxirane, benzoin, and their separation factor are hign than 1.20. Specially,Amylose-[2,3-di(4-chlorophenylcarbamate)-6-(4-methylbenzoate)] exhibit chiral recognition ability to cobalt triscacetylacetonate, and the separation factor is 1.68. But the novel amylose derivatives bearing different substituents between 2,6- and 3-positions only exhibit chiral recognition ability to Troger base and the separation factor is 1.18. It indicated that novel amylose derivatives bearing phenylcarbamate at 2-positions exhibit good chiral recognition ability than the novel amylose derivatives bearing benzoate at 2-positions.