Regioselective Synthesis And Chiral Recognition Ability Of Novel Amylose Derivatives

By far,polysaccharide derivatives are the most popular manufacturing materials to prepare chiral stationary phases(CSPs)for high-performance liquid chromatography(HPLC)due to their excellent chiral recognition ability.Among these,phenylcarbamate derivatives of cellulose and amylose exhibit much higher recognition ability than that of the others.Traditionally,amylose derivatives usually have the same structural substituents at the 2-,3-and 6-positions of a glucose unit.However,the introduction of different substituents onto the three positions is not so much reported comparatively,which lead to a limitation of the development of amylose derivatives and investigation into their chiral recognition mechanism to a large extent.Based on the above status,a study on the regioselective synthesis and chiral recognition ability of novel amylose derivatives bearing two different substituents at all three positions of a glucose unit has been performed in this study.The effect of substituents at different positions on the chiral recognition ability of amylose derivatives and then the recognition mechanism was further investigated.Firstly,novel amylose derivatives bearing two different phenylcarbamates with different side groups between 2-,6-and 3-positions were synthesized by regioselective procedures.The reaction process was monitored by FT-IR,and the structures and purity of the novel derivatives were then characterized by ~1H NMR and FT-IR,and the substitution degrees at different positions of the glucose unit were confirmed.Secondly,the coated-type CSPs for HPLC were prepared by coating method based on the novel amylose derivatives synthesized in the first step.The coating efficiency was analyzed by thermogravimetry analysis(TGA)and the chiral columns were then prepared by the slurry method.Thirdly,to evaluate the chiral recognition ability of novel amylose derivatives,twelve chiral compounds with typical structures were resolved using the prepared 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.The influence of the polarity of eluents on the chiral recognition ability of novel amylose derivatives by changing the ratio of eluent components was further studied.It shows that novel amylose derivatives bearing different substituents between 2-,6-and3-positions exhibit good chiral recognition ability to many racemates,some of which can be separated with a higher resolution efficiency than that on the commercial columns.Besides,the property and structure of substituents at all three positions can significantly influence the chiral recognition ability of amylose derivatives.Particularly,the introduction of electron-donating groups at 2-and 6-positions will effectively improve the chiral recognition ability of amylose phenylcarbamates,when the substituents at 3-position is constant.