Regioselective Synthesis And Chiral Recognition Of Polysaccharide Derivatives Bearing Different Ester Substituents

Polysaccharide-based chiral stationary phases (CSPs) for high-performance liquidchromatography (HPLC), especially those utilizing phenylcarbamate and benzoate derivativesof cellulose and amylose, are well-known to exhibit high chiral recognition to more than90%of racemic compounds. These derivatives usually have the same groups at the2-,3-and6-positions of a glucose unit. However, only a few studies on the regioselective introductionof different groups at2-,3-and6-position have been carried out until now, which leads to alimitation for extending the polysaccharide derivative family and further investigation on thechiral recognition mechanism as well. Therefore, to develop the efficient CSPs for HPLC withhigh chiral recognition ability, the regioselective synthesis of novel polysaccharide derivativesbearing different groups at2-,3-and6-postions, respectively, was performed in this study,and their chiral recognition ability on the molecular level are further explored.Firstly, a variety of polysaccharide derivatives bearing different ester groups (includingphenylcarbamates and benzoates) were synthesized by the regioselective procedures, and theirstructures were characterized by1H NMR and IR spectroscopy. Then, the CSPs based on theobtained polysaccharide derivatives were prepared by coating on the aminopropyl silica gel,and the chiral columns were prepared by slurry method for HPLC. The coating ratio of CSPswas analyzed by thermogravimetry analysis (TGA). Finally, the chiral recognition abilities ofthe polysaccharide derivatives were evaluated through enantioseparation of nine racematesbased on the novel CSPs by HPLC. The effect of electronic negativity and position ofsubstituents on the chiral recognition ability of derivatives was further investigated.It can be found that polysaccharide derivatives bearing regioselective substituentsexhibited better resolution compared to those bearing monosubstituents, and the formerexhibited higher chiral recognition ability to some racemates than some commercial chiralcolumns. Moreover, the chiral recognition ability of novel polysaccharide derivatives can besignificantly influenced by electronic effect and position of substituents at three positions ofthe glucose unit.