De novo synthesis of microspheical cellulose 3,5-dichlorophenylcarbamates: An organic-inorganic hybrid chiral stationary phase for enantiospearation

Abstract

High-performance liquid chromatography (HPLC) is one of the most powerful methods to obtain optically pure enantiomers, and chiral stationary phase (CSP) with high mechanical strength and excellent chiral recognition performance is a key for the development of preparative chiral chromatography. Compared to traditional CSPs prepared by coating or immobilizing onto macro-porous silica gel with disadvantages of a limited specific surface area and narrow range of eluents, organic-inorganic hybrids materials on basis of sol-gel chemistry may feature a high density of chiral selectors and excellent mechanical strength. Herein, we reported a de novo synthesis strategy for preparing organic-inorganic hybrid CSPs with good chiral resolution ability and high mechanical strength by sol-gel reactions followed by an end-capping process to eliminate the residual silica hydroxyl groups using cellulose 3,5-dichlorophenylcarbamates and tetraethyl orthosilicate (TEOS) as precursors. The synthesized cellulose-derived CSP was comprehensively characterized by 29Si CP/MAS NMR, FT-IR, TGA, SEM, EDX and BET surface area analysis. Furthermore, seven typical enantiomers were used to evaluate the enantioseparation ability of hybrid CSPs by HPLC, which demonstrated that the hybrid CSPs exhibited similar and even higher chiral recognition abilities to immobilized-type CSP and commercially available Chiralpak IC, such as trans-2,3-diphenyloxirane, 2-phenylcyclohexanone, and benzoin with separation factor (α) of 1.65, 1.44 and 1.10. A series of characterization and results indicated that the organosilica hybrid CSPs prepared in this work have adequate chiral recognition ability for enantioseparation.