Preparation and evaluation of a chiral HPLC stationary phase based on cone calix[4]arene functionalized at the upper rim with l-alanine units.

Here we report a new chiral stationary phase (CSP) immobilized on silica gel based on cone calix[4]arene functionalized at the upper rim with two l-alanine units as new chiral selector that has been used in high-performance liquid chromatography. The CSP was prepared by covalently bonding the allyl groups at the lower rim of calix[4]arene to silica gel by thiol-ene click chemistry reaction. Elemental analysis of the CSP showed that 120 μmol of chiral selector bonded per gram of silica gel. 1-Hexene was used for end-capping of unreacted mercapto groups on silica gel. Since the CSP is chemically bonded to the silica, it can be used in the normal-phase and reversed-phase mode and with halogenated solvents as mobile phases, if desired. The chromatographic performance of the CSP was evaluated in the enantioseparation of the 3,5-dinitrobenzoyl derivatives of some amino acids, diclofop-methyl and dl-mandelic acid.
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