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

Abstract

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.

Chiral Stationary Phases for Liquid Chromatography: Recent Developments

“…The most recent crown-ether-based CSPs as well as their chromatographic performance presented on Table S7 (supplementary material). Some of the recent CSPs are based on calix[4]arene derivatives as chiral selectors [233,234,235]. The new derivatives are mainly prepared using click chemistry [234,235].…”

“…Yaghoubnejad et al [234] prepared a calix[4]arene functionalized with two l -alanine units to develop CSP142 (Figure 6), through covalent binding between the allyl groups at the lower rim of the chiral selector and the chromatographic support, using click chemistry. The CSP142 was able to enantioseparate both π-acidic and π-basic analytes.…”

Recent progress to construct calixarene-based polymers using covalent bonds: synthesis and applications

“…Scheme 42 illustrates the structure of alanine-calix [4]arene stationary phase 142 which the allyl groups at the lower rim of calix [4]arene were covalently bonded to silica gel using thiol-ene click chemistry reaction. 114 Finally, Hu et al tried to investigate the retention mechanisms of benzenediol and naphthol positional isomer on a calix [4] arene column using quantum chemistry calculations. 115…”

Highly functionalized calix[4]arenesviamulticomponent reactions: synthesis and recognition properties

“…[8][9][10] The possibility of divers functionalization at lower and/or upper rim as well as unique conformational properties have made calix [4]arenes versatile templates to design outstanding supramolecular structures with several binding sites in an array complementary to a potential guest. [11][12][13] The molecular hosts based on calix [4]arene scaffold have been employed in many applications, 14,15 such as chemical sensing, [16][17][18] drug and gen delivery, [19][20][21][22] enzyme mimicking, 23,24 stationary phase, [25][26][27] extractants, 28,29 enzyme inhibitors, [30][31][32] catalysts [33][34][35] and etc.…”