Preparation and evaluation of calix[4]arene-capped beta-cyclodextrin-bonded silica particles as chiral stationary phase for high-performance liquid chromatography

Calix4]arene-capped 3-(2-O-beta-cyclodextrin)-2-hydroxypropoxy]propylsilyl-appended silica particles (C4CD-HPS), a new type of substituted beta-cyclodextrin-bonded chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC), have been synthesized by treatment of bromoacetate-substituted 3-(2-O-beta-cyclodextrin)-2-hydroxypropoxy]propylsilyl-appended silica particles (BACD-HPS) with calix4]arene oxyanions in anhydrous N-methyl-2-pyrrolidone. The synthetic stationary phase is characterized by means of elemental analysis. This new type of CSP has a chiral selector with two recognition sites: calix4]arene and beta-cyclodextrin (beta-CD). The chromatographic behavior of C4CD-HPS was studied with several disubstituted benzenes and some chiral drug compounds under reversed-phase conditions. The results show that C4CD-HPS has excellent selectivity for the separation of aromatic positional isomers and enantiomers of chiral compounds due to the cooperative functioning of calix4]arenes and beta-CDs.