Hybridization of helical poly(phenylacetylene)s bearing L-proline tripeptide pendants into porous silica microspheres as a solvent-tolerable chiral stationary phase for liquid chromatography.

A novel one-handed helical copoly(phenylacetylene) (CPA) bearing L-proline tripeptide pendants and a few triethoxysilyl residues was synthesized and hybridized into SiO2 porous microspheres (PMSs) during microsphere growth through the hydrolytic polycondensation of ethoxysilyl groups. Nuclear magnetic resonance and Fourier transform infrared spectroscopy results verified the successful preparation of CPA and its hybrid product using SiO2 PMSs. The chiral recognition ability of the resulting CPA with a hybridized-type chiral stationary phase (HCSP) for high-performance liquid chromatography (HPLC) was investigated, revealing its high recognition ability for selected racemates. Moreover, the HCSP showed good solvent tolerability, thus broadening the selection of suitable eluents. The separation effect of the HCSP for the racemate N,N-diphenylcyclohexane-1,2-dicarboxamide (7) improved significantly after introducing CHCl3 in the eluent, resulting in separation factors equivalent or superior to common commercially available polysaccharide-based chiral stationary phases. The proposed preparation strategy provides a new and valuable method for obtaining poly(phenylacetylene)-based HCSPs suitable for a wide range of applications and eluent conditions.

Synthesis of poly(phenylacetylene)s containing chiral phenylethyl carbamate residues as coated-type CSPs with high solvent tolerability.

Two novel helical poly(phenylacetylene) derivatives containing chiral phenylethyl carbamate residues in the end of each side chain (PPA-S and PPA-R) were synthesized by polymerization of the corresponding phenylacetylene monomers using Rh(nbd)BPh4 as a catalyst in DMF. The enantioseparation properties of the polymers were evaluated as coated-type chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). Under the same chromatographic conditions, PPA-S and PPA-R showed different enantioseparation properties, indicating that the different interactions between the analytes and the polymers, which result from the different chiral phenylethyl carbamate groups in the end of each side chains. Racemates 1, 7, and 8 could be better resolved on PPA-S, while racemate 6 was separated on PPA-R more efficiently. In addition, the coated-type CSPs showed good solvent tolerability and could work without any damage by introducing the polar solvents, such as CHCl3 and THF, in eluent. Moreover, some racemates could be better resolved on these coated-type CSPs with the addition of THF to the eluent.