Synthesis And Chiral Recognition Of Optical Activity Poly(Phenylacetylene) Derivatives As Chiral Stationary Phases

Poly(phenylacetylene) derivatives possessing helical conformation in main chains havegood optical activity and unique properties, and have potential applications in anionrecognition, enantioseparation and luminescence materials. In this work, optically activepoly(phenylacetylene) derivatives bearing L-phenylalanine ethyl ester and L-phenylglycineethyl ester pendants were synthesized, respectively. Then their chiral recognition abilities aschiral stationary phases (CSPs) for HPLC were investigated.Two novel optically active phenylacetylene monomers, N-(4-ethynylphenylcarbonyl)-L-phenylalanine ethyl ester (PA-A-Pha) and N-(4-ethynylphenylcarbonyl)-L-phenylglycineethyl ester (PA-A-Phg), were synthesized via Sonagashira coupling reaction, elimination,eaterification, and amidation reaction. Polymerization of the two monomers was carried outby using Rh(nbd)BPh4as a catalyst in CHCl3or DMF to give optically activehomopoly(phenylacetylene) derivatives HP-PA-A-Pha and HP-PA-A-Phg. The monomersand polymers were characterized by1H NMR, IR, GPC, TG, CD, polarimeter, etc. The resultsindicated that polymerization reaction conditions (reaction solvent, monomer concentration)and external environments (temperature, solvent) have effects on helical conformation ofpolymer main chain. Then corresponding coated-type HP-PA-A-Pha and HP-PA-A-Phg CSPsfor HPLC were prepared, and effects of polymerization reaction conditions, coating solventsand eluent on their chiral recognition abilities were investigated. The separation factor ofrac-2(trans-1,2-diphenyl ethylene oxide) on HP-PA-A-Pha-6using DMF as a reactionsolvent (c=0.10M) reached3.50using hexane/isopropanol(v/v,95/5) as the eluent, which ishigher than the excellent commercial Daicel Chiralpak OD column.A novel monomer, N-(4-ethynylphenylcarbonyl)-aminopropyltriethoxysilane(PA-APTES), was synthesized through amidation reaction and characterized by1H NMR.Copolymerization of PA-A-Pha and PA-APTES was carried out by using Rh(nbd)BPh4as acatalyst in CHCl3or DMF to give a series of copolymers CP-PA-A-Pha, and thecorresponding immobilized-type CSPs were prepared.1H NMR, IR, GPC, TG, CD andpolarimeter were used to characterized the structure and properties of the copolymers, and theinfluences of introduction of PA-APTES, polymerization reaction conditions on molecularweight, immobilization efficiency, optical activity and main chain helical conformation of CP-PA-A-Pha were investigated. Furthermore, the effects of introduction of PA-APTES,polymerization reaction conditions and mobile phase on chiral recognition abilities were alsoinvestigated. The result indicated that the chiral recognition abilities of immobilized-typeCSPs were different from the corresponding coated-typr CSPs. The separation factor ofrac-5(1-(anthracen-9-yl)-2,2,2-trifluoroethanol) on copolymer CP-PA-A-Pha-5using CHCl3as a reaction solvent (c=0.03M) reached2.65using hexane/isopropanol/chloroform (v/v/v,90/1/10) as the eluent, which was higher than the excellent commercial Daicel Chiralpak ODcolumn.