Synthesis And Enantioseparation As CSPs For HPLC Of Helical Poly(Phenylacetylene)s Bearing L-phenylglycinol Derivatives Pendants

In this work,a series of helical poly(phenylacetylene) derivatives bearing L-phenylalaninol and its derivatives with carbamate group pendants were synthesized,respectively. And their chiroptical properties, as well as enantioseparation abilities as chiral stationary phases (CSPs) for HPLC, were researched.The phenylacetylene monomer with L-phenylalaninol group, N-(4-ethynylbenzoyl)-L-phenylalaninol (PAA-Phg-OH), was synthesized, then eight phenylacetylene monomers with carbamate group were synthesized via the reaction between isocyanate and the active hydroxyl of PAA-Phg-OH,and then polymerized in DMF or THF using a rhodium complex as the catalyst to yield the cis-poly(phenylacetylene)s bearing L-phenylalaninol or its derivatives with carbamate group pendants. The structure of monomers and polymers were characterized by 1H NMR, IR, SEC. The results showed that the main chain of all the polymers possessed cis-transoid configuration.Influence of solvents and temperature on main chain helical conformation of poly(phenylacetylene) derivatives were invesgated vis circular dichroism (CD) spectra and polarimeter. The result indicated that all the poly(phenylacetylene) derivatives presents a biased, one-handed dynamic helical conformation, their main chain helical conformation were various in variable solvents, and the poly(phenylacetylene) derivatives bearing carbamate group pendants may have a tightly twisted helical conformation and lower stereoregularity in THF or CHCl3; the thermodynamic stability of the dynamic helical structures enhanced at lower temperatures, their stereoregularity inceased as the temperature decreased and this phenomenon is reversible within limits; helical conformation of poly(phenylacetylene)derivatives main chain can be changed by anions through the through the host-guest interaction between the amide or hydroxyl groups and anion.The coated-type CSPs were prepared by corresponding polymers using DMF, DMAc or THF as coating solvent and the influence of the introduction of carbamate group, substituent of phenyl carbamate group,and coating solvents on their chiral recognition abilities were invesgated vis HPLC. The result supported that the carbamate group played an important role on chiral recognition of these polymers,and the chiral recognition abilities inceased as the acidity of carbamate amine enhanced, PPAA-Phg-3,5DCPC-1 and PPAA-Phg-3,5DCPC-2 with the with most acidity of carbamate amine among these polymers showed a highest chiral recognition, especially for rac-5, rac-11, rac-12 and rac-15, whose enantiomers were completely separated; the result that CSP-Phg-4CPC/THF and CSP-Phg-3,4DCPC/THF showed high chiral recognition abilities, indicated that tightly twisted helical conformation and suitable array of pendents is good for the formation of chrial cavity with certain steric size,which is responsible for the improvement of enantioseparation ability.