Synthesis of novel chiral poly(methacrylate)s bearing urethane and cinchona alkaloid moieties in side chain and their chiral recognition abilities

Abstract

Two types of new chiral methacrylates, cinchoninyl(2-methacryloyloxyethyl)carbamate (CIMOC) and cinchonidinyl(2-methacryloyloxy-ethyl)carbamate (CDMOC) were synthesized from 2-methacryloyloxyethyl isocyanate (MOI) and cinchona alkaloid such as cinchonine and cinchonidine, respectively. Radical polymerizations of CIMOC and CDMOC were performed under several conditions to obtain the corresponding polymers whose specific optical rotations ([ α] 435 25) were 84.0–89.0° and 0.39–0.72°, respectively. From the results of radical copolymerizations of RMOC (CIMOC and CDMOC, M 1) with styrene (ST, M 2) or methyl methacrylate (MMA, M 2), monomer reactivity ratios ( r 1, r 2) and Alfrey–Price Q– e were determined: r 1=0.18, r 2=0.48, Q 1=0.53, e 1=0.92 for the CIMOC–ST system; r 1=0.53, r 2=0.26, Q 1=4.91, e 1=1.80 for the CIMOC–MMA system r 1=0.59, r 2=0.47, Q 1=0.86, e 1=0.33 for the CDMOC–ST system; r 1=0.28, r 2=0.59, Q 1=2.15, e 1=1.74 for the CDMOC–MMA system. The chiroptical properties of the copolymers were strongly influenced by co-units. Poly(RMOC)-bonded-silica gel as chiral stationary phase (CSP) was prepared for high performance liquid chromatography (HPLC). The CSPs resolved some racemates such as mandelic acid and trans-2-dibenzyl-4,5-di( o-hydroxyphenyl)-1,3-dioxolane by HPLC. The chiral recognition ability of poly(RMOC) may be due to the interaction between some cinchona alkaloid units and the racemates and/or to secondary and higher-ordered structures of the polymer.