Synthesis of Optically Active Polymethacrylates Bearing Axially Dissymmetric 1,1′-Binaphthalene Skeleton as a Pendant Group and Their Optical Resolution Ability as Chiral Adsorbent for HPLC

Abstract

Abstract Optically active polymethacrylates 6 and 8, which have pendant axially dissymmetric 1,1′-binaphthalene moiety, were synthesized by radical polymerization of (S)-2-methacryloyloxy- and (S)-2-(3-methacryloyloxypropoxy)-2′-methoxy-1,1′-binaphthalene, respectively. Specific rotation and CD spectrum of 6 are rather different from those of the model compound 2-(2,2-dimethylpropanoyloxy)-2′-methoxy-1,1′-binaphthalene (7), while the chiroptical properties of 8 are almost the same as those of the corresponding model compound. The difference of the chiroptical properties between 6 and 7 was attributed to the difference of the dihedral angles between the naphthalene planes of the 1,1′-binaphthalene skeleton. The polymethacrylates 6 and 8 were coated on a spherical silica gel to give HPLC chiral stationary phases (CSP-6 and CSP-8). These CSPs differentiated several enantiomeric 1-aryl-1-alkanols and 1,2-diols as the 3,5-dinitrophenylcarbamates, CSP-8 showing better resolution than CSP-6. Furthermore, (S)-2-(5-carboxypentyloxy)-2′-methoxy-1,1′-binaphthalene, a model compound of 8, was prepared and covalently bonded to an aminopropylsilanized silica gel to afford CSP-16, which also resolved these racemates. Thus, the chiral discriminating ability of the polymethacrylate 8 would be based not on the secondary and/or higher-ordered structure, but mainly on the interaction between the individual 1,1′-binaphthalene units of 8 and the racemates.