POLYMERIC CHIRAL CROWN ETHERS .8. SYNTHESIS OF OPTICALLY-ACTIVE POLY(DIBENZO-19-CROWN-6)S VIA CYCLOPOLYMERIZATION OF DIEPOXIDES

Chiral diepoxides, (2R,18R)-(-)- and (2S,18S)-(+)-5,6:14,15-dibenzo-1,2:18,19-diepoxy-4,7,-10,13,16-pentaoxanonadeca-5,14-diene [(R,R)-(-)-1 and (S,S)-(+)-1], were synthesized enantiomerically and polymerized with a Lewis acid and KOH. All the polymers obtained were soluble in CHCl3 and consisted essentially of cyclic repeating units. The CD spectra of polymers from (R,R)-(-)-1 showed a positive Cotton effect, while the polymers from (S,S)-(+)-1 presented a mirror image CD curve with a negative Cotton effect. The polymers obtained with KOH possessed higher stereoregularity than those with a Lewis acid. The stereochemistries of polymers from (R,R)-(-)- and (S,S)-(+)-1 with KOH were poly[(R,R)-dibenzo-19-crown-6] and poly[(S,S)-dibenzo-19-crown-6], respectively. Polymers 2 and 8 obtained from (S,S)-(+)-1 with SnCl4 and KOH, respectively, formed the host-guest complex dominantly with the D-isomers of phenylglycine, phenylalanine, and methionine methyl esters. The optical purities of guests extracted by the both polymers were as low as values ranging from 0.5 to 5.4%. For every host-guest system, the chiral recognition property of polymer 8 was higher than that of polymer 2.