Macromolecular Helicity Induction for Novel Optically Inactive Poly(phenyl isocyanate) Bearing Crown Ether Based on the Host−Guest Complexation

Abstract

The macromolecular helicity induction of a novel optically inactive poly(phenyl isocyanate) bearing crown ether as a host group (2) based on host−guest complexation was discussed. 4‘-Isocyanatobenzo-18-crown-6 (1) was polymerized with MeLi in THF at −78 °C to afford 2 with 71% yield. The circular dichroism (CD) spectrum of 2 in the presence of the perchloric acid salt of l-phenylalanine (l-Phe·HClO4) showed a negative Cotton effect with the high intensity of −3.7 × 104 deg cm2 dmol-1 in the range from 240 to 340 nm, corresponding to the absorption of the polymer backbone, while a positive Cotton effect was observed for d-Phe·HClO4 and the CD spectrum pattern was the mirror image of that of 2 with l-Phe·HClO4. On the other hand, a clear Cotton effect was not observed at all in the range from 230 to 290 nm for the unimer of 2, 4‘-(N,N-diacetylamino)benzo-18-crown-6 (3), with l-Phe·HClO4, though the cation-binding property of 3 was almost the same as that of 2, indicating that the induced CDs were based on n...