Helical Poly(quinoxaline-2,3-diyl)s Bearing Metal-Binding Sites as Polymer-Based Chiral Ligands for Asymmetric Catalysis

摘要

A helix is one of the simplest and best-organized chiral structural motifs, being widely found not only in molecules, but in natural and artificial materials. Naturally occurring helical macromolecules, such as DNA, RNA, and polypeptides, adopt one of the two helical senses (right or left) and play vital biological roles, which depend on their three-dimensional chiral structure. Helical synthetic polymers have also gained increasing interest on the basis of recent progress in asymmetric polymer synthesis, which has enabled the selective construction of unnatural macromolecular architectures with nonracemic helical structures. Efficient induction of the main chain helical sense to polymers, such as poly(methacrylate)s, poly(isocyanate)s, poly(isocya-nide)s, poly(acetylene)s, and polyguanidines, has been achieved. In the unnatural macromolecular world, even achiral monomers, which have no stereogenic centers, can form helical structures in which either a left- or right-handed helical sense is prevalent.