Helicity induction on water-soluble oligoresorcinols in alkaline water and their application to chirality sensing

摘要

Oligoresorcinol oligomers were found to adopt a single-stranded helical conformation in alkaline water through intramolecular hydrogen bonds, of which a helix-sense bias was induced by the addition of water-soluble chiral compounds, such as ammonium salts, amines and alcohols.rnWater-soluble artificial helical polymers and oligomers have recently attracted significant attention, since most biomacromolecules with helical structures function in water. Although synthetic chemists have established several approaches for the generation of a number of helical polymers and oligomers in organic media utilizing covalent conforma-tional restrictions, metal complexation, solvophobic effects, hydrogen bonding and charge transfer interactions, only a few water-soluble artificial helical polymers and oligomers have been developed. During the course of our study on developing artificial helical molecules utilizing poly- and oligo(m-phenylene)s that are known to adopt a 5_1-helical conformation in the solid state, but take a random conformation in solution, we have found that oligo(4,6-dihydroxy-m-phenylene)s, i.e., oligoresorcinols self-assembled into double helices in neutral water, which have a high affinity for cyclic and linear oligosaccharides, and form pseudorotaxanes and hetero-stranded double helices, respectively, with a high selectivity to the chain lengths and glycosidic linkage patterns of the oligosaccharides. In this paper, we report water-soluble oligoresorcinols that fold into single helical conformations in alkaline water and their application to chirality sensing for water-soluble optically active compounds.