Detection and Amplification of Chirality by Helical Polymers

Abstract

A unique feature of synthetic helical polymers for the detection and amplification of chirality is briefly described in this article. In sharp contrast to host-guest and supramolecular systems that use small synthetic receptor molecules, chirality can be significantly amplified in a helical polymer, such as poly(phenylacetylene)s with functional pendants, which enable the detection of a tiny imbalance in biologically important chiral molecules through a noncovalent bonding interaction with high cooperativity. The rational design of polymeric receptors can be possible by using chromophoric helical polymers combined with functional groups as the pendants, which target particular chiral guest molecules for developing a highly efficient chirality-sensing system. The chirality sensing of other small molecular and supramolecular systems is also briefly described for comparison.

Substituted polyacetylenes

“…89 Recently there are fairly many examples of helical substituted polyacetylenes; for example, induced helices based on the combinations of poly(p-carboxyphenylacetylene) and its analogues with low molecular weight compounds, 29,90 helical poly(p-alkoxy-m,m-dihydroxyphenylacetylene) synthesized by using chiral Rh catalyst systems, 28,91 and poly(menthyl/chiral alkyl propiolates). 92,93 The most salient feature of helical poly(Npropargylamides) developed by us is that the helix is mainly induced by the intramolecular hydrogen bonding between amide groups in the side chain.…”

“…See other reviews as well for photoelectronic functions and liquid crystalline properties of substituted polyacetylenes. 11,19,20,[26][27][28][29] Gas-Permeable Membranes Because of energy saving and environmental issues, the development of separation membranes is now an important subject in industries and our society. 24,103 In fact, various water-purification membranes are now practically utilized on a large scale, and gas separation membranes are also becoming more important.…”

“…In particular, poly[(1-trimethylsilyl)-1-propyne] [poly (11)] is famous because it shows the highest gas permeability among all the existing polymers, and hence its gas permeability has been extensively studied so far. [22][23][24][25] The photoelectronic properties 11,19,20,[26][27][28] and helical structures [27][28][29][30] of substituted polyacetylenes have also been studied considerably.…”

Probing helix propensity of monomers within a helical oligomer

“…M olecular helices are one of the major structural motifs of natural and synthetic polymers and oligomers (1)(2)(3)(4)(5)(6)(7). A fundamental property of a molecular helix is the average length over which it keeps its right-handed (P) or left-handed (M) integrity: the length over which neither uncoiling nor reversal of helix handedness occurs.…”

“…A fundamental property of a molecular helix is the average length over which it keeps its right-handed (P) or left-handed (M) integrity: the length over which neither uncoiling nor reversal of helix handedness occurs. This parameter is important in structural biology because it reflects the stability of, for example, ␣-helical peptides; it is also important in material science because it determines the limit of chiral amplification that a given helical polymeric chain may reach (1,6). Helical integrity may also be useful to remotely control the stereochemistry of a reaction (8).…”