Detection and Amplification of a Small Enantiomeric Imbalance in α-Amino Acids by a Helical Poly(phenylacetylene) with Crown Ether Pendants

Abstract

We have designed a novel stereoregular poly(phenylacetylene) bearing the bulky crown ether as the pendant (poly-1) for the amino acid binding site. The polymer forms a one-handed helix upon complexation with l-amino acid perchlorates, and the complexes exhibit an induced circular dichroism (ICD) with the same Cotton effect signs in the polymer backbone region through a significant cooperative interaction. Poly-1 is highly sensitive to the amino acid chirality and can detect an extremely small enantiomeric imbalance in alpha-amino acids (less than 0.005% enantiomeric excess of alanine, for example).