Chromatographic enantioseparation by poly(biphenylylacetylene) derivatives with memory of both axial chirality and macromolecular helicity

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Abstract
Novel poly(biphenylylacetylene) derivatives bearing two acetyloxy groups at the 2‐ and 2′‐positions and an alkoxycarbonyl group at the 4′‐position of the biphenyl pendants (poly‐Ac's) were synthesized by the polymerization of the corresponding biphenylylacetylenes using a rhodium catalyst. The obtained stereoregular (cis‐transoidal) poly‐Ac's folded into a predominantly one‐handed helical conformation accompanied by a preferred‐handed axially twisted conformation of the biphenyl pendants through noncovalent interactions with a chiral alcohol and both the induced main‐chain helicity and the pendant axial chirality were maintained, that is, memorized, after complete removal of the chiral alcohol. The stability of the helicity memory of the poly‐Ac's in a solution was lower than that of the analogous poly(biphenylylacetylene)s bearing two methoxymethoxy groups at the 2‐ and 2′‐positions of the biphenyl pendants (poly‐MOM's). In the solid state, however, the helicity memory of the poly‐Ac's was much more stable and showed a better chiral recognition ability toward several racemates than that of the previously reported poly‐MOM when used as a chiral stationary phase for high‐performance liquid chromatography. In particular, the poly‐Ac‐based CSP with a helicity memory efficiently separated racemic benzoin derivatives into enantiomers.
Funding Information
  • KAKENHI from the Japan Society for the Promotion of Science (JSPS) (16H04154 (K.M.) and 25220804 (E.Y.))

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