posted on 2007-04-17, 00:00authored byKevin K. L. Cheuk, Jacky W. Y. Lam, Bing Shi Li, Yong Xie, Ben Zhong Tang
Phenylacetylene derivatives containing different sugar moieties and functional bridges (1−5)
are synthesized. Their polymerizations are affected by organorhodium complexes, producing corresponding
polymers P1−P5 with high molecular weights (Mw up to 1.2 × 106) and stereoregularities (Z content up to
100%) in high yields (up to 99%). The polyene backbones undergo irreversible Z-to-E isomerization at ∼160−230 °C. The solutions of the polymers exhibit solvatochromism: their backbone absorptions change with variations
in the surrounding media. The polymers show Cotton effects in the long wavelength region where their polyene
backbones absorb, revealing that the chiral sugar pendants have induced the polymer chain to take a helical
conformation with an excess in one-handedness. Inserting a flexible methylene spacer between the chiral pendant
and the polyene backbone hampers the helicity induction process and lowers the backbone circular dichroism.
The acetonide protection groups in most of the polymers can be selectively deprotected by acid-catalyzed hydrolysis,
yielding polymers with “free” sugar appendages. The polymers are cytophilic and can stimulate the growth of
living cells.