Helical twist sense bias in oligo(phenylene ethynylene)s induced by an optically active flexible tether

[GRAPHICS] A series of tethered phenylene ethynylene oligomers, which undergo a solvent dependent conformational transition from a random coil to a helix, has been synthesized. The use of trimethylsilyl ether protecting groups on the (+)-tartaric acid-derived tether results in the formation of helices with a large twist sense bias. In contrast, an isopropylidene ketal protecting group or no protecting group is not only ineffective at helical discrimination but may even inhibit helix formation.