Synthesis of a Chiral [2]Rotaxane: Induction of a Helical Structure through Double Threading.

A helically chiral [2]rotaxane featuring two ammonium ion recognition sites in the dumbbell-like component and a calix-bis-crown ether as the macrocyclic component was synthesized, but with no chirality in either individual component. The enantiomeric nature of the isomers, separated through chiral HPLC, was apparent in their CD spectra, which were mirror images for all wavelengths.