Smart rotaxanes: Shape memory and control in tertiary amide peptido[2]rotaxanes

The structures of the first tertiary amide peptide rotaxanes are established in solution by H-1 NMR spectroscopy and in the solid state by ii-ray crystallography. The hydrogen bonding networks which template the rotaxane formation "live on" in nonpolar solvents and strongly influence either the tertiary amide rotamer distribution or the rate of interconversion between the rotamers depending upon the peptide sequence. The intercomponent interactions-and their influences-can in appropriate cases be "switched off" by polar solvents leading to "smart" molecular systems which are flexible or adopt several shapes in one environment but transformed to rigid or single-shaped species in another.