A short designed semi-aromatic organic nanotube--synthesis, chiroptical characterization, and host properties.

The first generation of an organic nanotube based on the enantiomerically pure bicyclo[3.3.1] nonane framework is presented. The helical tube synthesised is the longest to date having its aromatic systems oriented parallel to the axis of propagation (length similar to 26 angstrom and inner diameter similar to 11 angstrom according to molecular dynamics simulations in chloroform). The synthesis of the tube, a heptamer, is based on a series of Friedlander condensations and the use of pyrido[3,2-d]pyrimidine units as masked 2-amino aldehydes, as a general means to propagate organic tubular structures and the introduction of a methoxy group for modification toward solubility and functionalization are described. The electronic CD spectra of the tube and molecular intermediates are correlated with theoretical spectra calculated with time-dependent density functional theory to characterize the chirality of the tube. Both experimental (NMR-titrations) and theoretical (molecular dynamics simulations) techniques are used to investigate the use of the tube as a receptor for the acetylcholine and guanidinium cations, respectively.