Molecular cleft possessing a cholic acid moiety as a podant and its conformation

Abstract

A cleft type host molecule 4 possessing a cholic acid moiety as a podant was synthesized from the condensation of naphthalene-1,4,5,8-tetracarboxylic dianhydride with a 3α-aminocholanoate derivative. It was found that 4 could be associated with naphthalene-2,6-dimethanol 5 with the binding constant of 71–92 M^–1 with a host–guest ratio of 1∶1 from ¹H NMR spectrometric titration. Conformational analysis of 4 in the absence or the presence of 5 was carried out by variable temperature ¹H NMR spectroscopy. Without a guest molecule, 4 adopted two stable conformations at 213 K, however, a single different conformation was found in the presence of 5. The cleft type conformation of 4 was induced by the inclusion of the guest molecule.