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

A cleft type host molecule 4 possessing a cholic acid moiety as a pedant wa s synthesized from the condensation of naphthalene-1,4,5,8-tetracarboxylic dianhydride with a 3 alpha-aminocholanoate derivative. It was found that 4 could be associated with naphthalene-2,6-dimethanol 5 with the binding cons tant of 71-92 M-1 with a host-guest ratio of 1 : 1 from H-1 NMR spectrometr ic titration. Conformational analysis of 4 in the absence or the presence o f 5 was carried out by variable temperature H-1 NMR spectroscopy. Without a guest molecule, 4 adopted two stable conformations at 213 K, however, a si ngle different conformation was found in the presence of 5. The cleft type conformation of 4 was induced by the inclusion of the guest molecule.