Immobilization of the Ring Inversion Motion in Calix[6]arene by a Cap with C3-Symmetry

Abstract
A conformationally-immobilized calix[6]arene (2) was synthesized for the first time. The immobilization was attained by capping calix[6]aryl 1,3,5-tricarboxylic acid chloride with C3-symmetrical triol. The 1H NMR spectral examination with 2D EXSY established that 2 is immobilized in a cone conformation. Compound 2 showed the high affinity for guanidinium ion because of rigidification of the conformation.