[External stimulus-responsive conformational alterations of aromatic amides].

Three-dimensional structure of a molecule and its alteration is an important issue, and it is essential problem for controlling the function of a molecule such as a molecular switch or device. In most cases, molecular switches have relatively high activation energy for interconversion between alternative structures, however in some biological systems, conformational preference plays an important role in regulation of bioactivity. We have interested in conformational alteration of aromatic amides, which have interesting features about conformation. Most of secondary aromatic amides such as benzanilide tend to prefer trans conformation, whereas N-methylation makes its conformation cis-favored. Recently we found several aromatic amides altered the preferred conformation depending on the external stimuli. Thus, N-phenyl-N-quinonyl type of amides changed their preferred conformation according to redox state of quinonyl moiety. N-Methyl pyridylamides showed conformational alteration according to solvent acceptor ability or addition of acid. N-Methylated pyridylamide oligomer also showed unique conformational folding and unfolding. These properties of the aromatic amides can be applied to stimuli-responsive molecular switches and functional molecules.