Development of molecular manipulation technique based on host-guest interactions

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We aimed to develop a molecular manipulation technique on the basis of host-guest interactions. This research constitutes a pioneering work for an intransitive-verb-type technique, which utilizes an ability of organic molecules to assemble through weak chemical bonding automatically. The results are summarized as follows ;1.We employed steroidal molecules, particularly bile acids and their derivatives, as organic hosts. These molecules have been well-known since last century, but their abilities to form inclusion crystals are not known except deoxycholic acid and apocholic acid. We found that most of the steroids form the inclusion compounds with a variety of organic substances. The inclusion behaviors varies from one case to another. This indicates that inclusion phenomena are general in organic substances, because isomers of the steroids amount to over one billion.2.We determined over fifty crystal structures of the inclusion compounds. It was found that facially amphiphilic molecules associate through hydrogen bonding to give bilayred assemblies. Comparative studies of the assemblies clarified that the amphiphilic layrs stack together in various ways. This indicates that asymmetric middle-molecular-weight molecules cause some diversity.3.We confirmed that the controlled combination among multiple hydrogen-bonding groups may serve as the most important step for the manipulation technique of organic molecules. Four or three discrete hydrogen bonding groups associate together in various ways. This diversity is responsible for variable inclusion phenomena which is dependent on the host structures.4.We constructed a system suitable for studying on various aspects of the host-guest interactions by using personal computers. The system enabled us to construct and search a data base of the steroidal inclusion compounds.