Supramolecular Chemistry Of Bile Acid Derivatives

Bile acid is a class of natural occurring compounds, with a rigid hydrophobic backbone, a curved profile and facially amphiphilic characteristic. Due to its unique structure, bile acid has been presented as one of the most important platforms for the construction of functional supramolecular system. In this dissertation, we focused on the design and synthesis of a series of novel dimeric bile acid derivatives and bile acid derived conjugated polymers. Their structures were identified by means of spectroscopic methods, the preliminary bioactivity was screened and their conformation in solvents as well as their self-assembly properties were studied. The major work is as follow:Nine dimeric bile acid conjugates linked by amino acid moieties have been synthesized in a facile way and their unique amphiphilic conformation was confirmed by dye extraction experiment. The compounds show modest antiproliferative activity against MCF-7 cancer. Dimeric cholic acid linked by a hydrophobic linker exhibits the more significant cytotoxic activity.A series of dimeric bile acids linked by 4, 4'-diaminoazobenzene were synthesized. The process of trans-cis photoisomerization, which was sensitive to the molecular structure and solvent used, was considerably slow due to the large and rigid skeleton of bile acid. Depending on the trans-cis photoisomerization of azobenzene moiety, the structure-activity relationship of these dimeric bile acid derivatives was preliminarily established. When these bile acid dimers adopt a cis configuration, a more significant antibacterial activity against E. coli DH5αcan be observed.The self-assembly behavior of bile acid dimers linked by conjugated moieties, including azobenzene and oligo(p-phenyleneethynylene), were studied. In the case of oligo(p-phenyleneethylene) bearing dimeric deoxycholic acid end groups, the addition of water to THF can lead to a highly interesting twist assemblies, which is the result from the combination of hydrogen bonding,π-πstacking and hydrophobic interaction. Varying the kinds of bile acid led to nanostructures with drastically different morphologies.A series of novel bile acid decorated poly(p-phenyleneethynylene) have been synthesized. The facially amphiphilic property of bile acid can increase the biocompatibility and endow remarkable solvatochromism to the conjugated system. Moreover, the cholate group can mediate the organization of PPE backbone and afford nano-scale assemblies with adjustable size and morphology.We have attempted to obtain bile acid functionalized conjugated polymers by electropolymerization."Click"chemistry, specifically Huisgen 1, 3-dipolar cycloadditions, was used as a general methodology for the functionalization of the formed polypyrrole films on electrodes. Several bioactive compounds, including bile acid, nucleic acid and protein can be bound onto the electrode surfaces without the loss of their functionality and the electroactivity of the underlying conducting polymers.