Amides of bile acids and biologically important small molecules : properties and applications

Abstract

The research described in this thesis covers the synthesis and characterization of 18 bile acid derivatives of certain biologically important small molecules conjugated via an amide bond. The thread of the research has been the self-assembly studies of the compounds, along with the investigations of the formed systems. A variety of self-assembled systems are shown to be formed by the investigated compounds. Seven of the compounds have been shown to be capable of self-assembly leading to organogelation. The nature of the compound conjugated to the bile acid moiety has proven to be the determinant factor for the gel-forming ability of the compounds. Morphologies of the self-assembled systems have been investigated utilizing microscopic methods. Mainly two kinds of morphologies for the gel samples have been observed - fibrous structures or interconnected sphericals. Moreover, the sample preparation protocol has been shown to affect the sample appearance. NMR spectroscopic methods have been exploited to investigate the interactions involved in the gel formation. Additionally, solid state NMR studies have been performed for the native gel samples. Solid state properties of the compounds have been investigated by means of both powder and single crystal X-ray diffraction along with solid state NMR spectroscopy. Single crystal structures for seven of the compounds have been solved. Moreover, a thermoreversible solid to solid phase transition for one of the compounds has been detected. The preliminary toxicological evaluation for the cysteamine conjugates has been performed. Finally, one of the compounds has been exploited in preparing steroid-capped gold nanoparticles via a single phase reduction process. Basics of supramolecular gels, gold nanoparticles, and bile acids together with the most relevant achievements in the field of bile acid-based nanomaterials are reviewed in the literature part of the thesis.