Synthesis And Properties Of Bile Acid Conjugates

Bile acids are a class of naturally occurring amphiphilic compounds. Because of their facial amphipathy, rigid hydrophobic backbone, active reactivity, biocompatibility and low price, they have attracted great attentions in supramolecular chemistry. In order to make full use of the unique molecular structure of bile acids, we design and synthesize a series of novel bile acid conjugates with known function systems, and study their supramolecular assembly, supramolecular recognition, and surface modification properties. The major work is as follows:A series of novel bile acid-glutamic acid conjugates have been synthesized and their supramolecular assembly behaviors have been systematically investigated. The free carboxylic end provide the flexibility to induce the supramolecular assembly by coordinate interaction with Cu2+ and hydrogen bond interaction with 4, 4-bipyridine(4py). The lithocholic acid-glutamic acid conjugate maintained a suitable hydrophiliclipophilic balance and have showed better molecular induced assemble behaviour and versatile gelation ability. The detailed investigations by SEM, XRD, FTIR, and molecular simulation have been analyzed to probe the self-assembly mechanism.A series of bile acid-tetraphenylethylene conjugates have been designed and synthesized. It is found that the synergetic combination of the distinct properties of both TPE and two cholic acid units could directly afford uniform fluorescent vesicles with amphiphilic binding pockets in membrane. This structural feature of such vesicles provides a unique opportunity for facile construction of functional chemical systems through host-guest chemistry,as exemplified by the creation of FRET systems. Thus, we believe that this new type of fluorescent vesicles could hold great potential for the development of functional nanosystems and nanomaterials.We newly designed and synthesized a novel tetraphenylethylene-cholic acid tweezer with aggregation-induced emission property. In nonpolar solvents, the conjugate could bind hydrophilic saccharide molecules through hydrophilic cavity and turn on the fluorescence. Binding is evidenced by changes in the fluorescence spectra with size selectivity, and the receptor exhibits higher selectivity for oligosaccharides over monosaccharide.We newly designed and synthesized a novel cholic acid-dopamine conjugate(CA-DOPA). The monolayer cholic acid functionalized gold nanoparticle was prepared through one simple step. In this strategy, the cholic acid-dopamine conjugate served multiple roles: as a reducing agent, an anchoring chemistry and a protective agent. Due to the facial amphipathy of cholic acid, Au@CA-DOPA could disperse in the polar/ apolar solvent, and bind hydrophobic fluorescence molecules through hydrophobic cavity in polar solvent, realizing surface energy transfer(SET) phenomenon. We also study the supramolecular assembly and optical properties of poly CA-DOPA spheres, it helps us to have a deep insight in the mechanism of dopamine polymerization, and meanwhile these spheres have potiential applications in biological detection and imaging.