Synthesis And Properties Of Gelators Based On Triterpenoid

Glycyrrhetinic acid (GA) and oleanolic acid (OA) are two typical pentacyclictriterpenoids and both possess special characteristics such as chiral rigid skeletons,relative low toxicity, and biocompatibility. They have been well known for theirbiological activities such as antitumour, anti-virus and anti-fungal. In this dissertation,due to the aggregation trend of their skeleton, we design and synthesize a series oftriterpenoid conjugates as new gelators by introduction of some functional groups whichcan provide non-covalent interactions. Imitating and modifying these natural productsused as building blocks in self-assembling architectures can not only minimize thetedious synthetic work, but also make use of natural products to create new materials.The major contents are as follows:A tweezer based on uracil-appended glycyrrhetinic acid linked by1,2,3-triazolewith excellent gelation ability was synthesized. Intermolecular hydrogen bonds and π-πinteraction were confirmed to be the driving forces for the gel formation. The gel-to-solphase transition process could be selectively controlled by interaction with both cationsand anions such as F-and Hg2+separately. In addition, an oleanolic acid-adenineconjugate was designed and synthesized, and it can self-assembled into fibrillarnetworks to form a gel in THF induced by water, which is due to the hydrophobicinteraction of the oleanane skeleton and the balance between a tendency to dissolve anda tendency to aggregate. The supramolecular gel stability and morphology weresensitively affected by addition of complementary uracil derivatives through cleavingthe intergelator hydrogen bonds.As our continuous work, we develop a new kind of self-assembly molecules withtripeptide and triterpenoids to impart non-covalent bond association andbiocompatibility. These two molecules can form organogels in aromatic solvents andcould selectively gelate aromatic solvents from water. Furthermore, the xerogelsprepared from the organogels showed a striking property of adsorbing dyes such asrhodamine6G and acriavine. Additionally, it was also found that the aggregation formof self-assembled fibrillar networks result in a remarkable increase of its basicity byemploying different pH-indicator dyes. The new mono-and bis-triterpenoid derivatives linked by the connecting structurescontaining benzene rings and amide structures have been prepared, which could gelsome of the aromatic solvents and DMSO separately.1H NMR measurements revealedthat hydrogen bonding is an important driving force for the formation of the gelnetworks. It is proposed that the loose packing arrangement within the aggregates of thebis-triterpenoid derivatives resulted in the more chiral property of the assembly. Finally,the nanofibers in the organogel of DMSO were exploited as template to synthesize goldnanoparticles (AuNPs) and generate new gel-nanoparticle hybrid materials.