Design, Synthesis And Biological Evaluation Of Benzimidazole Derivatives

Benzimidazole, a heteroaromatic compound with two nitrigon atoms, shows biological acitivities due to it being a good bioisoster of guanine residue and other biomolecules. Benzimidazole ring is an important pharmacophore in drug discovery. It is commonly encountered in drugs and displays diversity of pharmacological activitiy such as antiulcer, antitumoral, antiparasitic, antibacterial, antiviral, anti-inflammatory, and anti-histamine activity. Therefore, benzimidazole derivatives have attracted the interest of various research groups, and the drug design based on benzimidazole will be an important way in drug discovery.The action mechanism of PPIs has been studied extensively. After PPIs are absorbed and rapidly transformed by an acid-induced, they could be intramolecular rearranged into the pharmacologically active entity-a cyclic sulphenamide. The cyclic sulphenamide opens and then binds covalently to one or more cysteine thiol groups （-SH） on the luminal surface of the H⁺,K⁺-ATPase, which leads to irreversible inhibition of this enzyme. As a result gastric acid secretion is suppressed. Recently, amount of evidence has indicated that the functional native enzyme in the membrane is an oligomer comprised of （αβ）2-protomers in H⁺,K⁺-ATPase. Some studies clearly demonstrated that the fully functional enzyme was present in the oligomer. We designed a series of bis-benzimidazole compounds according to these findings. Thirty desired compounds were prepared from benzidine through an eight-step process and the structure confirmation was studied through LC-MS and ¹H-NMR mothods. Anti-secretory test in histamine-induced rat model was used to screen lead compounds from bis-benzimidazoles. The maximal inhibitory rate of BP-8C reached 80 %. Other compounds also showed efficacy on the antisecretion and the preliminary QSAR was summarised.Hoechst 33258, a DNA minor groove binder with a bis-benzimidazole structure, showed its excellent cytotoxic activity by selectively binding to DNA and inhibiting topoisomerase I. Many research articles have reported derivatives of Hoechst 33258, such as ter-benzimidazole, symmetrical bis-benzimidazole. In this thesis, bis-benzimidazoles were developed as a type of novel derivatives of Hoechst 33258. Docking was performed to model the binding of BP-1A and DNA dodecamer d（CGCAAATTTGCG）. We found BP-1A adopted a concave shape, which exactly fitted into the convex DNA minor groove in the model. In addition, two hydrogen bonds between BP-1A and DNA are formed between benzimidazole NH group and AT base pairs. All these novel compounds were screened for antiproliferation activity on SKOV-3, HeLa, and BGC-823 cell lines in vitro. Some compounds showed aroundμM IC₅₀ activities in preliminary anti-tumor tests. For SKOV-3 cell line, BP-1A, BP-8A, and BP-9A inhibited cell proliferation below concentration of 10μM. For HeLa cell line, BP-3B, BP-8B, and BP-10B were as effective as cisplatin. For BGC-823, BP-4B, BP-8B, and BP-10B could inhibit cell proliferation with concentrations below 10μM.Although PPIs have made a milestone for treatment of peptic diseases, they are still far from ideal antisecretory agents. Chemical instability in solution, not full acid control and low oral bioavailibility are the shortcomings and limitations of current PPIs. Several patents and articles has focused on prodrugs of PPIs.We designed a series of N-glycosylomeprazole derivatives in order to increase the chemical stability of omeprazole in solution and improve its oral bioavailability. The thioether derivative of omeprazole was used as the starting material, and through N-glycosidation, oxidation, and hydrolysis, six novel omeprazole N-glucosides were synthesized. LC-MS was performed to assign the structures. Two omeprazole glycosides, Glc-ome and Rib-ome, were evaluated in gastric ulcer models of guinea pig and Shay rat, respectively. The gastric protective effect of Rib-ome was screened on gastric lesion mice model induced by ethanol and HCl-ethanol. Metabolism of Glc-ome and Rib-ome in rats was studied by UPLC-MS/MS and the metabolites were analysized. Pharmacological results showed Glc-ome and Rib-ome were as effective as sodium pantoprazole in gastric ulcer models, and Rib-ome was equally effective as sucralfate in the protection of gastric mucosa in the gastric lesion mice.Each omeprazole glycoside compound was consisted of many diastereoisomers due to several isomeric centers in these molecules. These isomers include tautomer of benzimidazole, syn-anti conformational isomer of glycosidic bond, R/S isomer of chiral sulfur atom. The separation of all diastereoisomers of Glc-ome was performed on RP-HPLC in this thesis. And the stereochemisty of these diastereoisomers was studied. ¹H-NMR, ¹³C-NMR, and NOESY methods were used in the confirmation of 5（6）-OCH₃ isomers. From the NOESY spectra, the syn-anti conformational isomers were clearly differentiated. OR and CD methods, and asymmetrical synthesis were performed to assign the absolute configurations of chiral sulfur atom. Interconversion of syn-anti conformational isomers of Glc-ome was observed in solution. The kinetic rates and thermodynamic rates of these interconversions were determined by HPLC, respectively.