Synthesis Of Novel Azole Compounds And Their Relational Antimicrobial Study

Azole compounds are an important type of nitrogen containing electron-rich aromatic heterocycles, and have extensive potential applications in medicinal, agricultural, chemical, supramolecular as well as materials sciences. Especially in medicinal field, azoles could easily interact with various enzymes and receptors in organisms through non-covalent interactions to exhibit broad biological activities like antibacterial, antifungal, antiviral, anticoagulant, anti-inflammatory, anticancer and antioxidant properties etc. With increasing number of azole containing medicinal drugs extensively used in clinic, more and more resistant bacteria have appeared which have attracted numerous attentions. Benzimidazole is a fused ring of imidazole with benzene, and possesses larger conjugated system and stronger electron transport abilities than imidazole and benzene, and which may have extensive potentiality in medicinal chemistry. Moreover, benzimidazoles may inhibit the synthesis of nucleic acids and proteins inside the bacterial cell wall, and then kill the bacterial strains or inhibiting their growths. Therefore, more and more efforts were directed to the researches of benzimidazole compounds to develop novel structural compounds with distinct action mechanisms from the well-known antimicrobial agents.Fluconazole as the first-line triazole-antifungal drug recommended by World Health Organization (WHO), has established an exceptional therapeutic record for Candida infections, and become the first choice in the treatment of fungal infections. However, extensive clinical use of fluconazole has resulted in increasing fluconazole-resistant C. albicans isolates. Moreover, fluconazole with low water solubility is not effective against invasive aspergillosis. All these promoted the further development of fluconazole to optimize its therapeutic indexes. In consideration of the researches of azole compounds, a series of novel azole compounds were designed, synthesized and evaluated their antimicrobial activities. The combination interactions of strong active compounds with clinical drugs were investigated, and the interactions with calf thymus DNA and human serum albumin were also studied. The preliminary structure-activity relationships were also discussed. The main work was summarized as follows:(1) Benzimidazole tertiary amine type of fluconazole analogues were first synthesized via multi-step reactions from commercially available o-phenylene diamine and chloroacetic acid. All the newly prepared compounds were characterized by 1H NMR,13C NMR, IR, MS and HRMS spectra. Bioactive assay manifested that most of the prepared compounds could effectively inhibit the growth of microorganism, and compounds containing benzyl groups were more active than alkyl ones. Particularly, compound II-5m exhibited good antimicrobial activities (MIC=8-32 μg/mL) and broad spectrum, and its combination with clinical drugs showed better antimicrobial efficiency with less dosage and broader antimicrobial spectrum than the separated use of them alone, and these combined systems were more sensitive to methicillin-resistant MRSA and Fluconazole-insensitive A. flavus. This would be hopeful for the treatment of multidrug-resistant infections.(2) During the procedure for the preparation of benzimidazole tertiary amine type of fluconazole analogues, a series of N-alkylated benzimidazole compounds were synthesized by changing feeding sequence. All the newly synthesized compounds were characterized by 1H NMR,13C NMR, IR, MS and HRMS spectra. Antimicrobial results demonstrated that the bis-trifluoromethyl benzimidazole Ⅲ-51 gave good activity against the tested microorganism. Notably, its anti-B. subtilis, anti-B. proteus, and anti-E. coli activities (MIC=16,16, and 8 μg/mL respectively) were twice as potent as the reference drug chloromycin. The combination of high bioactive compound Ⅲ-51 and its salt Ⅲ-7 with antibacterial chloromycin, norfloxacin or antifungal fluconazole respectively showed better antimicrobial efficiency with less dosage and broad antimicrobial spectrum than the separated use of them alone. Moreover, the interaction of compound Ⅲ-5I with calf thymus DNA revealed that this compound could effectively intercalate into DNA to form a compound Ⅲ-51-DNA complex that might block DNA replication and thereby exert good antimicrobial activity.(3) In the process for the preparation of tertiary amine benzimidazole derivatives, unexpected benzimidazolone IV-7a was obtained under mild reaction conditions for the first time by unique one-pot reaction via C-C cleavage from aminomethylene benzimidazole, and its precise structure was further manifested by X-ray diffraction measurement. In order to further investigate this reaction, important influential factors including base, temperature, solvent, water content, and molar ratio of substrates to this reaction were screened, and possibly mechanistic consideration was also discussed. This reaction might provide new synthetic method for the preparation of benzimidazolone compounds. The synthesized benzimidazolones were evaluated and some compounds especially compound IV-7a exhibited better bioactivities against the tested strains than clinical drugs chloromycin, norfloxacin, and fluconazole.(4) In consideration of the vital role of sulfonamides in clinic, a series of sulfonamide tertiary anine type of fluconazole analogues were expected to be designed and synthesized. However, the X-ray single-crystal structure showed that novel sulfonamide azoles were prepared via unique C-N cleavage of cyclic sulfonamides. The important influential factors including temperature, solvent and reaction time for this unique reaction were also investigated. This type of reaction might open a new directions for the cleavage of cyclic compounds. The newly synthesized compounds were characterized by 1H NMR,13C NMR, IR, MS and HRMS spectra. Bioactive assay indicated that some synthezied sulfonamide derivatives exhibited moderate inhibitory activity, and compound V-9d bearing 2-methyl-5-nitro imidazole moiety gave the best anti-P. aeruginosa efficiency in this series and was equivalent to chloromycin (MIC=16 μg/mL). The combination of sulfonamide azole V-9d with chloromycin, norfloxacin, or fluconazole respectively gave significant synergistic effects. Further research showed that compound V-9d could effectively intercalate into calf thymus DNA to form V-9d-DNA complex which might block DNA replication to exert their powerful antimicrobial activities. The transportation behavior of this compound by human serum albumin (HSA) demonstrated that the electrostatic interactions played major roles in the strong association of compound V-9d and HSA.