Design, Synthesis And Biological Evaluation Of Novel Triazole Antifungal Derivatives

The incidence of systemic fungal infections has increased substantially over the past 30 years, especially in those individuals with immunocompromised hosts, such as patients undergoing anticancer chemotherapy or organ transplantion and patients with AIDS. Currently, systemic fungal infections are a common cause of morbidity and mortality in patients with haematological malignancies or those undergoing bone marrow transplantation. It is estimated that systemic fungal infections develop in 10% to 25% of patients with acute leukaemia and those receiving bone marrow transplantation. The case fatality rate exceeds 50% and is approximately 90% in aspergillosis, particularly in patients with persistent neutropenia. Therefore, there is an emergent need to develop novel antifungal agents with higher efficiency, broader spectrum and lower toxicity.Azoles are important class of antifungal agents that interferes with ergosterol biosynthesis by inhibiting a cytochrome P450 enzyme lanosterol 14a demethylase (CYP51), an essential enzyme in this pathway. This leads to the depletion of ergosterol and accumulation of C-14 methylated sterols and hence disruption of membrane functions. Triazole antifungal agents such as Fluconazole and Itraconazole now are the most widely used for the treatment of systemic fungal infections.In an effort to search for new potent, less toxic and broad spectrum antimycotics, 182 1-(1H-1,2,4-triazol-1-yl)-2-(2,4-difluorophenyl)-3-(4-(2,4-disubstitutedphenyl)-1 -piperazyl)-2-propanols were designed and synthesized according to the 3D structure and action mode of CYP51 and structure-activity relationships of the azole antifungal agents. All intermediates and title compounds were ascertained by means of 1HNMR, MS and IR. MICs of all title compounds were determined by the method recommended by the National Committee for Clinical Laboratory Standards(NCCLS) using RPMI1640 test medium. Ten fungi were used: Candida albicans ATCC76615,Cryptococcus neoformans ATCC32609,Candida parapsilosis,Candida tropicalis,Candida Krusei,Trichophyton rubrum,Fonsecaea compacta,Microsporum gypseum,Torulopsis glabrata and Aspergillus fumigatus. The results of preliminary antifungal test showed that all title compounds exhibited potent antifungal activities to a certain extent. Among them, Compounds B2, B3, B5, B10, B26, C4, C7, C16, D35 exhibited excellent in vitro antifungal activity against Candida albicans than Fluconazole, Itraconazole and Voriconazole (with the MIC80 values of 0.00097 mg·L-1 respectively) . The MIC80s of compounds B1, B6, B15, B17, B25, C1-C3, C6, C13, C17, C22, C23, D2, D5, D32, E1, E3 and E6 (with the MIC80 values of 0.0039 mg·L-1 respectively) are more than 1000 times lower than that of Fluconazole, 256 times lower than that of Itraconazole and 4 times lower than that of Voriconazole against Candida albicans in vitro. Compounds D4 showed strong activity against Aspergillus fumigatus than Fluconazole and Voriconazole, and 16 times higher than Itraconazole against Aspergillus fumigatus in vitro. Compounds E1, E4, E6 showed excellent activity against Aspergillus fumigatus than Fluconazole and Voriconazole, and equal activity to Itraconazole against Aspergillus fumigatus in vitro. Especially, some compounds such as B2, B3, B10, C4, C6, C7, D2, D5, E1, E6 exhibited strong activities against all fungi tested and worthy of being further studied.According to the basic discussion of structure-activity relationship of all triazole title compounds, we got the following conclusions:(1) The basic pharmacores in the scaffold of triazole antifungal derivatives such as triazole, 2,4-difluorophenyl and hydroxyl group are very important for their antifungal activity.(2) The introduction of fluorine atom and trifluoromethyl group in the position 2 of phenyl group connected with piperazyl will weaken the antifungal activities of title compounds.(3) Compounds containing amide group were more active against all isolates than those containing schiff's base side chain.(4) For the title compounds with an alkyl amide side chain, lengthening the side chain to some extent will enhance the antifungal activities of title compounds. And for those with a short alkyl amide side chain, the introduction of halide atom such as chlorine atom and fluorine atom will enhance the antifungal activity.For the title compounds with a benzamide side chain, the introduction of halide atom will excellently enhance the antifungal activity; especially the halide atom lies in the position 2 of the phenyl group.For the title compounds with a cinnamide side chain, the introduction of vinyl group weakened the antifungal activities.For the title compounds with a heterocyclic amide side chain, the introduction of furan group enhance the antifungal activity.In general, the basic conclusion for the QSAR of all title compounds showed that without substitution of position 2 in the phenyl group connected with piperazyl group is helpful for their antifungal activities. Secondly, introduction of a hydrophobic side chain in the position 4 in the phenyl group will enhance the antifungal activity to some extent. The further modification of title compounds is to introduce heterocyclic amide with more than one hetero-atom side chain to adjust the solubility to enhance the activity and broaden the antifungal spectrum.