Design And Synthesis Of Novel Cytochrome Bc₁ Complex Q₀ Site Inhibitors

Recently, fungicides, which were based on the Qo site of mitochondrial cytochrome bc1 complex target, have been numerous varieties and developed rapidly. Especially for the strobilurins, they are a new generation of fungicides which have the most development potential and extremely market vitality. However, the resistance problem of fungicides has became more and more serious result from their long-term use. This has begun to restrict the development of this kind of inhibitors. Therefore, it is very necessary to design and synthesize of novel inhibitors, which are high activity, low resistance, high security, base on the Qo site of mitochondrial cytochrome bc1 complex target.According to the bioisosterism and the connecting principle of actively biological groups, we make high efficiency, broad spectrum and commercial fungicide Famoxadone and unique mechanism natural inhibitor Stigmatellin as lead compounds, and designed and synthesized a total of 59 Qo site inhibitors of bc1 complex with six types of novel structures in this paper, which are never reported in literatures. And we also test their biological activity. The specific research works are as follows:1. The advancement of structures and function of cytochrome bc1 complex were summarized. Then the main categorization, biochemical mode of action and resisance risk were briefly reviewed.2. Fifty-nine Qo site inhibitors of bc1 complex were designed and synthesized in this paper. All novel compounds are characterized by 1H NMR,13 C NMR and HRMS.3. At present, some compounds bioactivity assays are testing. The results indicated that most of compounds displayed poor fungicidal activity against tested fungi at the concentration of 200 or 100 mg·L-1. However, a few compounds performed some bactericidal activity. As for the Famoxadone derivatives, at the concentration of 200 mg·L-1, compounds Ⅰ a, Ⅰ b showed 50% and 40% fungicidal activity against Pseudoperonospora cubensis respectively. Moreover, at the concentration of 100 mg·L-1, compound Ⅱh showed 63% fungicidal activity against Rhizoctonia solani, which was better than that of famoxadone. And for the Stigmatellin derivatives, at the concentration of 200 mg·L-1, compounds Ⅳdc, Ⅴbc displayed 17% and 23% fungicidal activity against Rhizoctonia solani respectively, and compounds Ⅴbc,Ⅴbk showed 20% and 30% fungicidal activity against Sphaerotheca fuligenea respectively, which was better than that of famoxadone.4. Bioactivity assays of all compounds were tested against (porcine bc1) cytochrome bc1 complex in vitro and the IC50 values were determined by kinetic characterization. As for Famoxadone derivatives, many compounds showed significant inhibitory activity in vitro, such as, compounds Ⅰ a-e, Ⅱf, Ⅱg, Ⅱi, Ⅱj, Ⅱn inhibitory activities had reached the level of nanomolar. And the inhibitory activities of compounds Ⅰ c, Ⅰ d, Ⅱ i were close to that of contrast compoud Famoxadone (IC50= 3.90 nM). Furthermore, compound Ⅱn almost showed comparable activity (IC50= 3.10 nM) with that of Famoxadone.As for Stigmatellin derivatives, many compounds also showed significant inhibitory activity in vitro, such as, compounds Ⅳad, Ⅳaf, Ⅳah, Ⅳdb, Ⅳdc, Ⅴab, Ⅴaa, Ⅴba, Ⅴbb, Ⅴbc, Ⅴbf, Ⅴbg inhibitory activities have reached the level of nanomolar. And the inhibitory activities of compounds Ⅴbj, Ⅴbm, Ⅴbo, Ⅴbg were cmparable with that of Famoxadone.5. The implementation of structure-activity relationship study of Famoxadone derivatives and Stigmatellin derivatives offered important clues for further optimization of novel bc1 inhibitors.