Synthesis Of Some Novel Antimicrobial Agents With Maleimide Structure And Studies Of Their Antifunfal Activities

Plant pathogenic fungi are the most important factors of causing plant diseases. There about70%plant diseases are caused by the fungi, which has resulted in a large loss to world’s agricultural economy. Sclerotinia sclerotiorum and Botrytis cinerea, as two representatives of plant pathogenic fungi with a large scope of host, are supposed to experience a certain latent period and are complex in origin and stubborn in pythogenesis. These two fungi are pathogenic fungi with high risk to plants, and are easy to exert resistance. All of these has contributed to the necessary to develop antimicrobial agent with high efficiency and low toxicity.Lots of studies show that compounds with maleic anhydride structure have great activities against S. sclerotiorum and B.cinerea. However, most of compounds with maleic anhydride structure are highly toxic and profoundly depend on pH. For the purpose of solving these two shortcomings of maleic anhydride, we modify the compounds with maleic anhydride structure by two steps method to synthesize17dimethylmaleimides. 17compounds’ antifungal activities against S. sclerotiorum and B. cinerea by the mycelium growth rate method were also investigated. The results indicate that almost all the compounds have considerable antifungal activities against S. sclerotiorum and B. cinerea in vitro. The antimicrobial effect against S. sclerotiorum of ten maleimide derivatives (18a,18c,18d,18e,18i,18j,18m,18n,18p and18q) are better than dicloran (a standard aromatic fungicide) as the standard of minimum inhibitory concentration (MIC), among which, the inhibiting rate of N-(3,5-dichlorophenyl)-3,4-dimethy lmaleimide and N-(3,4,5-trifluoro-phenyl)-3,4-dimethylmaleimide both with a concentration of50μg/mL towards S. sclerotiorum mycelium have reached to94.5%and100.0%, respectively. The compounds18a,18h,18n and18q have a similar MIC with dicloran towards B. cinerea mycelium, with MIC ranging from0.1to1.0μg/mL. Moreover, research has showed that the inhibiting activity of N-alkyl-maleimides towards these two fungi increase first, then decrease, along with the enhancement of nonpolarity of carbochain.In this paper, the protecting effect of173,4-dimethylmaleimides to the in vitro leaves infected by S. sclerotiorum and B. cinerea have also been investigated. The result shows that the entire protecting effect concentrations of N-(3,5-dichlorophenyl)-3,4-dimethylmaleimide and N-(3,4,5-trifluorophenyl)-3,4-dimethylmaleimide are200and500μg/mL respectively, therefore, both compounds present a better protecting effect than dicloran (600μg/mL). And their entire protecting effect concentrations towards in vitro leaaves affected by B. cinerea are800and1000μg/mL, respectively. In conclusion, maleimides is promising for application in the concerned areas and has a huge potential to be developed as a novel anti-fungi agents.Research of maleimides’ activities against S. sclerotiorum and B. cinerea in this paper, to provide a foundation for further studying structure-activity relationship of maleimides and for guiding modification on maleimide. This has important theoretical and scientific significance for developing a new antifungal agent.