Design and synthesis of novel cylopentapyrazoles bearing 1,2,3-thiadiazole moiety as potent antifungal agents

Abstract

In drug-resistant phytopathogenic fungi, there has been extensive research on microbiological and antifungal drug development. In this study, a novel series of cylopentapyrazole bearing a 1,2,3-thiadiazole ring 2a-e were designed and synthesized according to the principle of combination of bioactive structures. Thus, we have employed a [3 + 2] cycloaddition with 4-methyl-[1,2,3] thiadiazole-5-carboxylic acid hydrazones 1a-e and cyclopentadiene ring. Novel synthesized compounds were identified with IR, H-1 and C-13 NMR, mass spectrometry and elemental analysis then, antifungal activities were assayed. Based on our study, a combination of the compounds 1a and 2b possess remarkable antifungal activity against Botrytis cinerea AHU 9424 with 100% inhibition. EC50 values were calculated by studying different doses in combinations with high inhibition rates. The combination of 1a + 2b has an EC50 value at 6.37 and 13.85 mu g/ml concentrations against B. cinerea and F. culmorum, respectively. The combination of compound 1a + 2b, having a cylopentapyrazole ring on the 1,2,3-thiadiazole backbone, shows promising fungicidal activity and deserves further development. Additionally, the homology model of the CYP51 enzyme that belongs to Fusarium moniliforme was generated using CYP51B (PDB ID: 6CR2), and molecular docking was performed using this homology model for each compound. The results of this study clearly indicate that these novel compounds can be identified as promising lead compounds and potential fungicidal agents in future.