Synthesis and antimicrobial evaluation of novel 1,2,4-triazole thioether derivatives bearing a quinazoline moiety

A series of structurally novel 3-thioether-1-(quinazolin-4-yl)-1H-1,2,4-triazol-5-amine derivatives (7a-7r) were designed and synthesized based on a pharmacophore hybrid approach, and screened for their antibacterial and antifungal activities in vitro. All the target compounds were fully characterized through [Formula: see text]H NMR, [Formula: see text]C NMR and HRMS spectra. Among them, the structure of compound 7b was further confirmed via single-crystal X-ray diffraction analysis. The obtained results indicated that several target compounds demonstrated notable inhibition activities against tested phytopathogenic bacteria, using a turbidimetric method. For example, compounds 7d, 7g and 7i exhibited EC[Formula: see text] (half-maximal effective concentration) values of 46.9, 47.8 and 43.2 µg/mL, respectively, against the bacterium Xanthomonas axonopodis pv. citri (Xac), which were more potent than commercial agrobactericide Bismerthiazol (56.9 µg/mL). Moreover, EC[Formula: see text] values of compounds 7a and 7h were found to be 81.6 and 93.1 µg/mL, respectively, against the bacterium Ralstonia solanacearum (Rs), being over twofold more active than commercial agrobactericide Thiodiazole-copper (189.6 µg/mL). Finally, some compounds displayed a certain degree of inhibition activity against tested phytopathogenic fungi at 50 µg/mL.