A total of 22 quinazoline thioether derivatives incorporating a 1,2,4-triazolo­[4,3-a]­pyridine moiety were designed, synthesized, and evaluated as antimicrobial agents in agriculture. Among these compounds, the chemical structure of compound 6l was further confirmed via single-crystal X-ray diffraction analysis. The bioassay results revealed that some of the compounds possessed noticeable in vitro antibacterial activities against the tested phytopathogenic bacteria. For example, compounds 6b and 6g had EC50 values as low as 10.0 and 24.7 μg/mL against Xanthomonas axonopodis pv. citri (Xac), respectively, which were significantly better than that of the commercial agrobactericide bismerthiazol (56.9 μg/mL). Particularly, compound 6b was also found to be capable of suppressing the pathogenic bacterium Xanthomonas oryzae pv. oryzae (Xoo) approximately 12-fold more potent than control bismerthiazol, in terms of their EC50 values (7.2 versus 89.8 μg/mL). Importantly, the most active compound 6b turned out to be one with the highest hydrophilicity and the lowest molecular weight within the series. In vivo bioassays further showed the application prospect of 6b as a promising plant bactericide for controlling Xoo. Additionally, in vitro antifungal activities of these compounds were also evaluated at the concentration of 50 μg/mL. Overall, the present study demonstrated the potential of 1,2,4-triazolo­[4,3-a]­pyridine-bearing quinazoline thioether derivatives as efficient agricultural antibacterial agents for crop protection.

No abstract

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.

No abstract

A series of novel quinazolin-4-one derivatives (7a-7n) bearing the 7-oxo-1,2,4-triazolo[1,5-a]pyrimidine moiety were designed, synthesized and evaluated for their inhibition activities against phytopathogenic bacteria and fungi in vitro. All of the target compounds were fully characterized through [Formula: see text] NMR, [Formula: see text] NMR, HRMS and IR spectra. Among these compounds, the structure of compound 7e was unambiguously confirmed via single-crystal X-ray diffraction analysis. The turbidimetric assays indicated that compounds 7b, 7d, 7g, 7k and 7n exhibited much more potent inhibition activities against the pathogen Xanthomonas oryzae pv. oryzae (Xoo), relative to control Bismerthiazol. Moreover, antibacterial activities of compounds 7j, 7k and 7n against the pathogen Xanthomonas axonopodis pv. citri (Xac) were comparable to that of control Bismerthiazol. As for the pathogen Ralstonia solanacearum (Rs), only compounds 7g and 7i demonstrated inhibition activities similar to control Thiadiazole-copper. Moreover, this class of compounds did not display inhibition activity against three fungi tested. The above findings indicated that quinazolin-4-one derivatives containing the 7-oxo-1,2,4-triazolo[1,5-a]pyrimidine moiety have a potential as promising candidates for the development of new and more efficient agricultural bactericides.