Synthesis of novel 1,2,4-triazole derivatives containing the quinazolinylpiperidinyl moiety and N-(substituted phenyl)acetamide group as efficient bactericides against the phytopathogenic bacterium Xanthomonas oryzae pv. oryzae

Abstract

A series of novel 1,2,4-triazole derivatives (7a–7p) containing the quinazolinylpiperidinyl moiety and N-(substituted phenyl)acetamide group were designed, synthesized and evaluated for their antimicrobial activities in vitro. These compounds were fully characterized by ¹H NMR, ¹³C NMR, HRMS and IR spectra. Notably, the structure of compound 7p was further confirmed through the single-crystal X-ray diffraction method. The obtained bioassay results indicated that most of these compounds exhibited good to excellent antibacterial activities against the rice bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo). For example, compounds 7e, 7g, 7n, 7l, 7i, 7k, 7a and 7h had EC₅₀ (half-maximal effective concentration) values of 34.5, 38.3, 39.0, 46.0, 47.5, 54.6, 55.0 and 58.2 μg mL⁻¹ against the bacterium, respectively, which were significantly lower than the control agent Bismerthiazol (85.6 μg mL⁻¹). Additionally, antifungal experiments demonstrated that all the compounds did possess weak inhibition capabilities against three phytopathogenic fungi at 50 μg mL⁻¹, except in the cases of compounds 7e and 7p against the fungus Gibberella zeae. The above experimental results proved that 1,2,4-triazole derivatives bearing both a quinazolinylpiperidinyl fragment and N-(substituted phenyl)acetamide unit are promising candidates for the development of new agricultural bactericides against the pathogenic bacterium Xoo, deserving further investigation in the future.