Synthesis and in Vitro Antifungal Activities of Novel Benzamide Derivatives Containing a Triazole Moiety

The study reported the synthesis and antifungal activities in vitro against six phytopathogenic fungi of 17 novel N-[2-hydroxy-3,3-dimethyl-2-[(1H-1,2,4-triazol-1-yl)methyl]butyl]benzamide derivatives. All the target compounds were synthesized and elucidated by means of MS, high resolution (HR)-MS, IR, (1)H- and (13)C-NMR analysis. The results showed that almost all the derivatives exhibited good activities against each of the tested fungi at the concentration of 50 µg/mL. Among them, 6h displayed excellent activity against Alternaria alternata with the median effective concentration value (EC50) of 1.77 µg/mL, superior to myclobutanil (EC50=6.23 µg/mL), a commercial fungicide with broad-spectrum bioactivities for plant protection and high-efficiency. Compound 6k showed the broadest antifungal spectrum, demonstrating positive activities against the corresponding fungi with EC50 values ranging from 0.98 to 6.71 µg/mL. Furthermore, 6e to 6i revealed good activities against Alternaria solani with EC50 values of 1.90, 4.51, 7.07, 2.00 and 5.44 µg/mL, respectively. The preliminary analysis of structure-activity relationship (SAR) demonstrated that the presence of F or Cl on the benzene ring remarkably improved the activity, while the introduction of 4-OMe or CF3 group decreased the activity in varying degrees. Thus, the present results strongly suggest that N-[2-hydroxy-3,3-dimethyl-2-[(1H-1,2,4-triazol-1-yl)methyl]butyl]benzamide derivatives should be promising candidates for the development of novel antifungal agents in the effective control of phytopathogenic fungi.