Synthesis of 1,2,3-Thiadiazole and Thiazole-Based Strobilurins as Potent Fungicide Candidates

Strobilurin
fungicides play a crucial role in protecting plants
against different pathogens and securing food supplies. A series of
1,2,3-thiadiazole and thiazole-based strobilurins were rationally
designed, synthesized, characterized, and tested against various fungi.
Introduction of 1,2,3-thiadiazole greatly improved the fungicidal
activity of the target molecules. Compounds 8a, 8c, 8d, and 10i exhibited a relatively
broad spectrum of fungicidal activity. Compound 8a showed
excellent activities against Gibberella zeae, Sclerotinia sclerotiorum, and Rhizoctonia cerealis with median effective concentrations
(EC50) of 2.68, 0.44, and 0.01 μg/mL, respectively;
it was much more active than positive controls enestroburin, kresoxim-methyl,
and azoxystrobin with EC50 between 0.06 and 15.12 μg/mL.
Comparable or better fungicidal efficacy of compound 8a compared with azoxystrobin and trifloxystrobin against Sphaerotheca fuliginea and Pseudoperonspera
cubensis was validated in cucumber fields at the same
application dosages. Therefore, compound 8a is a promising
fungicidal candidate worthy of further development.