Discovery of N-((2-Arylthiazol-4-yl)methyl)oxazole-5-carboxamide Derivatives as SDHi for Fungicidal Candidates

A series of oxazole-5-carboxamide derivatives were designed as succinate dehydrogenase (SDH) inhibitors and synthesized, characterized, and evaluated for their fungicidal activities. Among these compounds, SEZA18 and SEZC7 displayed 0.17 and 0.50 mg/L EC50 values against Magnaporthe grisea in vitro, respectively, whose anti-M. grisea activities were closed to prochloraz (0.15 mg/L) and surpassed hymexazol (45.5 mg/L). Moreover, SEZA18 and SEZC7 exhibited 45.3 and 49.5% protective effects against M. grisea at the dose of 200 mg/L in vivo, whose preventive effects were about double times less than that of azoxystrobin (93%). In addition, SEZA14 possessed an EC50 value of 2.33 mg/L against Penicillium digitatum in vitro and showed 77.9% prevention effects from P. digitatum at the dose of 100 mg/L in a potted experiment, whose fungicidal activity was comparable to that of boscalid (75.5%). SEZC7 demonstrated SDH inhibitory activity (IC50 = 16.6 μM), exhibiting activity levels similar to those of boscalid (IC50 = 12.9 μM). Molecular docking results further revealed that SEZA14, SEZA18, SEZC7, and boscalid possessed a mode of action similar to that of SDH. Transcriptome analysis suggested that C7 interfered with the energy metabolism by inhibiting SDH activity, thereby affecting cellular sugar metabolism processes of M. grisea. In summary, our finding gave SDH inhibitors featuring novel structures, which provided a potential candidate for the management of plant pathogenic fungi.

Scaffold-Hopping Approach To Identify New Chemotypes of Dimpropyridaz

Dimpropyridaz is a pyrazole carboxamide insecticide with a novel mode of action, currently under worldwide development by BASF, providing excellent activity against sucking pests. A series of dimpropyridaz analogues were designed to investigate the impact of bioisosteric heterocyclic replacements on the biological activity and molecular properties. Focus was given to prepare analogues where the 4-pyridazinyl moiety was replaced by 5-pyrimidinyl, 2-pyrimidinyl, 3-pyridazinyl, and 2-pyrazinyl groups. Five different synthetic routes were developed for the preparation of these analogues, delivering the target compounds in moderate to good yields. We explained some aspects of the observed structure-activity relationship by a density functional theory (DFT) calculation and DFT-derived Multiwfn and VMD program models. These findings provide first insights into the important role of the 4-pyridazinyl heterocyclic moiety in the pyrazole carboxamide insecticide chemical class and the mechanism of action of dimpropyridaz.

Design, Synthesis, and Bioactivity Evaluation of New Thiochromanone Derivatives Containing a Carboxamide Moiety

In this study, using the botanical active component thiochromanone as the lead compound, a total of 32 new thiochromanone derivatives containing a carboxamide moiety were designed and synthesized and their in vitro antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas oryzae pv. oryzicolaby (Xoc), and Xanthomonas axonopodis pv. citri (Xac) were determined, as well as their in vitro antifungal activities against Botryosphaeria dothidea (B. dothidea), Phomopsis sp., and Botrytis cinerea (B. cinerea). Bioassay results demonstrated that some of the target compounds exhibited moderate to good in vitro antibacterial and antifungal activities. In particular, compound 4e revealed excellent in vitro antibacterial activity against Xoo, Xoc, and Xac, and its EC50 values of 15, 19, and 23 μg/mL, respectively, were superior to those of Bismerthiazol and Thiodiazole copper. Meanwhile, compound 3b revealed moderate in vitro antifungal activity against B. dothidea at 50 μg/mL, and the inhibition rate reached 88%, which was even better than that of Pyrimethanil, however, lower than that of Carbendazim. To the best of our knowledge, this is the first report on the antibacterial and antifungal activities of this series of novel thiochromanone derivatives containing a carboxamide moiety.