Structural Modification of Saccharin Containing 2‐Aminothiazole As Potential Fungicidal Agents

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.

Design, synthesis, and antimicrobial evaluation of 2-aminothiazole derivatives bearing the 4-aminoquinazoline moiety against plant pathogenic bacteria and fungi

BACKGROUND

To find more effective agricultural antibiotics, a class of new 2-aminothiazole derivatives containing the 4-aminoquinazoline moiety were synthesized and evaluated for their antimicrobial properties against phytopathogenic bacteria and fungi of agricultural importance.

RESULTS

All the target compounds were fully characterized by 1 H NMR, 13 C NMR, and high-resolution mass spectrometry. The bioassay results showed that compound F29 with a 2-pyridinyl substituent exhibited an outstanding antibacterial effect against Xanthomonas oryzae pv. oryzicola (Xoc) in vitro, having an half-maximal effective concentration (EC50 ) value as low as 2.0 μg/mL (over 30-fold more effective than the commercialized agrobactericide bismerthiazol, with an EC50 value of 64.3 μg/mL). In addition, compound F8 with a 2-fluorophenyl group demonstrated a good inhibitory activity toward the bacterium Xanthomonas axonopodis pv. citri (Xac), around twofold more active than bismerthiazol in terms of their EC50 values (22.8 versus 71.5 μg/mL). Interestingly, this compound also demonstrated a notable fungicidal effect against Phytophthora parasitica var. nicotianae, with an EC50 value largely comparable with that of the commercialized fungicide carbendazim. Finally, mechanistic studies revealed that compound F29 exerted its antibacterial effects by increasing the permeability of bacterial membranes, reducing the release of extracellular polysaccharides, and triggering morphological changes of bacterial cells.

CONCLUSION

Compound F29 has promising potential as a lead compound for developing more efficient bactericides to fight against Xoc. © 2023 Society of Chemical Industry.

Structural Optimization, Fungicidal Activities Evaluation, DFT Study and Structure-Activity Relationship of Dopamine Derivatives with Benzothiazole Fragment from Polyrhachis dives

In our previous work, two dopamine derivatives with benzothiazole fragment were isolated and identified from Polyrhachis dives (P. dives). Based on their characteristic structure, we used them as lead compound to carry out structural optimization and subsequent fungicidal evaluation. Here 20 dopamine derivatives with benzothiazole fragment were designed and synthesized by a facile method, and their structures were characterized by 1 H-NMR, 13 CNMR and HMRS. In bioassays, most of the title compounds possess potential fungicidal activities against Altenaia alternala (A. alternala) and Botrytis cinerea (B. cinerea). Especially, (E)-N-(2-(benzo[d]thiazol-6-yl)ethyl)-3-(p-tolyl)acrylamide and (E)-N-(2-(benzo[d]thiazol-6-yl)ethyl)-3-(4-(trifluoromethyl)phenyl)acrylamide displayed 29.3 mg/L and 10.7 mg/L EC50 value against A. alternala, respectively, which possessed equivalent fungicidal activities level to hymexazol.