Synthesis and evaluation of imidazo[1,2-a]quinoxaline derivatives as potential antifungal agents against phytopathogenic fungi

Synthesis and antifungal activities of small molecule arylthiazolamine derivatives

Developing new fungicides to compensate for the deficiencies of existing fungicides resistance in phytopathogenic fungi is a research hotspot in the field of pesticides. Aiming to discover novel template small molecules with excellent antifungal activity, thirty-eight arylthiazolamine derivatives were synthesized through bromination, cyclization, halogenation, and acylation reactions. The synthesized compounds were screened for antifungal activity against ten typical fungal pathogens, and some halogenated arylthiazolamines and amides exhibited excellent broad-spectrum antifungal activity, especially compounds 4m (3.96-47.76 μg/mL), 5k (0.10-7.70 μg/mL) and 5n (2.08-11.21 μg/mL). Among them, compound 5k provided comparable protection and curative effects to chloroticonil and boscalid against B. dothidea and V. mali infection in apple and apple tree branches, respectively, and it could exert antifungal effects by inhibiting the differentiation of mycelium spores, spore germination, and bud tube growth. This study provides high-efficiency and inexpensive candidate compounds for managing of diseases caused by plant pathogenic fungi.

Design and synthesis of some novel structurally diverse thiochroman derivatives as fungicides against phytopathogenic fungi

BACKGROUND

Plant diseases infected by pathogenic fungi have a devastating effect on global agricultural and food industry yields. The development of novel, environmentally friendly, and efficient fungicides is an important technique for preventing and combatting phytopathogenic fungi.

RESULTS

Herein, 99 thiochroman-based derivatives containing hydroxyl, sulfoxide, sulfone, carbonyl, double bond, amino, imine, oxime, oxime ester, and amide moieties were synthesized. The antifungal activities of the target compounds against ten typical phytopathogenic fungi were also investigated. The bioassay results illustrated that most of the target compounds exhibited moderate to excellent antifungal effects against the tested fungi in vitro. Among these, thiochroman-oxime derivatives (12a-12m) exerted a promising inhibition effect, especially against Fusarium solani, Fusarium graminearum, Valsa mali, and Botrytis cinerea strains. Furthermore, the compounds 12f and 12g markedly suppressed the spore germination germ and tube growth. At the same time, they exerted excellent protective effects against potatoes infected by F. solani, making them superior to commercial fungicides Hymexazol and Chlorothalonil. Notably, the compounds 12d and 12f also showed excellent protective effects against cherry tomatoes infected by B. cinerea. Further mechanistic studies revealed that compound 12f exerted an antifungal effect by overtly altering the mycelium structure and remarkably increasing cell membrane permeability. Fortunately, the excellent bioactive compounds showed good safety against human hepatic cell lines (WRL-68). The preliminary structure-activity relationship analysis revealed that the introduction of hydroxyl or oxime fragments at the thiopyran ring might be significantly beneficial to antifungal activity.

CONCLUSION

This study provides thiochroman compounds that can be used in the development of novel botanical fungicides for the management of phytopathogenic fungi. © 2024 Society of Chemical Industry.

Design and Synthesis of Novel Phthalide Derivatives containing 1,3,4-Oxadiazole/1,2,4-Triazole Units as Potential Antifungal Agents

Four series of novel 1,3,4-oxadiazole/1,2,4-triazole hybrids of phthalide derivatives were designed and synthesized to search for novel potential antifungal agents. Preliminary antifungal activity assay results showed that compounds 4 a, 4 b, 4 m, 5 b, 5 f, 5 h, and 7 h exhibited moderate to excellent inhibitory activity against some phytopathogenic fungi. Among them, compound 5 b displayed the most outstanding antifungal effects against V. mali and S. sclerotiorum, with the EC50 mean of 3.96 μg/mL and 5.60 μg/mL, respectively, which was superior to those of commercial fungicides hymexazol and chlorothalonil. Furthermore, compound 5 b could completely suppress the spore germination of V. mali at a concentration of 10 μg/mL. Finally, molecular docking revealed that the potential target for the antifungal activity of compound 5 b was succinate dehydrogenase (SDH). This research provides novel candidate compounds for the prevention of phytopathogenic fungi.