Design and synthesis of novel 3-(thiophen-2-yl)-1,5-dihydro-2H-pyrrol-2-one derivatives bearing a hydrazone moiety as potential fungicides

Design, Synthesis, Antifungal Activity, and 3D-QASR of Novel Oxime Ether-Containing Coumarin Derivatives as Potential Fungicides

Structural modification of natural products is an effective approach for improving antifungal activity and has, therefore, been used extensively in the development of new agrochemical products. In this work, a series of novel coumarin derivatives containing oxime ether structures were designed, synthesized, and evaluated for antifungal activity. Some of the designed compounds exhibited promising antifungal activities against tested fungi, and compounds 4a, 4c, 5a, and 6b had EC50 values equivalent to those of commercial fungicides. Compound 6b was the most promising candidate fungicide against Rhizoctonia solani (EC50 = 0.46 μg/mL). In vivo antifungal bioassays suggested that compounds 5a and 6b could serve as novel agricultural antifungals. Furthermore, microscopy demonstrated that compound 6b induced the sprawling growth of hyphae, distorted the outline of cell walls, and reduced mitochondrial numbers. Additionally, the effects of the substituent steric, electrostatic, hydrophobic, and hydrogen-bond fields were elucidated using an accurate and reliable three-dimensional quantitative structure-activity relationship (3D-QSAR) model. The results presented here will guide the discovery of potential novel fungicides for plant disease control in agriculture.

Novel carboxylated pyrroline-2-one derivatives bearing a phenylhydrazine moiety: Design, synthesis, antifungal evaluation and 3D-QSAR analysis

Aiming to discover novel high-efficient antifungal leads that possess an innovative action mechanism, twenty-three carboxylated pyrroline-2-one derivatives, bearing a phenylhydrazine moiety, were rationally designed and firstly prepared in this letter. The in vitro bioassays showed that most of the compounds possessed excellent antifungal effects with the EC₅₀ values of less than 1 μg/mL against the phytopathogenic fungi Fusarium graminearum (Fg), Botrytis cinerea (Bc), Rhizoctonia solani (Rs) and Colletotrichum capsici (Cc). The further bioassays showed that the compound 6u showed the comparable in vivo control effect with carbendazim against fusarium head blight and rice sheath blight. The 3D-QSAR model revealed the pivotal effects of a bulky electron-donating group at the 1-position of pyrrole ring, a bulky electron-withdrawing group at the 4-position of phenyl ring and a small alkyl at the carbonate group on the anti-Rs activities of target compounds. The abnormal mycelial morphology and delayed spore germination were observed in the treatments of compound 6u. Given the excellent and broad-spectrum antifungal effects the target compounds have, we unfeignedly anticipated that the above finding could motivate the discovery of high-efficient antifungal leads, which might possess an innovative action mechanism against phytopathogenic fungi.

Synthesis and antimicrobial properties of steroid-based imidazolium salts

Imidazolium salts reveal interesting biological properties, especially regarding antitumor and antimicrobial activities. Two series of imidazolium salts based on steroids were obtained in an efficient and convenient synthesis. They were biologically tested to evaluate their antibacterial and antifungal properties. The activities of new salts, especially in relation to Gram-positive bacterial strains are comparable to the activities of known antibiotics. The most promising activity was that against C. albicans, which exceeded the antifungal activity of commonly used drugs. Some of the new salts exhibited improved antifungal activities against phytopathogenic fungi: B. cinerea and C. beticola. Our research showed that new compounds could be potentially useful as antifungal antibiotics or inhibiting agents against pathogenic fungi.

Novel chalcone derivatives containing a 1,2,4-triazine moiety: design, synthesis, antibacterial and antiviral activities

A series of novel chalcone derivatives containing the 1,2,4-triazine moiety were synthesized and their structures were confirmed by 1H NMR, 13C NMR and elemental analyses. Antiviral bioassays revealed that most of the compounds exhibited good antiviral activity against tobacco mosaic virus (TMV) at a concentration of 500 μg mL-1. The designated compound 4l was 50% effective in terms of curative and protective activities against TMV with 50% effective concentrations (EC50) of 10.9 and 79.4 μg mL-1, which were better than those of ningnanmycin (81.4 and 82.2 μg mL-1). Microscale thermophoresis (MST) also showed that the binding of compound 4l to coat protein (TMV-CP) yielded a K d value of 0.275 ± 0.160 μmol L-1, which was better than that of ningnanmycin (0.523 ± 0.250 μmol L-1). At the same time, molecular docking studies for 4l with TMV-CP (PDB code:1EI7) showed that the compound was embedded well in the pocket between the two subunits of TMV-CP. Meanwhile, compound 4a demonstrated excellent antibacterial activities against Ralstonia solanacearum (R. solanacearum), with an EC50 value of 0.1 μg mL-1, which was better than that of thiodiazole-copper (36.1 μg mL-1) and bismerthiazol (49.5 μg mL-1). The compounds act by causing folding and deformation of the bacterial cell membrane as observed using scanning electron microscopy (SEM). The chalcone derivatives thus synthesized could become potential alternative templates for novel antiviral and antibacterial agents.

Synthesis, antiviral and antibacterial activities and action mechanism of penta-1,4-dien-3-one oxime ether derivatives containing a quinoxaline moiety

A series of penta-1,4-dien-3-one oxime ether derivatives containing a quinoxaline moiety were synthesized, and their bioactivities and action mechanism were evaluated.

Design and synthesis of novel 2-(6-thioxo-1,3,5-thiadiazinan-3-yl)-N'-phenylacethydrazide derivatives as potential fungicides

A series of novel 2-(6-thioxo-1,3,5-thiadiazinan-3-yl)-N'-phenylacethydrazide derivatives were designed, synthesized and evaluated for their antifungal activities against Fusarium graminearum (Fg), Rhizoctonia solani (Rs), Botrytis cinerea (Bc) and Colletotrichum capsici (Cc). The bioassay results in vitro showed that most of the title compounds exhibited impressive antifungal activities against the above plant fungi. Particularly, the compounds 5c, 5f, 5g, 5i, 5m and 5p displayed desirable anti-Rs activities, with the corresponding EC₅₀ values of 0.37, 0.32, 0.49, 0.50, 0.46 and 0.45 µg/mL, respectively, which are superior to the positive control carbendazim (0.55 µg/mL). Further in vivo bioassay results showed that the anti-Rs activity of title compound 5f at 200 µg/mL reached 95.84% on detached rice leaves and 93.96% on rice plants. Featuring convenient synthesis, novel structures and desirable antifungal activity, these 2-(6-thioxo-1,3,5-thiadiazinan-3-yl)-N'-phenylacethydrazide derivatives could be further studied as the potential candidates of novel agricultural fungicides.