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BACKGROUND: The natural product paeonol is a rich and sustainable natural bioresource, and its derivatives have various unique biological efficacy. As is well known, Schiff bases are a class of organic compounds with a wide range of biological activities, including anti‐fungal, insecticidal, anti‐viral, and nematicidal. RESULTS: To discover biorational natural product‐based pesticides, nine intermediates (2–10), 12 sulfonylhydrazones (11a–11c, 12a–12c, 13a–13c, and 14a–14c) and 20 benzylidene hydrazones (18a–18r, 19a, and 20a) were synthesized by structural modification of paeonol, and their structures were characterized by proton nuclear magnetic resonance (1H NMR), carbon‐13 (13C) NMR, and high‐resolution mass spectrometry (HRMS). The stereochemical configurations of compounds 14a, 18d, and 18r were unambiguously confirmed by single‐crystal X‐ray diffraction. Furthermore, bioactivities of these compounds as anti‐oomycete, anti‐fungal, and nematicidal agents against three serious agricultural pests, Phytophthora capsici, Fusarium graminearum, and Heterodera glycines were evaluated. Among all tested compounds: (i) compound 7 exhibited promising anti‐oomycete against Phytophthora capsici, with a half maximal effective concentration (EC50) value of 15.81 mg L−1; (ii) compounds 2, 7, 10, and 19a displayed promising anti‐fungal against F. graminearum, with EC50 values of 12.22, 14.72, 23.39, and 33.10 mg L−1, respectively; (iii) ten compounds (12a–12c, 14c, 18g–18j, 18m, and 19a) showed significant nematicidal activity against H. glycines, with median lethal concentration (LC50) values all less than 30.00 mg L−1. Especially for compound 18g, its LC50 value is the smallest, at 12.65 mg L−1. CONCLUSION: The research results indicate that introducing nitro groups at the C5 position of paeonol, or introducing halogens at both C5 and C3 positions, can significantly enhance its biological activity against Phytophthora capsici, F. graminearum, and H. glycines. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Using ursolic acid (UA) as the lead compound, thirteen UA ester derivatives (3 and 7a-l) were synthesized by modifying their C-3 and C-28 positions, respectively, and their structures were well characterized by 1H NMR, 13C NMR, HRMS and melting points. Furthermore, we evaluated the anti-oomycete and anti-fungal activities of these compounds against Phytophthora capsici and Fusarium graminearum in vitro. The results showed that compound 7h exhibited prominent anti-oomycete and anti-fungal activities, and the median effective concentration (EC50) values of 7h against P. capsici and F. graminearum were 70.49 and 113.21 mg/L, respectively. This study suggested that the anti-oomycete and anti-fungal activities of esters synthesized by introducing acyloxy group at C-3 position of UA was more conspicuous than that of esters synthesized by introducing benzyloxy group at C-28 position. This result will pave the way for further modification of UA to develop potential new fungicides. [ABSTRACT FROM AUTHOR]

Cinnamic acid and geraniol are two well-known antifungal natural products and widely applied in food and cosmetics industries. To discover novel natural product-based fungicide candidates with more potent activity and good ecological compatibility for the management of plant diseases, a series of cinnamic acid-geraniol hybrids were prepared by means of molecular hybridization and their chemical structures were well confirmed by spectral analysis. The antifungal activities of the target compounds against three phytopathogenic fungi Fusarium graminearum, Gaeumannomyces graminis (Sacc.) Arx et Oliver var. tritici (Sacc.) Walker, and Valsa mali were evaluated. Among them, compounds 5 e and 5 f showed the remarkable antifungal activity against G. graminis with the EC 50 values of 82.719 and 91.828 μg/mL, respectively; while compounds 5 f and 6 b exhibited the obvious antifungal activity against V. mali. It suggested that compound 5 f can be further optimized for the design of novel broad-spectrum fungicide molecules as the secondary lead compound. In addition, some interesting structure-antifungal activity relationships were obtained. This work will provide some reference and guidance for the further discovery of novel fungicide candidates based on cinnamic acid and geraniol., (© 2024 Wiley-VHCA AG, Zurich, Switzerland.)

Oleanolic acid is a pentacyclic triterpenoid extracted and isolated from the fruit of plants in the Ligustrum lucidum Ait. in the family Oleaceae. To discover biorational natural product-based pesticides, a series of oleanolic acid derivatives containing anhydride active skeletons were prepared by ingeniously introducing an active acyloxy group at its C-28 carboxyl position, and their structures were well characterized by 1 H-NMR, 13 C NMR, HRMS, and m.p. The stereochemical configuration of compound 8 e was confirmed using single-crystal X-ray diffraction. Furthermore, bioactivities of these compounds as anti-oomycete and anti-fungal agents against two serious agricultural pests, Phytophthora capsici (P. capsici) and Fusarium graminearum (F. graminearum) we assessed. Amongst evaluated compounds, 1) Compounds 8 h and 8 j displayed significant anti-oomycete against P. capsici, with EC 50 values of 54.73 and 65.15 mg/L, respectively. 2) The target compounds have obvious selectivity, and their anti-oomycete activity is significantly better than their anti-fungal activity. 3) Interestingly, there are significant differences in the structure-activity relationship of different substituents or the same substituent at different positions anti-oomycete and anti-fungal against P. capsici and F. graminearum, respectively. The study provides an idea for further exploring the bioactivities of 28-acyloxyoleanolic acid derivatives, and develops the application of 28-acyloxyoleanolic acid derivatives containing anhydride in agriculture., (© 2024 Wiley-VHCA AG, Zurich, Switzerland.)

In order to explore novel natural product-based anti-oomycete agent, ten 2-acyloxyhinokitiol derivatives ( 5a-j ) were designed and synthesised, and structurally confirmed by 1 H NMR, 13 C NMR, HRMS, and melting point. The stereochemical configuration of compound 5f was unambiguously confirmed by single-crystal X-ray diffraction. Furthermore, we evaluated the target compounds 5a-j as anti-oomycete activity against a serious agricultural disease of Phytophthora capsici . Among the ten hinokitiol ester derivatives tested, four compounds 5d , 5g , 5h and 5j had anti-oomycete activity higher than the positive control zoxamide (EC 50 = 23.59 mg/L), and the EC 50 values of 18.90, 20.62, 13.61 and 21.29 mg/L, respectively. Especially compound 5h exhibited the best anti-oomycete activity against P. capsici with EC 50 value of 13.61 mg/L. Overall, the anti-oomycete activities of 2-acyloxyhinokitiol derivatives is higher than that of 2-sulfonyloxyhinokitiol derivatives. The results laid a good foundation for the subsequent synthesis of hinokitiol ester derivatives with significant anti-oomycete activity.

Background: Developing high-efficiency and low-risk small-molecule green fungicide is the key to effective control of the plant pathogenic oomycetes. Indole is an important raw material for drug synthesis. Due to its unique structural skeleton, indole, and its derivatives have exhibited a wide range of biological activities. However, a study on the synthesis of novel indole derivatives as fungicidal agents against Phytophthora capsici has not yet been reported., Methods: The important intermediates 2a-c and 3a-c were synthesized in high yields by Vilsmeier- Haack and Knoevenagel reactions with indole as the lead compound. Furthermore, different substituted benzenesulfonyl groups were introduced into the NH position of the indole ring, and twelve indole derivatives (I-a-l) were prepared. Their structures were well characterized by 1 H NMR, HRMS, and melting point., Results: The results showed that 2-[( N -(4-nitrobenzenesulfonyl)-indole-3)-methylene]-diethyl malonate (I-d) and 2-[( N -(4-nitrobenzenesulfonyl)-5-cyanoindole-3)-methylene]-diethyl malonate (I-l) showed more anti-oomycete activity against P. capsici than the commercialized fungicide zoxamide, with corresponding EC 50 values of 26.53, 23.48 and 28.16 mg/L, respectively, and the protective effect of the compounds against P. capsici in vivo further confirmed the above results., Conclusion: The preliminary structure-activity relationship showed that the formyl group modification at the C-3 position of the indole ring was acceptable, and the different anti-oomycete activities of R 1 and R 2 were significantly different, with R 1 being 5-CN > H > 6-Me, and R 2 being 4-NO 2 > 3-NO 2 , H > 4-Me., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)