Novel [1,2,4]-Triazolo[3,4-b]-[1,3,4]thiadizoles as Potent Pyruvate Kinase Inhibitors for Fungal Control

Abstract

To discover novel target-based fungicidal candidates, a molecular design model was established with a threedimensional (3D) structure of Rhizoctonia solani pyruvate kinase (RsPK) simulated with the AlphaFold 2 and YZK-C22 as a fungicidal lead. A series of novel [1,2,4]triazolo [3,4-b][1,3,4]thiadiazole derivatives were rationally designed, synthesized, evaluated for their fungicidal performance, and validated for their mode of action. The in vitro bioassays with R. solani indicated that compounds 5g, 5o, and 5z with an EC 50 value ranging from 1.01 to 1.54 μg/mL displayed higher fungicidal activity than the positive control YZK-C22 with its EC 50 of 3.14 μg/mL. Especially, 5o exhibited high potency and a broad spectrum against Alternaria solani, Botrytis cinerea, Cercospora arachidicola, Physalospora piricola, R. solani, and Sclerotinia sclerotiorum with its EC 50 value falling between 1.54 and 13.10 μg/mL. Like all positive controls, 5g, 5o, and 5z showed excellent in vivo growth inhibition against Pseudoperonospora cubensis at 200 μg/mL. Even though the PK enzymatic inhibition assay showed that 5o was approximately 2.6 times less active than YZK-C22 (IC 50 : 29.14 vs 11.15 μg/mL, respectively), the similar fluorescence quenching patterns of RsPK by 5o and YZK-C22, and the docking results of interactions between RsPK and 5o or YZK-C22 implied that they might share the similar binding site in the RsPK active pocket. Our studies suggested that 5o could be used as a potent fungicidal lead for further optimization. The results of comparative molecular field analysis (CoMFA) provided a direction for further molecular design.

CoMFA Directed Molecular Design for Significantly Improving Fungicidal Activity of Novel [1,2,4]-Triazolo-[3,4-b][1,3,4]-thiadizoles

“…The experimental procedures were modified according to the previously reported methods. ,, A mixture of thiocarbohydrazide (11 mmol) and compound 1 (10 mmol) in 20 mL of ethanol was refluxed for 2 h. After the reaction was completed (monitored by TLC with petroleum ether (60–90 °C fraction)/ethyl acetate (3:1–1:1, v/v)), the reaction mixture was concentrated and cooled, and the residue was obtained by removing the solvents and purified by column chromatography over silica gel to afford intermediates 2 .…”

Exploration of Fungicidal Activity and Mode of Action of Ferimzone Analogs

“…7 Later, isothiazole-purines and triazolo-thiadiazoles were designed and synthesized as pyruvate kinase inhibitors with higher fungicidal activity than YZK-C22. 8,9 Rice (Oryza sativa L.), one of the most widely cultivated crops in the world, is a staple diet of more than one-half of the global population. 10 Biotic stresses, such as rice blast, bacterial leaf steak, and rice sheath blight that are caused by Pyricularia oryae Cav., 11 Xanthomonas oryzae, 12 and Rhizoctonia solani, respectively, are making severe and devastating damage to rice production.…”

“…The crystal structure of the Fusarium oxysporum myosin I obtained with a resolution of 2.65 Å laid the foundation for designing novel myosin I inhibitors. − Our group discovered pyruvate kinase as a potent target of the lead compound YZK-C22 by drug-affinity-responsive target stability (DARTS) . Later, isothiazole-purines and triazolo-thiadiazoles were designed and synthesized as pyruvate kinase inhibitors with higher fungicidal activity than YZK-C22. , …”

3D-QSAR-Based Molecular Design to Discover Ultrahigh Active N-Phenylpyrazoles as Insecticide Candidates

“…Lead optimization can be successfully realized via adopting different strategies, such as the in silico tools, crystallographic approach, artificial intelligent approach, intermediate derivation approach, and so on. Target-based lead discovery is becoming more and more effective with the development of biological science and artificial intelligence . The three-dimensional quantitative structure–activity relationship (3D-QSAR) is widely used in the design of medicines and agrochemicals for rapidly predicting the potential of newly designed compounds. , …”

“…Target-based lead discovery is becoming more and more effective with the development of biological science and artificial intelligence. 10 The three-dimensional quantitative structure−activity relationship (3D-QSAR) is widely used in the design of medicines and agrochemicals for rapidly predicting the potential of newly designed compounds. 11,12 Lepidopteran pests such as Mythimna separata, Spodoptera frugiperda, and Plutella xylostella causing great damage to crop growth and production in the modern agricultural system are widely distributed over the world.…”