Design, Synthesis, and Herbicidal Activity of Naphthalimide-Aroyl Hybrids as Potent Transketolase Inhibitors

Design, Synthesis, and Herbicidal Activity Study of Novel Pyrazole-Carboxamides as Potential Transketolase Inhibitors

Transketolase (TKL; EC 2.2.1.1) has been identified as a potential new herbicide target. In order to discover highly herbicidal active compounds targeting TKL and improve their structural diversity for lead compounds, a series of pyrazole-carboxamides 7a-7v were designed and synthesized through structural optimization for pyrazole-containing phenoxy amide compound 4u. Among the synthesized compounds, compound 7r possessed excellent herbicidal efficacy against Digitaria sanguinalis (Ds) and Amaranthus retroflexus (Ar) by the small cup method (the inhibition about 95%, 100 mg/L) and the foliar spray method (the inhibition over 90%, 150 g ai/ha) in a greenhouse, which were superior to that of the positive control nicosulfuron. More significantly, compound 7r displayed good crop selectivity toward both maize and wheat even at 375 g of ai/ha. The studies on mode of action (MOA) of high herbicidal active compounds, including the enzyme inhibition activity, fluorescent quenching experiments, and molecular docking analysis between Setaria viridis (Sv)TKL and ligand, suggested that compound 7r acts as a typical TKL inhibitor, and the benzothiazole ring is an important motif for SvTKL inhibition activity. Above all, compound 7r could be a potential candidate for the development of herbicides with new MOA for weed control in maize and wheat field.

Design, Synthesis, and Herbicidal Activities of N-(5-(3,5-Methoxyphenyl)-(thiazole-2-yl))phenoxyacetamide Derivatives

Thiazole and phenoxyacetic acid are key moieties in many natural and synthetic biologically active agents. A series of N-(5-(3,5-methoxyphenyl)-(thiazole-2-yl))phenoxyacetamide derivatives 6an-6bd were designed and synthesized, and their structures were confirmed by NMR and HRMS. Most of derivatives exhibited superior inhibition of Echinochloa crusgalli (E.c.) and Lactuca sativa (L.s.) seed germination by the Petri dish bioassay. Indeed, herbicidal bioassays indicated that 6an (2-(2,4-dichlorophenoxy)-N-(5-(3,5-dimethoxyphenyl)-1,3,4-thiadiazol-2-yl)acetamide) had the best inhibition against L.s. (IC50 = 42.7 g/ha, 375 g/ha at field experiments). 6an also had no harmful effect on Zea mays at 2- to 4-fold field usage. Moreover, transcriptomics and metabolomics analysis showed that 6an significantly influenced cell metabolism, including galactose metabolism and ascorbate and aldarate metabolism. These discoveries highlight that 6an shows promise to be developed as a potential herbicide.

Design, Synthesis, and Herbicidal Activity of Pyrazole Amide Derivatives as Potential Transketolase Inhibitors

The design and synthesis of new herbicidal active compounds based on a new target are of great significance for the development of new herbicides. Transketolase (TK) plays a key role in the Calvin cycle of plant photosynthesis and has been confirmed as a potential candidate target to develop and discover new herbicides. To obtain compounds with ultraefficient targeting of TK, a series of pyrazole amide derivatives were designed and synthesized through structural optimization for lead compound 4u based on TK as the new target. The bioassay results showed that compounds 6ba and 6bj displayed a highly inhibitory effect with the root inhibition of about 90% against Digitaria sanguinalis (DS) and 80% against Amaranthus retroflexus (AR) and Setaria viridis (SV) by the small cup method, which was better than the positive control mesotrione and nicosulfuron. Furthermore, compounds 6ba and 6bj exhibited an excellent inhibitory effect with the inhibition of about 80% (against DS) and over 80% (against SV) at the dosage of 150 g of active ingredient/ha by the foliar spray method. The TK enzyme activity inhibition test showed that the inhibition effect of target compounds against TK was consistent with the results of herbicidal activities. Also, molecular docking analysis showed that compounds 6ba and 6bj went deep into the active cavity of TK, bound to TK by a strong interaction, and might act on the enzyme TK. Above of all, compounds 6ba and 6bj are promising herbicide lead compounds targeting TK. Hence, they could be developed into more efficient herbicides by further structural optimization.

Investigations into Simplified Analogues of the Herbicidal Natural Product (+)-Cornexistin

We report the design, synthesis and biological evaluation of simplified analogues of the herbicidal natural product (+)-cornexistin. Guided by an X-Ray co-crystal structure of cornexistin bound to transketolase from Zea mays, we attempted to identify the key interactions that are necessary for cornexistin to maintain its herbicidal profile. This resulted in the preparation of three novel analogues investigating the importance of substituents that are located on the nine-membered ring of cornexistin. One analogue maintained a good level of biological activity and could provide researchers insights in how to further optimize the structure of cornexistin for commercialization in the future.

Discovery of Bis-5-cyclopropylisoxazole-4-carboxamides as Novel Potential 4-Hydroxyphenylpyruvate Dioxygenase Inhibitors

4-Hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27; HPPD) represents a potential target for novel herbicide development. To discover the more promising HPPD inhibitor, we designed and synthesized a series of bis-5-cyclopropylisoxazole-4-carboxamides with different linkers using a multitarget pesticide design strategy. Among them, compounds b9 and b10 displayed excellent herbicidal activities versus Digitaria sanguinalis (DS) and Amaranthus retroflexus (AR) with the inhibition of about 90% at the concentration of 100 mg/L in vitro, which was better than that of isoxaflutole (IFT). Furthermore, compounds b9 and b10 displayed the best inhibitory effect versus DS and AR with the inhibition of about 90 and 85% at 90 g (ai)/ha in the greenhouse, respectively. The structure-activity relationship study showed that the flexible linker (6 carbon atoms) is responsible for increasing their herbicidal activity. The molecular docking analyses showed that compounds b9 and b10 could more closely bind to the active site of HPPD and thus exhibited a better inhibitory effect. Altogether, these results indicated that compounds b9 and b10 could be used as potential herbicide candidates targeting HPPD.

Transcriptomic Profiling of Fusarium pseudograminearum in Response to Carbendazim, Pyraclostrobin, Tebuconazole, and Phenamacril

Fusarium pseudograminearum has been identified as a significant pathogen. It causes Fusarium crown rot (FCR), which occurs in several major wheat-producing areas in China. Chemical control is the primary measure with which to control this disease. In this study, transcriptome sequencing (RNA-Seq) was used to determine the different mechanisms of action of four frequently used fungicides including carbendazim, pyraclostrobin, tebuconazole, and phenamacril on F. pseudograminearum. In brief, 381, 1896, 842, and 814 differentially expressed genes (DEGs) were identified under the carbendazim, pyraclostrobin, tebuconazole, and phenamacril treatments, respectively. After the joint analysis, 67 common DEGs were obtained, and further functional analysis showed that the ABC transported pathway was significantly enriched. Moreover, FPSE_04130 (FER6) and FPSE_11895 (MDR1), two important ABC multidrug transporter genes whose expression levels simultaneously increased, were mined under the different treatments, which unambiguously demonstrated the common effects. In addition, Mfuzz clustering analysis and WGCNA analysis revealed that the core DEGs are involved in several critical pathways in each of the four treatment groups. Taken together, these genes may play a crucial function in the mechanisms of F. pseudograminearum's response to the fungicides stress.