Diversity-Oriented Synthesis of Natural-Product-like Libraries Containing a 3-Methylbenzofuran Moiety for the Discovery of New Chemical Elicitors

A Novel AHAS-Inhibiting Herbicide Candidate for Controlling Leptochloa chinensis: A Devastating Weedy Grass in Rice Fields

Given the prevalence of the malignant weed Chinese Sprangletop (Leptochloa chinensis (L.) Nees) in rice fields, the development of novel herbicides against this weed has aroused wide interest. Here, we report a novel diphenyl ether-pyrimidine hybrid, DEP-5, serving as a systematic pre/postemergence herbicide candidate for broad-spectrum weed control in rice fields, specifically for L. chinensis. Notably, DEP-5 exhibits over 80% herbicidal activity against the resistant biotypes even at 37.5 g a.i./ha under greenhouse conditions and has complete control of L. chinensis at 150 g a.i./ha in the rice fields. We uncover that DEP-5 acts as a noncompetitive inhibitor of acetohydroxyacid synthase (AHAS) with an inhibition constant (Ki) of 39.4 μM. We propose that DEP-5 binds to AHAS in two hydrophobic-driven binding modes that differ from commercial AHAS inhibitors. Overall, these findings demonstrate that DEP-5 has great potential to be developed into a herbicide for L. chinensis control and inspire fresh concepts for novel AHAS-inhibiting herbicide design.

Scandium-Catalyzed Phenol-Directed Construction of 5-Carbonyl-4-hydroxybenzofurans via Intramolecular Friedel-Crafts Reaction

Herein we report a scandium-catalyzed regioselective synthesis of 5-carbonyl-4-hydroxybenzofurans via a phenol-directed intramolecular Friedel-Crafts reaction. This synthetic method was applied for the total synthesis of furanoflavones. Experimental studies and density functional theory calculations suggest that hydrogen bond interactions between the phenolic hydroxy group and the scandium complex realize regioselective intramolecular cyclization.

Design, step-economical diversity-oriented synthesis of an N-heterocyclic library containing a pyrimidine moiety: discovery of novel potential herbicidal agents

The synthesis of highly diverse libraries has become of paramount importance for obtaining novel leads for drug and agrochemical discovery. Herein, the step-economical diversity-oriented synthesis of a library of various pyrimidine-N-heterocycle hybrids was developed, in which a 4,6-dimethoxypyrimidine core was incorporated into nine kinds of N-heterocycles. A total of 34 structurally diverse compounds were synthesized via a two-step process from very simple and commercially available starting materials. Further, in vivo biological screening of this library identified 11 active compounds that exhibited good post-emergence herbicidal activity against D. sanguinalis at 750 g ai per ha. More importantly, pyrimidine-tetrahydrocarbazole hybrid 5q showed good to excellent herbicidal activity against five test weeds at the same dosage. Pyrimidine-tetrahydrocarbazole hybrids represent a novel class of herbicidal agents that may become promising lead compounds in the herbicidal discovery process.

4-Hydroxy-3-methylbenzofuran-2-carbohydrazones as novel LSD1 inhibitors

Histone lysine specific demethylase 1 (LSD1 or KDM1A) is a potential therapeutic target in oncology due to its overexpression in various human tumors. We report herein a new class of benzofuran acylhydrazones as potent LSD1 inhibitors. Among the 31 compounds prepared, 14 compounds exhibited excellent LSD1 inhibitory activity with IC₅₀ values ranging from 7.2 to 68.8 nM. In cellular assays, several compounds inhibited the proliferations of various cancer cell lines, including PC-3, MCG-803, U87 MG, PANC-1, HT-29 and MCF-7. This opens up the opportunity for further optimization and investigation of this class compounds for potential cancer treatment.

Enhanced transcriptome responses in herbivore-infested tea plants by the green leaf volatile (Z)-3-hexenol

Green leaf volatiles (GLVs) play a vital role in enhancing herbivore-associated defense responses, but the mechanism by which they precisely regulate such responses is not well understood. (Z)-3-Hexenol (z3HOL), an important component of GLVs, effectively activates the defense of tea plants (Camellia sinensis) against a tea geometrid (TG) Ectropis obliqua Prout. To elucidate the molecular mechanisms of defense activation by z3HOL, RNA-Sequencing was employed to investigate the effect of z3HOL on transcriptome responses to TG in tea plants. A total of 318 upregulated genes were identified, and expression of 10 unigenes was validated by quantitative real-time PCR. Among these 318 upregulated genes, 56 were defense-related, including 6 key enzyme genes in jasmonic acid, and ethylene biosynthesis, 24 signal transduction genes, and 12 insect-responsive transcription factors. Most of the defense-related genes are induced by JA, TG, or wounding treatments, suggesting that JA signaling plays a vital role in z3HOL-induced tea defense against TG.

A Disease Resistance Elicitor Laminarin Enhances Tea Defense against a Piercing Herbivore Empoasca (Matsumurasca) onukii Matsuda

The tea plant (Camellia sinensis) suffers heavily from a harmful piercing pest, the tea green leafhopper (TLH) Empoasca (Matsumurasca) onukii Matsuda. In the present study, we studied the effect of an efficient elicitor of plant disease resistance, the β-1,3-glucan laminarin, on the induced defense against TLH in tea plants. Defense responses elicited by laminarin in tea include the activation of mitogen-activated protein kinases and WRKY, the burst of H₂O₂, salicylic acid, and abscisic acid, and the accumulation of direct-defense chemicals (including chitinase, phenylalanine ammonia lyase, callose, polyphenol oxidase, and flavonol synthase), as well as the production of volatile compounds. The laminarin-treated tea plants reduced the performance of TLH and enhanced the attractiveness to the egg parasitoid wasp of TLH, Stethynium empoascae Subba Rao. In the field experiment, laminarin application effectively reduced the number of TLH by attracting parasitoids. These results suggest that laminarin can induce protection against TLH by regulating signaling pathways in tea plant. Our study also proposes an environment friendly strategy for the integrated management of an economically important piercing pest.

Recent Advances in Synthetic Chemical Inducers of Plant Immunity

Different from the conventional biocidal agrochemicals, synthetic chemical inducers of plant immunity activate, bolster, or prime plant defense machineries rather than directly acting on the pathogens. Advances in combinatorial synthesis and high-throughput screening methods have led to the discovery of various synthetic plant immune activators as well as priming agents. The availability of their structures and recent progress in the mechanistic understanding of plant immune responses have opened up the possibility of identifying new or more potent chemical inducers through rational design. In this review, we first summarize the chemical inducers identified through large-scale screening and then discuss the emerging trends in the identification and development of novel plant immune inducers including natural elicitor based chemical derivation, bifunctional combination, and computer-aided design.

Diversity-Oriented Synthesis of Natural-Product-like Libraries Containing a 3-Methylbenzofuran Moiety for the Discovery of New Chemical Elicitors

Natural products are a major source of biological molecules. The 3-methylfuran scaffold is found in a variety of plant secondary metabolite chemical elicitors that confer host-plant resistance against insect pests. Herein, the diversity-oriented synthesis of a natural-product-like library is reported, in which the 3-methylfuran core is fused in an angular attachment to six common natural product scaffolds-coumarin, chalcone, flavone, flavonol, isoflavone and isoquinolinone. The structural diversity of this library is assessed computationally using cheminformatic analysis. Phenotypic high-throughput screening of β-glucuronidase activity uncovers several hits. Further in vivo screening confirms that these hits can induce resistance in rice to nymphs of the brown planthopper Nilaparvata lugens. This work validates the combination of diversity-oriented synthesis and high-throughput screening of β-glucuronidase activity as a strategy for discovering new chemical elicitors.