To identify fungicide lead compounds with novel scaffold and high efficacy, a library of 4,5-dihydrotetrazolo [1,5-a]thieno [2,3-e]pyridine derivatives, consisting of 10 newly synthesized compounds and 12 previously reported compounds, was evaluated for their potential as fungicide agents. In vitro bioassay results indicated that some target compounds exhibited certain antifungal activity against the tested fungi at a concentration of 50 μg/mL. Especially, compounds I-1, I-5, I-7, and I-12 demonstrated promising antifungal activity against C. arachidicola, R. solani, and S. sclerotiorum, with EC₅₀ values ranging from 4.61 to 6.66 μg/mL. Additionally, transcriptome analysis revealed that the molecular mode of action of compound I-12 involves the inhibition of nitrogen metabolism and the proteasome pathway. The present work demonstrates that 4,5,6,7-tetrahydrothieno [3,2-b] pyridine represents a promising lead scaffold and provides important theoretical foundations and innovative perspectives for the development of novel and highly efficient fungicides.

In continuation of our efforts to identify novel herbicide lead compounds with enhanced activity, a series of eighteen 5-acylbarbituric acid derivatives containing a pyrimidinedione moiety were designed and synthesized. Their herbicidal activities were subsequently evaluated in the greenhouse. Bioassay results demonstrated that most of the newly synthesized compounds exhibited significant herbicidal efficacy at a dosage of 150 g ha⁻¹, with compounds BA-I-2, BA-II-2, BA-III-2, and BA-III-5 achieving complete inhibition of the tested weeds. Further investigation into the herbicidal spectrum revealed that compounds BA-II-2 and BA-III-2 displayed excellent herbicidal activity against 14 and 13 out of 16 tested weed species, respectively, with inhibition rates exceeding 80% at dosages as low as 18.8 g ha⁻¹. More promisingly, compound BA-III-2 was found to be safe for Triticum aestivum at a dosage of 37.5 g ha⁻¹. Molecular mode of action studies, including phenotypic observations, membrane permeability evaluations, and molecular docking, suggested that BA-III-2 may function as a protoporphyrinogen IX oxidase (PPO) inhibitor. The present work indicates that BA-III-2 holds potential as a PPO-inhibiting herbicide for effective weed control in wheat fields and is expected to provide important theoretical foundations for the development of novel and highly efficient herbicides.

In continuation of our efforts to identify novel herbicide lead compounds, twenty new 5-(1-amino-4-phenoxybutylidene)barbituric acid derivatives containing an enamino diketone motif were synthesized and evaluated for their herbicidal activities. The greenhouse bioassay results indicated that several of the target compounds, including BA-1, BA-2, BA-5, BA-18, and BA-20, exhibited notable post-emergence herbicidal activity, with sum inhibition rates exceeding 70% at a dosage of 150 g ha⁻¹, which was superior to that of the commercial herbicide flumiclorac-pentyl (FP). The structure–activity relationship analysis demonstrated that the steric and electronic effects of the R group, as well as the lipophilicity of the target compounds, significantly influenced herbicidal activity. Among these, BA-1 was identified as a promising herbicide lead compound due to its high total herbicidal efficacy, broad-spectrum activity, and favorable crop safety profile. Molecular simulation studies indicated that BA-1 binds effectively to Nicotiana tabacum protoporphyrinogen IX oxidase (NtPPO), suggesting its potential as a novel PPO inhibitor. This study highlights BA-1 as a promising lead compound for the development of novel PPO-inhibiting herbicides.