Synthesis and antifungal activity of cyclic quaternary ammonium salts of N-hydronopyl Tetrahydropyrrole compounds

<bold>Objective</bold> This study aims to synthesize cyclic quaternary ammonium salts from β-pinene of turpentine origin and develop broad-spectrum，low-resistance botanical antimicrobials for the green management of plant diseases. <bold>Method</bold> N-hydronopyl tetrahydropyrrole was first prepared from hydronopyl chloride and tetrahydropyrrole，then quaternised with α-bromoacetophenones or benzyl bromides to furnish the corresponding cyclic quaternary ammonium salts.The structures were confirmed by IR and NMR spectroscopy.The inhibitory activities of eight plant pathogenic fungi were tested by mycelial growth rate method，and the inhibitory mechanisms of some compounds against specific plant pathogenic fungi were preliminarily explored. <bold>Result</bold> Twelve cyclic quaternary ammonium salts were synthesized in ≥85% yield.At 100 mg/L，The inhibitory rates of compounds 3b，3c，3d，5a and 5b against <italic>Rhizoctonia solani</italic>，<italic>Sphaeropsis sapinea</italic>，<italic>Phytophthora parasitica var.nicotianae</italic>，<italic>Poria vaporaria</italic> and <italic>Poria vaporaria</italic> reached or approached 100%.Moreover，compounds 3b，3c，3d and 5b also showed significant activity against <italic>Colletotrichum fructicola</italic>，<italic>Fusarium verticillioides</italic> and <italic>Coriolus versicolor</italic>.Compounds 3b and 3d were selected for mechanism research on the pathogen causing <italic>Fusarium oxysporum</italic> f. sp. <italic>niveum</italic>.The results indicated that both compounds killed the fungus by inhibiting mycelial growth，altering morphology and increasing membrane permeability. <bold>Conclusion</bold> Among the 12 synthesized hydronopyl cyclic quaternary ammonium salts，the compounds with Br or Cl atoms at the para or meta positions on the benzene ring exhibit better activity.It provides new experimental basis for the chemical processing and utilization of β-pinene and the in-depth study of the structure-activity relationship of pinene derivatives.