Synthesis of β-aryl-γ-lactones and relationship: Structure – antifeedant and antifungal activity

Abstract

Eighteen racemic β-aryl-γ-lactones derived from simple aromatic aldehydes have been obtained in the chemical synthesis. Iodolactones (5c and 6c) were synthesized from (E)-4-(benzo[d][1′,3′]-dioxol-5′-yl)-but-3-en-2-one (1). Reductive dehalogenation of iodolactones 5a–c and 6a–c afforded γ-ethyl-γ-lactones (7a–c, 8a–c) whereas the unsaturated lactones (9a–c, 10a–c) were obtained by dehydrohalogenation of iodolactones. All synthesized lactones were fully characterized by spectroscopic data (NMR, IR, HRMS) and subjected to the tests on the antifeedant activity towards Tribolium confusum, Trogoderma granarium and Sitophilus granaries as well to the tests on the antifungal activity towards four Fusarium species. The biological tests allowed to find some relationships between the structure and biological activity of the compounds studied. γ-Ethyl- γ-lactones 7a–c, 8a–c and unsaturated lactones 9a–c, 10a-c were usually stronger antifeedants than their parent iodolactones 5a–c and 6a–c. trans-Iodolactones 6a–c were more active than cis isomers 5a-c both in antifeedant and antifungal assays. The structure of aromatic substituent was the key factor in antifungal activity. The lactones with benzo [d][1,3]dioxole ring (5c, 6c, 7c, 8c, 9c) were the most active whereas those with unsubstituted benzene ring exhibited almost no activity. Eighteen racemic β-aryl-γ-lactones have been synthesized and subjected to the tests on the antifeedant towards storage pests and antifungal activity towards some Fusarium species. γ-Ethyl-γ-lactones and unsaturated lactones were usually stronger antifeedants than their parent iodolactones. The lactones with benzo [d][1,3]dioxole ring exhibited the highest activity.