Lactones. 9. Synthesis of terpenoid lactones-active insect antifeedants

Starting from (+)- and (-)-perillyl alcohols, via Claisen rearrangement and iodolactonization, four enantiomeric pairs of gamma-lactones were obtained. The structures of compounds were established by both spectroscopic and crystallographic methods. The lactones were tested for antifeeding activity toward grain storage pests-the granary weevil beetle (Sitophilus granarius L.), the khapra beetle (Trogoderma granarium Ev.), and the confused flour beetle (Tribolium confusum Duv.). The results of the tests proved that two compounds, (1R,4R, 6R)-(-)-4-(1-methylethenyl)-9-oxabicyclo[4.3.0]nonan-8-one (8a) and its enantiomer (8b), are very active antifeedants against all of the above tested species. The lactone 8b is also active against the peach-potato aphid (Myzus persicae Sulz.). The activity depends on the absolute configurations of compound chiral centers. Additionally, the lactones 8a and 8b are characterized by interesting fragrances.