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 obtaine d. The structures of compounds were established by both spectroscopic and c rystallographic 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 b eetle (Tribolium confusum Duv.). The results of the tests proved that two c ompounds, (1R,4R,6R)-(-)-4-( 1-methylethenyl)-9-oxabicyclo[4.3.0]nonan-8-on e (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 Suit.). The activity depends on the absolute c onfigurations of compound chiral centers. Additionally, the lactones 8a and 8b are characterized by interesting fragrances.