New Strategy in Agarofuran synthesis : Stereoselective construction of the tetrahydrofuran ring.

The role of plant secondary metabolites in host plant recognition, especially in oligophagous insects, is of great importance. Substances eliciting feeding responses of the insects have been extensively studied and numerous attempts have also been made in the past decades to isolate antifeedants from plants avoided by insect species. As the most studied of these plant secondary metabolites with antifeedant activity, but also in some cases insecticide activity, one should cite polygodial 1 1, waburganal 2 2, azadirachtine3 , toosendanine 4 4, clerodanes 5 (clerodine 5) and ecdysteroids 6 (20-hydroxyecdysone 6). However, the diversity of structure of these products, the diversity of their biological activities and their structural complexity did not allow establishment of unambiguous structure-antifeedant activity relationships.