We describe an enantioselective synthetic route to the leucosceptroid family of natural products that allowed to synthesize several members of this natural product familiy.
The cotton bollworm (Helicoverpa armigera) and the beet armyworm (Spodoptera exigua) are among the most destructive agricultural pests in nature and they affect vegetables and other crops worldwide. Protection against them has been achieved by the use of sex-pheromone traps, insecticides, and transgenic crops. However, resistance to insecticides has developed over the last decade and new chemical agents are necessary to prevent further crop damage from these pests. Leucosceptrum canum Smith (“Bird’s Coca Cola tree”) and Colquhounia coccinea var. mollisa, plants found in China and Nepal, are remarkably resistant to herbivores and pathogens. Extraction and isolation of the trichomes, flowers, and whole leaves recently led to the discovery of novel antifeedant „leucosceptroid“ natural products. So far, no general and practical strategy which allows for the collective synthesis of the leucosceptroid family of natural products was available to the scientific community. Herein, we describe an enantioselective synthetic route to the leucosceptorids that allowed to synthesize several members of this natural product familiy. Additionally, we were able to partially mimic the biosynthetic pathway and the current findings support the hypothesis that two biosynthetic pathways are operative in the plant. The presented results should also serve as an example that, today, total synthesis is capable of providing practical access to a whole natural product family and deliver ample quantities of important intermediates as wells as the target compounds for further biological investigations. |