Michael Addition for the Synthesis of Octahydroindole Natural Products

Significance

Pansare and co-workers report an enantioselective route toward the aryloctahydro­indole core of several natural products. Their approach is based on the highly enantio- and dia­stereoselective Michael addition between ketones 1 and nitroalkenes 2 using the triamine salt catalyst 3. The resulting γ-nitro ketone 4a was diastereoselectively transformed into the cis-octahydro-indole 7 in five steps. This intermediate was further functionalized to tetracycle 8, thus completing a formal synthesis of (-)-pancracine.