Consecutive sigmatropic rearrangements in the enantioselective total synthesis of (−)-joubertinamine and (−)-mesembrine

Joubertinamine and mesembrine are two related alkaloids isolated from Sceletium plants. From the perspective of chemical synthesis, the major challenge posed by joubertinamine and mesembrine is undoubtedly the construction of the benzylic quaternary stereogenic center. We became intrigued by the prospect of applying successive sigmatropic rearrangements to build the key structural features of these alkaloids in enantioselective manner. In this article, we detail our results in this area, which include the enantioselective total synthesis of (−)-joubertinamine and (−)-mesembrine.