Asymmetric Total Synthesis of Arcutinidine and Arcutinine

We have accomplished the asymmetric total synthesis of arcutinidine and arcutinine, two arcutine-type C20-diterpenoid alkaloids. A pentacyclic intermediate was rapidly assembled by using two Diels−Alder reactions. A cascade sequence of Prins cyclization and Wagner−Meerwein rearrangement was then developed to construct the core of arcutinidine, which was further elaborated into an oxygenated pentacycle through a scalable route. Chemoselective reductive amination followed by spontaneous imine formation furnished the pyrroline motif at a final stage.