Synthesis of Atisine, Ajaconine, Denudatine, and Hetidine Diterpenoid Alkaloids by a Bioinspired Approach

A unified approach to four different (atisine, ajaconine, denudatine, and hetidine) diterpenoid alkaloid skeletons was developed and applied to the total synthesis of the natural products dihydroajaconine (2, atisine type) and gymnandine (4, denudatine type). The synthesis features a biogenetically inspired strategy that relies on C−H oxidation, aza‐pinacol coupling, and aza‐Prins cyclization as key steps. Worthy cores: A unified synthetic approach to four types of diterpenoid alkaloids with cagelike structures was developed on the basis of biogenetically inspired C−H oxidation, aza‐pinacol coupling, and aza‐Prins cyclization reactions (see scheme). Compounds synthesized with the four target core structures included the natural products dihydroajaconine and gymnandine.