Perylenequinone Natural Products: Evolution of the Total Synthesis of Cercosporin

Abstract
The evolution of the first total synthesis of perylenequinone cercosporin is described. The key features developed during these efforts include a biscuprate epoxide alkylation, installation of the methylidene acetal, palladium-catalyzed O-arylation, and C3,C3′-decarbonylation. Due to the rapid atropisomerization of the helical axis of cercosporin (at 37 °C), the sequencing of these transformations was critical. To this end, the developed protocol enabled the formation of a key advanced intermediate on preparative scale absent any atropisomerization. Furthermore, the O-arylation proved to be general, and the strategy was used in an improved synthesis of a helical chiral perylenequinone structure.