Collective total synthesis of fusicoccane diterpenoids via Yu 5+2+1 cycloaddition and oxidative Nazarov cyclization

The fusicoccane diterpenoids have triggered particular interest from the organic synthesis community in recent years, owing to their promising biological profiles and complex chemical structures. Here, we report collective, asymmetric total syntheses of five fusicoccane diterpenoids, namely fusicoauritone, fusicogigantones A and B, fusicogigantepoxide, and anadensin. This work features a Yu 5+2+1 cycloaddition that is shown to be a swift approach to access the 5,8-bicyclic ring system and an oxidative Nazarov cyclization that facilely fabricated the critical cyclopentenone moiety via an unfunctionalized tertiary divinyl carbinol (TDC) substrate. The substrate scope study of the oxidative Nazarov cyclization also revealed a general and robust transformation that is capable of synthesizing highly substituted cyclopentenones via unfunctionalized TDCs.