Asymmetric syntheses of ent -pimarane diterpenoids.

Aromatic ent -pimaranes are a group of aromatized tricyclic diterpenoids that exhibit diverse bioactivities. In this work, the first total syntheses of two aromatic ent -pimaranes were achieved via a C-ABC construction sequence enabled by chiral auxiliary controlled asymmetric radical polyene cyclization, and the subsequent substrate-controlled stereo-/regio-specific hydroboration of alkene allowed for access to both natural products with C19 oxidation modifications.