Total synthesis of bioactive tetracyclic norditerpene dilactones

Tetracyclic norditerpene dilactones are an important class of terpenoids that have been isolated from both terrestrial and marine sources, typically from Podocarpus plants and from filamentous fungi. This class of molecules shares a common 6/6/6/5 tetracyclic ring skeleton, which possesses a densely oxygenated carbon framework and contiguous stereocenters. What's more challenging for synthetic chemists are the consecutive sp²-hybridized carbon centers, which exacerbates the strain/rigidity of the whole molecule. In addition, many of these molecules display promising biological activities, such as antitumor, insecticidal, anti-feedant, allelopathic, and antibiotic activities. The unique structures and interesting biological profiles of norditerpene dilactones have attracted considerable attention from synthetic chemists. Herein we summarize the synthetic efforts with respect to tetranorditerpene dilactones.