156.Synthetic Strategy for Construction of Highly Congested Tetracyclic Core (6–5–7–4) of Harziane Diterpenoids

Qian Tu, Zheyuan Wang, Zhongchao Zhang, Jun Huang*, and Zhen Yang*

Org. Lett. 2021, 23(11), 4088–4093

The structurally intriguing tetracyclic core of complex harziane diterpenoid was constructed in 14 steps from commercially available 3-ethoxycyclohex-2-en-1-one. The key steps were a Mn/Cu-mediated oxidative 1,3-dicarbonyl radical cascade cyclization reaction, which diastereoselectively formed the core of dimethylbicyclo[3.2.1]octane structure, and a Au-catalyzed diastereoselective formal [2 + 2] cycloaddition for construction of the harziane diterpenoid tetracyclic framework. The developed method paves the way for achieving total synthesis of this type of complex natural product.