Stereocontrolled Construction of the Tricyclic Framework of Tiglianes and Daphnanes by an Oxidative Dearomatization Approach

An appropriately functionalized [5–7–6] tricyclic framework of tigliane and daphnane diterpenes containing seven contiguous stereocenters has been prepared in 10 steps from very simple building blocks in a modular and stereocontrolled fashion. The key features of this approach involve an efficient visible light-induced singlet oxygen oxidative dearomatization and an array of substrate-controlled highly diastereoselective transformations. This work provides a model strategy for rapid and diverted synthesis of natural and unnatural molecules sharing the common skeleton.