Total Syntheses of Scaparvins B, C, and D Enabled by a Key C-H Functionalization.

The clerodane diterpene family possesses an impressive range of bioactivities and high synthetic challenge due to their unique amalgamation of rings, stereocenters, and oxygenation. Herein, we disclose the first total syntheses of three members, scaparvins B, C, and D, through a route fueled by several chemoselective and carefully orchestrated steps. One such operation is a tailored late-stage C-H functionalization converting a carboxylic acid into a lactone through the oxidation of a tertiary C-H bond under conditions that minimize epoxidation of an alkene. This step, among others, afforded critical functionality to complete the targets. In addition, use of an appropriate chiral catalyst with a Rawal diene renders the sequence enantioselective.