Rapid Access to the “in,out”‐Tetracyclic Core of Ingenol

In …︁ out …︁ shake it all about! The tetracyclic core of ingenol has been prepared in a convergent synthesis. The pinacol-type rearrangement of an epoxy alcohol provides a simple, expedient solution to the challenging “inside–outside” intrabridgehead stereochemistry of ingenol (see scheme, TBS=tert-butyldimethylsilyl).