Ring functionalization: The totalsynthesis of a naturalderivative of (−)‐13‐oxyingenol, a potent anti‐HIV diterpenoid, is reported. The key steps in this synthesis include a ring‐closing olefin metathesis and a Mislow–Evans‐type [2,3]‐sigmatropic rearrangement. This synthesis provides access to (−)‐13‐oxyingenol and itsnaturalderivative in 21 steps from a synthetic intermediate previously prepared