Total Synthesis of the Tetracyclic Sesquiterpene (±)‐Punctaporonin C

Tailor made for the target molecule 2, the carbon skeleton of the epoxide 1 was integrated entirely into the natural product. A regioselective intramolecular [2+2] photocycloaddition and subsequent Wacker oxidation enabled the specific and successive incorporation of the two terminal double bonds of 1 into the unusual oxatetracyclo[6.3.2.01,4.05,13]tridecane skeleton of 2, which was synthesized in 24 steps and 2.0 % overall yield. TBDMS=tert-butyldimethylsilyl.