An Expedient Synthesis of a Functionalized Core Structure of Bielschowskysin

Photons in action: Cascade sequences, brevity, and efficiency are the hallmarks of the synthesis of a functionalized tricyclo[9.3.0.0]tetradecane ring system of the marine natural product bielschowskysin. The synthesis is achieved in five steps, with the key step being an exquisite intramolecular [2+2] photocycloaddition of a macrocyclic precursor (see scheme).