Total Synthesis of Dactyloquinone A and Spiroetherone A via a Metal‐Hydride Hydrogen Atom Transfer (MHAT) Process and a Quinol–Enedione Rearrangement

Overview & Synopsis

We report the total synthesis of dactyloquinone A and spiroetherone A from a meroterpenoid scaffold obtained by the deconjugative alkylation of a Wieland–Miescher type ketone. For dactyloquinone A, we employed an intramolecular hydrofunctionalisation of the internal trisubstituted alkene with a quinone monoacetal via a metal‐hydride hydrogen atom transfer (MHAT) process to form the key C─O bond. For spiroetherone A, we relied on a stereospecific quinol–spiroenedione rearrangement. The initially postulated structure of spiroetherone A was first synthesized, but was found to be different from the natural product. Finally, spiroetherone A was shown to be epimeric at the spirocyclic carbon. This finding was confirmed by total synthesis involving epimerization of the spirocycle via a late‐stage singlet oxygen [4+2] cycloaddition to a cyclohexadiene derived from the initial enedione.