Total Synthesis of Dactyloquinone A and Spiroetherone A.

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 hydrofunction-alisation 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, spi-roetherone A was shown to be epimeric at the spirocyclic carbon. This finding was confirmed by total synthesis involving epimeri-zation of the spirocycle via a late-stage singlet oxygen [4+2] cycloaddition to a cyclohexadiene derived from the initial ene-dione.