Asymmetric [3,3]-Sigmatropic Rearrangement of Sulfoniums for the Synthesis of Quaternary Center-Containing Polycyclic Molecules: Application to the Total Synthesis of Myrmenaphthol A

The asymmetric total synthesis of myrmenaphthol A, a natural product isolated from a Hawaiian sponge of the genus myrmekioderma, has been achieved in 12 steps. The key transformation of this synthesis is a gold-catalyzed [3,3]-sigmatropic rearrangement of sulfonium, starting from a chiral sulfoxide substrate and propargyl silane. The development of the methodology included the synthesis of benz[e]inden-2-one derivatives with quaternary centers (51-78% yield, 90-99% ee).