Synthetic Studies Toward Ent-Kaurene Natural Products: An Application of Carbon–Carbon Bond Activation in Synthesis

Recent work in the area of transition metal catalyzed carbon–carbon (C–C) σ-bond activation has allowed for new strategic bond disconnection. Toward this end, the Dong lab has developed a Rh(I)-catalyzed C–C bond activation/olefin insertion strategy to access highly polycyclic scaffolds found in natural products. Of specific interest are the ent-kaurenes eriocalyxin B and isodonal. Herein, we disclose our synthetic efforts toward the family through a C–C activation method. Other key steps in the synthesis include a tandem Birch reduction propargylation reaction as well as a carbon–oxygen bond cleavage / lactonization sequence.