Koilodenoids A–G, immunosuppressive spiro dimers of diterpenoids from Koilodepas hainanense: structural elucidation and biomimetic transformation

Seven new and immunosuppressive dimeric diterpenoids were elucidated. Compound 1 possesses a new carbon skeleton. The biomimetic transformation of 2 into 1 was achieved under mild, as well as peroxide- and metal-free conditions.