Microphyllandiolide, a New Diterpene with an Unprecedented Skeleton from Salvia microphylla

Microphyllandiolide (1), an unprecedented rearranged clerodane-type diterpene with a 9/3 bicyclic ring system, was isolated from the aerial parts of Salvia microphylla Kunth. Its structure was elucidated by analysis of its spectroscopic data and confirmed by single crystal X-ray diffraction analysis. A possible biogenesis for microphyllandiolide (1) is proposed.