Ternifolide A, a New Diterpenoid Possessing a Rare Macrolide Motif from Isodon ternifolius

Ternifolide A (1), a new diterpenoid featuring a unique 10-membered lactone ring formed between C-6 and C-15, along with ternifolide B (2), a nor-diterpenoid, and ternifolide C (3) were isolated from the leaves of Isodon ternifolius. Both H-8 and H-9 being α-orientations in compound 1 were found for the first time. The absolute configurations of 1 and 3 were confirmed by X-ray diffraction study. Compounds 1 and 3 were evaluated for their cytotoxicity.