Euphomilones A and B, ent-Rosane Diterpenoids with 7/5/6 and 5/7/6 Skeletons from Euphorbia milii

Three highly modified ent-rosane diterpenoids, euphomilones A (1) and B (2) and euphomianol A (3), were isolated from the aerial parts of Euphorbia milii. The structures were elucidated from physical, spectroscopic, and X-ray diffraction data, as well as experimental and calculated electronic circular dichroism (ECD) analysis. Plausible biogenetic pathways to 1–3 are proposed. Also, compound 1 exhibited inhibition of receptor activator of nuclear factor-kappaB ligand (RANKL)-induced osteoclast formation (IC50 = 12.6 μM).