Two New Degraded Triterpenoids and a Novel seco-Norabietane Diterpene from the Root Bark of Azadirachta indica

摘要

Three new compounds, the degraded ring C-seco-tetranortriterpenoid nimbolicidin (1), the degraded hexanortriterpenoid nimbocin (2), and the seco-norabietane diterpene nimbocinin (3), were isolated from the root bark of Azadirachta indica A.JUSS. Compound 1 is O-bearing both at C(28) and C(29), which has been hitherto unreported in tetranortriterpenoids; 2 represents the first hexanortriterpenoid with a truncated apotirucallane (or apoeuphane) skeleton; 3 is an unprecedented seconorabietane. Spectroscopic data and chemical transformations of these compounds provided their complete structures.