Obtusinones D and E, Linear and Angular Fused Dimeric Icetexane Diterpenoids from Premna Obtusifolia Roots

Two new dimeric icetexane diterpenoids, obtusinones D and E (1 and 2), were isolated from the root extracts of Premna obtusifolia. Obtusinone D (1) represents the first example of a novel linear fused dimeric icetexane, whereas obtusinone E (2) is an angular fused icetexane. The structures of 1 and 2 were elucidated on the basis of 1D and 2D NMR spectral data analysis.