Diterpenoid constituents of Rabdosia umbrosa (MAXIM.) HARA: Isolation and structure elucidation of two new diterpenoids, umbrosianin and rabdoumbrosanin.

Diterpenoid constituents of the aerial parts of Rabdosia umbrosa (MAXIM.) HARA, collected in Gotenba City and Shizuoka City were separately examined. A new compound, umbrosianin (1), has been isolated together with two known compounds, umbrosin A (2) and kamebanin (3), from the former and a new compound, rabdoumbrosanin (6) has been isolated together with four known compounds, shikoccidin (4), isodomedin (5), shikoccin (7) and rabdolatifolin (8), from the latter. The structures of the new compounds have been elucidated on the basis of spectral and chemical evidence.