Tricalysiolide G, and Tricalysiols A and B : rearranged ent-Kaurane-Type and ent-Kaurane-Type Diterpenoids from the Leaves of Tricalysia dubia (Lindl.) Ohwi

Three rearranged ent-kaurane diterpenes having the cafestol-type framework were isolated from the leaves of Tricalysia dubia. Two of them were found to be known diterpenoids, tricalysiolides B and C. Tricalysiolide B was isolated as colorless prisms in this experiment and its three dimensional structure was determined by X-ray crystallography. The remaining one was a new compound and named tricalysiolide G. Two new ent-kaurane-type diterpenoids, to which tricalysiols A and B were given as trivial names, were also isolated. The structures of the new compounds were elucidated from spectroscopic evidence.