Diterpenoids from Isodon adenantha

Eleven new diterpenoids, adenanthins B-L (1-11), together with five known analogues, calcicolin B (12), adenanthin (13), weisiensin A (14), nervosanin (15), and forrestin C (16), were isolated from the aerial parts of Isodon adenantha The structures of 1-11 were elucidated on the basis of spectral methods, as well as the X ray crystallographic analysis of 11 Compounds 2, 5, and 14 showed significant inhibitory activities against K562 cells, with IC50 values less than 4 mug/mL, respectively.