The novel skeleton compounds, chamaecypanone C (3) and obtunorlignan A (4) were isolated from the heartwood of Chamaecyparis obtusa var. formosana. The structure of 3 was elucidated as a dimeric of monoterpene and norlignan with tricyclo- [5.2.2.0(2.6)]undecane and the structure of 4 was elucidated as a norlignan skeleton by spectroscopic methods. Compound 3 exhibits potent cytotoxic activity against several human cancer cells with IC50 values ranging from 0.19 to 0.52 mu M, whereas 4 has no activity. (c) 2007 Published by Elsevier Ltd.
