Chamobtusin A, a Novel Skeleton Diterpenoid Alkaloid from Chamaecyparis obtusa cv. tetragon

The novel diterpenoid alkaloid chamobtusin A (1) was isolated from the branches and leaves of Chamaecyparis obtusa cv. tetragon. Its structure and relative stereochemistry were mainly determined by MS, 2D NMR, and X-ray methods. The methanol extracts, total alkaloids of C. obtusa cv. tetragon, and chamobtusin A were tested for their cytotoxicities against A549 and K562 human tumor cell lines.