Abstract: During the course of our studies on the biologically active consti-tuents of Rabdosia plants, we examined the etrereal extract of the leaves of Rabdosia bulleyana (Diels) Hara collected in the Cangshan Mountain, Yunnan, China. A new diterpenoid having a ent-Kaurene-skeleton, bulleyanin, was isolated. Its yield is 0.4% of the leaves and it shows tumor-inhibitor activities for S-180, ECA, and etc. of mice. The structure of the new compound was elucidated by spectroscopic and chemical evidences as follows; bulleyanin, mp 240-244℃, C28H38O10, ent-12β-hydroxy-1α, 3α, 7β, 14α-tetraacetoxy-16- Kauren-15-one (I ). 1H NMR data of bulleyanin and its derivatives, 13C NMR data of bulleyanin and dehydrobulleyanin have been assigned. 13C NMR assignments are based on a combination of proton noise decoupling, off-resonance decoupling and com-parison with related compounds.

Key words: Rabdosia bulleyana