Cytotoxic polyprenylated benzoylphloroglucinol derivatives with an unusual adamantyl skeleton from Hypericum sampsonii (Guttiferae).

[formula: see text] The structures of sampsoniones I and J, isolated from the aerial parts of the Chinese medicinal plant Hypericum sampsonii, have been elucidated by detailed spectral analysis. They are complex adamantyl derivatives, and sampsonione I is the first polyprenylated benzoylphloroglucinol derivative with the unique caged tetracyclo[7.3.1.1.0]tetradecane-2,12,14-trione skeleton. Cytotoxic sampsonione I has also been obtained by the biomimetic transformation of sampsonione J.