Résumé : Sphaeropsidins A (1), B (7) and C (10), three fungal phytotoxins, unrearranged pimarane diterpenes produced by Diplodia cupressi and 10 semisynthetic derivatives were evaluated for their in vitro anticancer activities. Among these 13 compounds, sphaeropsidin A and two derivatives (2 and 6) thereof display 50% growth-inhibitory concentration in the low micromolar range for all cell lines analyzed. Structure activity relationship paralleled the phytopathogenic and antimicrobial ones except regarding the vinyl group at C-13 that does not seems to be required as it is for their antipathogenic activity. © 2012 Phytochemical Society of Europe.