Antitumor agents. Part 212: Bucidarasins A–C, three new cytotoxic clerodane diterpenes from Bucida buceras

As part of a study on antitumor agents from rainforest plants, four new clerodane diterpenes, bucidarasins A–D (1–4), were isolated from Bucida buceras. Their structures were elucidated from detailed 2D NMR analyses. Compounds 1–3 showed potent cytotoxicity against human tumor cell lines with IC50 values of 0.5–1.9 μM. The potency was retained in drug resistant lines.