Synthesis of bioactive sesterterpenolides from ent-halimic acid. 15-epi-ent-Cladocoran A and B.

The bioactive sesterterpenoid γ-hydroxybutenolides 15,18-bisepi-ent-Cladocoran A and B, 1 and 2, and 15-epi-ent-Cladocoran A and B, 57 and 55, were synthesized from ent-halimic acid. The synthesized sesterterpenolids 2, 55, 57, and 59 inhibited cellular proliferation (IC50 ≅ 2 μM) of a number of human leukaemic and solid tumor cell lines.