The bioactive sesterterpenoid gamma-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 (IC(50) congruent with 2 micro M) of a number of human leukaemic and solid tumor cell lines.

Two new diterpenic acids with an ent-halimane skeleton have been isolated from the aerial parts of Halimium viscosum (Villarino de los Aires chemotype) and separated as methyl esters. These diterpenes were 13-oxo-14, 15-dinor-1(10),11E-ent-halimadien-18-oic acid and 15-hydroxy-1(10),13Z-ent-halimadien-18-oic acid.