Tasnemoxides A-C, new cytotoxic cyclic norsesterterpene peroxides from the Red Sea sponge Diacarnus erythraenus.

Tasnemoxides A-C (1-3), three new cytotoxic cyclic norsestertepene peroxides, were isolated from the Red Sea sponge Diacarnus erythraenus, together with the known compound sigmosceptrellin B (4). The structural determination of the isolated compounds was based on extensive 1D and 2D NMR studies and mass spectral determinations. Compounds 1-3 showed moderate cytotoxicity against three cancer cell lines.