First synthesis of 3,16,20-polyoxygenated cholestanes, new cytotoxic steroids from the gorgonian Leptogorgia sarmentosa

Using tigogenin as starting material, (20S)-20-hydroxycholestane-3,6-dione (1), (16S, 20S)-16,20-dihydroxycholestan-3-one (2), (20S)-20-hydroxycholest-1-ene-3,16-dione (3) and (20S)-20-hydroxycholest-4-ene-3,16-dione (4), natural polyoxygenated steroids from the gorgonian, Leptogorgia sarmentosa, were synthesized in four steps. Antitumor activity against three tumor cell lines (breast cancer, MCF7, lung cancer NCI and oral cancer KB) was evaluated. Two compounds (3 and 4) showed strong activity against NCI (IC50 6.16 and 10.51 μM) and moderate activity against MCF7 and KB, the IC50 being in the range 30.65–47.22 μM. Compound 2 showed moderate activity against NCI (IC50 42.68 μM) but was inactive against MCF7 and KB whereas compound 1 showed no activity against all tested cells.