Phorbasterones A−D, Cytotoxic <i>Nor</i>-Ring A Steroids from the Sponge <i>Phorbas amaranthus</i>

Abstract

The sponge Phorbas amaranthus from Florida contains the new ring A-contracted steroids, phorbasterones A-D, and the known anthosterones A and B. The structures of phorbasterones A-D were determined by interpretation of their spectroscopic data. Phorbasterones show moderate cytotoxicity against HCT-116 tumor cells.