The structures and stereochemistry of cytotoxic sesquiterpene quinones from dactylospongia elegans

The cytotoxicity of a crude extract from Dactylospongia elegans stimulated a search for the active constituents. The structures and absolute stereochemistry are elucidated for four new 9, 11,18, 19, and thirteen previously described compounds, 3, 4, 6a, 7, 8, 10, 12 - 17, 21. These compounds were isolated from collections of D. elegans obtained from three different Indo-Pacific regions, Fiji, Papua New Guinea, and Thailand. This species appears to elaborate a broader range of the mixed biogenesis sesquiterpene-hydroquinone (-quinone) metabolites in comparison to those of other sponges or seaweeds. Three compounds, 4, 9, and 13, were potent (IC₅₀'s were less than 1 μg/mL). The quinone ring appears to be essential for this in vitro activity.