Rigidone, a sesquiterpene o-quinone from the gorgonian Pseudopterogorgia rigida

As part of a search for novel biologically active compounds in the Macrophage Scavenger Receptor (MSR) assay, the EtOAc extract of a gorgonian coral, Pseudopterogorgia rigida, was shown to be active. Bioassay-guided fractionation of the extract yielded curcuphenol, curcuhydroquinone, curcuquinone, and a novel o-quinone, rigidone (1). The structure and stereochemistry of 1 was determined by interpretation of spectral data and chemical transformation.