New quinones from a dictyoceratid sponge

Five new quinones have been isolated from a sponge tentatively classified as Stelospongia conulata. Isospongiaquinone (7) has a rearranged drimane skeleton whereas spongiaquinone (19), cyclo- spongiaquinone-1 (20), cyclospongiaquinone-2 (21) and dehydrocyclospongiaquinone-1 (22) have a normal drimane skeleton. The structures of these were derived from chemical and spectral evidence.