Ulosantoin, a phosphorylated hydantoin, has been isolated from organic soluble extracts of the sponge Ulosa ruetzeri and found to exhibit marked insecticidal activity against tobacco hornworm larvae and cockroaches. The structure was determined by X-ray diffraction ananlysis. A structurally related compound, dimethyl N2-creatininylphosphate , was also isolated from the sponge extract but was inactive in the insecticidal screens
