2-Propenoic acid, 3-(4,7-dihydro-6-hydroxy-4,7-dioxo-5-benzofuranyl)-, .delta.-lactone 483-36-3 4H-Furo[3,2-g][1]benzopyran-4,7,9-trione Bergaptenquinone NSC401268 Psoralen quinone