2-Propenoic acid, 3,3'-(4,6-dihydroxy-1,3-phenylene)bis-, di-.delta.-lactone 2H,8H-Benzo[1,2-b:5,4-b']dipyran-2,8-dione 4413-05-2 Coumarino[7,6-.alpha.]pyrone Coumarylpyrone NSC244431 cis-Benzodipyrone