3',6'-dihydroxyspiro[oxolane-5,9'-xanthene]-2-one

1,4-bis(2,4-dihydroxyphenyl)butanedione

4-(2,4-dihydroxy-phenyl)-4-oxo-butyric acid

3-[2-(3-oxo-2-benzofuran-1-ylidene)ethylidene]-2-benzofuran-1-one

(Z)-溴富马酸