8,9-dihydroxy-2-methyl-4-oxo-5H-pyrano[3,2-c]chromene-10-carboxylic acid

8,9-dihydroxy-4-keto-2-methyl-5H-pyrano[3,2-c]chromene-10-carboxylic acid

8,9-Dihydroxy-2-methyl-4-oxo-4H,5H-pyrano[3,2-c][1]benzopyran-10-carboxylic acid