6-Hydroxy-5H-pyrrolo[3,4-b]pyridine-5,7(6H)-dione
7-Hydroxy-1H-pyrrolo[2,3-c]pyridine-3-carboxylic acid
5-Hydroxy-1,3-dihydro-2H-pyrrolo[2,3-b]pyridin-2-one
