4-chloro-2,5-diformyl-pyrrole-3-carboxylic acid

5,6-二羟基-2-吲哚甲酸

2-(5,6-dihydroxy-1H-indol-2-yl)-1H-indole-5,6-diol

2,2'-dicarboxy-5,5',6,6'-tetrahydroxy-4,4'-biindolyl