Abstract Xanthobilirubic acid, 5-[1, 5-didehydro-3-ethyl-4-methyl-5-oxo-2H-pyrrol-2-ylidene) methyl]-2, 4-dimethyl-1H-pyrrol-3-propanoic acid, its methyl ester, amide, N-methylamide and dimethylamide, and kryptopyrromethenone have been synthesized and characterized spectroscopically. In d 6-DMSO solution all pyrromethenones were monomeric, with lactam and pyrrole N-Hs H-bonded to solvent. In deuteriochloroform, the pyrromethenones ...
