3-[2-[(Z)-[(5E)-3-(2-carboxyethyl)-5-[(4-ethyl-3-methyl-5-oxo-pyrrol-2-yl)methylene]-4-methyl-pyrrol-2-ylidene]methyl]-5-[(Z)-[(3E,4R)-3-ethylidene-4-methyl-5-oxo-pyrrolidin-2-ylidene]methyl]-4-methyl-1H-pyrrol-3-yl]propanoic acid