A great part of the current knowledge about the chemistry and the structure of melanins arises from in vitro studies involving oxidative polymerization of 5,6-dihydroxyindoles under biomimetic conditions. Previous studies carried out on the 5,6-dihydroxyindole-2-carboxylic acid (DHICA), a key intermediate in the biosynthesis of the dark brown eumelanins, had delineated a reaction pathway involving