5,6-Dihydroxyindole
5,6-Dihydroxyindole, also known as aminochrome, is a chemical compound with the molecular formula C8H7NO2. It is an intermediate in the production of the biological pigment eumelanin. 5,6-Dihydroxyindole is biosynthesized from L-dopachrome in a reaction catalyzed by a tyrosinase enzyme and is further converted into indole-5,6-quinone. In humans, 5,6-dihydroxyindole is involved in the metabolic disorder hawkinsinuria.
In some insects, 5,6-dihydroxyindole is a reactive compound that is produced as a component of defense responses and has antibacterial and antifungal activity.
A laboratory synthesis of 5,6-dihydroxyindole can be accomplished starting from 3,4-dibenzyloxybenzaldehyde. This compound is condensed with nitromethane in a Henry reaction, followed by nitration, reduction of the nitro groups, and hydrogenolysis of the benzyl protecting groups.