A New Oxidation Pathway of the Neurotoxin 6-Aminodopamine. Isolation and Characterisation of a Dimer with a Tetrahydroiminoethanophenoxazine Ring System.

Article abstract of DOI:10.1016/S0040-4020(01)86599-6

Oxidation of the neurotoxin 6-aminodopamine (1) is known to proceed through the o-quinone 3, which undergoes intramolecular cyclisation to give 5,6-dihydroxyindole (6).In a re-examination of the reaction, we have found that at concentrations of 1 higher than 5 * 10^-3 M a quite different course prevails, leading to the formation of the novel 7-amino-8-(2-aminoethyl)-3-hydroxy-2-oxo-2,3,4,10-tetrahydro<3,4-a>iminoethanophenoxazine (7).Product 7 was formed by aerobic, chemical (persulphate, periodate) or enzymatic (tyrosinase, peroxidase/H2O2) oxidation of 1.On acetylation, 7 afforded the tetraacetate 8.Oxidation of the model compound 5-amino-4-methylcatechol (9) proceeded similarly as that of 1, to give the tetrahydrophenoxazinedione 11.