5.6- Dihydroxy-2-methylindole, oxidation

In another study (82JOC5258), air oxidation of a-methyl-3,4-dihydroxyphenyl-alanine ethyl ester was shown to lead to ethyl 5,6-dihydroxy-2-methylindole-3-carboxylate 31 via a remarkable 1,2-migration of the ethoxycarbonyl group of the aminochrome intermediate (Eq. (4)). The structure of the product was confirmed by an independent synthesis ... 

Young TE, Babbitt BW, Wolfe LA (1980) Melanin. 2. Electrochemical Study of the Oxidation of a-Methyldopa and 5,6-Dihydroxy-2-methylindole. J Org Chem 45 2899... 

The oxidation of a number of catecholamines including adrenaline, noradrenaline, a-methylnoiadrenaline, dopamine and isoprenaline has been studied by electrochemical techniques [106, 107]. In 1 m sulphuric acid, adrenaline was reversibly oxidised to adrenaline quinone (43) and it was shown by cyclic voltammetry that under these conditions negligible cyclisation to adrenochrome occurred [106]. At pH 3, however, there was considerable cyclisation, and, as well as the adrenaline-adrenaline quinone (43) couple, the leucoadrenochrome (13)-adrenochrome and the 5,6-dihydroxy-A-methyl-indole (44)-A-methylindole-5,6-quinone (45) couples could be detected and... 

A study of the reaction of cysteine and its ethyl ester with adenochrome (130) is also reported to give, along with 5,6-dihydroxy-1-methylindole, the pyrrolo[2,3-H][l,4]benzothiazine (132), a member of a novel heterocyclic sytem, which probably arises by the dehydration and oxidative ring-closure of the addition product (131). 

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