2- Amino-3,4-dihydroxynaphthalene

Diazotised p-aminophenylarsinic acid is coupled with H acid in alkaline solution and the brownish-violet product cooled and stirred with diazotised diehlorobenzidine. The resultant dyestuff is a glistening dark brown powder, ginng a deep blue solution in water. In place of benzidine or diehlorobenzidine the following may be used tolidine, dianisi-dine, or diaminophenyl urea. Instead of H acid, S-amino-5-naphthol-7-sulphonic acid (J acid), 1 8-aminonaphthol-4-sulphonie acid (S acid or 1 8-dihydroxynaphthalene-8 6-di.sulphonie acid (chronio trope acid) may be employed. 

Fungi like Pyricularia contain a melanin built from 1,8-dihydroxynaphthalene (DHN), called DHN melanin [Butler Day, 1998]. The biosynthetic pathway is short and simple (Fig. 20.1). The origin of the building blocks is not amino acids, but a polyketide originating from acetyl coenzyme A and malonyl coenzyme A. Besides DHN this fungal melanin may contain other poorly characterized constituents. All the enzymes of the DHN melanin biosynthesis pathway are known, have been cloned, except the last one, and are more or less well described [Butler Day, 1998). 

Partial replacement. 2,3-Dihydroxynaphthalene heated 3 hrs. with excess aq. 25%-NHg and 2 moles of NaOH at 150° in a horizontal steel autoclave 3-amino-2-naphthol. Y 83%.—Omission of NaOH favors the replacement of both hydroxyl groups. F. e. s. V. V. Kozlov and I. K. Veselovskaya, 3C. 31, 3030 (1961) G. A. 57, 739g. 

Glucose oxidase, lactate oxidase, L-amino acid oxidase, and alkaline oxidase are immobilized on new films based on 2,6-dihydroxynaphthalene copolymerized with 2-(4-aminophenyl)-ethylamine onto the Pt electrodes... 

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