Dihydroxyanthranilic acid as a precursor of nicotinic acid.

A MIXTURE of 400 mgm. of o-aminoveratric acid (prepared by the method of Pschorr and Sumuleanu1), 100 mgm. of red phosphorus and 8 ml. of hydriodic acid (sp. gr. 1.7) was heated in a sealed tube at 100° for eight hours and then at 105° for two hours. The hydriodic acid salt of 2-amino-3,4-dihydroxybenzoic acid crystallized on cooling. After filtration, this product was recrystallized from a small amount of hydriodic acid containing water and obtained as macroscopic prismatic needles (m.p. 220°; found: N, 4.29; C7H8O4NI requires N, 4.71 per cent). The hydriodide of dioxyanthranilic acid was easily dissociated by washing with a larger amount of water, and the free acid was recrystallized from alcohol (m.p. 174°; found: N, 8.05; C7H7O4N requires N, 8.29 per cent).