Formed during alkaline oxidation of uric acid with H2O2 or KMnO4. Prepn and structure: Brandenberger, Helv. Chim. Acta 37, 641 (1954); Brandenberger, Brandenberger, ibid. 37, 2207 (1954); Piskala, Gut, Collect. Czech. Chem. Commun. 27, 1572 (1962). Metabolism: Chelbova et al., Biochem. Pharmacol. 19, 2785 (1970); Cihak, Sorm, ibid. 21, 607 (1972).