1,9-Isothiazoleanthrone-2-carboxylic acid 4-27-00-04342 (Beilstein Handbook Reference) 6-Oxo-6H-anthra(9,1-cd)isothiazole-3-carboxylic acid 6H-Anthra(9,1-cd)isothiazole-3-carboxylic acid, 6-oxo- 82-63-3 BRN 0258309