4,6-Dimethyl-3-oxo-2,3-dihydroisothiazolo(5,4-b)pyridine-2-carboxylic acid methyl ester 97248-90-3 Isothiazolo(5,4-b)pyridine-2-carboxylic acid, 2,3-dihydro-4,6-dimethyl-3-oxo-, methyl ester