2,1-Benzothiazine 2,2-Dioxides. 4. Synthesis, Structure, and Analgesic Properties of 4-Hydroxy-1-Methyl-2,2-Dioxo-N-(Pyridin-2-yl)-1H-2λ6,1-Benzothiazine-3-Carboxamides

An improved method has been proposed for the reaction of the methyl ester of 4-hydroxy-1-methyl-2,2-di-oxo-1H-2λ 6 ,1-benzothiazine-3-carboxylic acid with hetarylamines to give 4-hydroxy-1-methyl-2,2-di-oxo-N-(pyridin-2-yl)-1H-2λ 6 ,1-benzothiazine-3-carboxamides and analogs with the similar structure in good yield and purity. X-ray diffraction structural analysis has indicated that these products exist as internal salts. A mass spectral study of these compounds has shown that they have a characteristically enhanced tendency to extrude SO 2 . The pharmacological testing has revealed promising compounds with better analgesic properties than those of the known oxicam drugs.