4-Hydroxy-2H-1, 2-benzothiazine-3-carboxylic acid 1a was reacted with 2 equivalents of dicyclohexylcarbodiimide (DCC) to give 2-cyclohexyl-3-cyclohexylimino-4,5-dihydro-1H-imidazo [1,5-b][1,2] benzothiazine-10, 10a-dyhydro-1,10-dione 5,5-dioxide 2a and dicyclohexylurea (DCU). On the other hand 2-substituted-4-hydroxy-2H-1, 2-benzothiazine-3-carboxylic acid 1,1-dioxide 1b or c was reacted with DCC to give 2-cyclohexylimino-3-cyclohexyl-5-alkyl-4-oxo-2,5H-1,3-oxazino [5,6-c]-1,2-benzothiazine 6,6-dioxide 2b or c and DCU.