2]thiazine-3-carboxamide 1,1-dioxide; 1) were synthesized, and various chemical transformations were investigated. Both selective hydrolysis and reaction of 1′-N-methyltenoxicam (5) with a variety of N-nucleophiles were performed (Scheme 1). Also, five new 4-O-acyl derivatives 10 were prepared as potential prodrugs (Scheme 2). The 4-chloro derivatives of 1 and its analog 8 could be successfully transformed