Synthesis and Biological Evaluation of New 1,4-Thiazine Containing Heterocyclic Compounds

4H-1,4-benzothiazines are prepared by condensation of 2-aminobenzenethiol with β-diketones / β-ketoesters in dimethyl sulfoxide. These prepared benzothiazines are used as base to prepare ribofuranosides by treating them with β-D-ribofuranosyl-1-acetate-2,3,5-tribenzoate. 4H-1,4-benzothiazines, on refluxing with hydrogen peroxide in glacial acetic acid gave 4H-1,4- benzothiazine-1,1-dioxides (sulfones). Their antioxidant and antimicrobial activity have also been evaluated. Structure of the synthesized compounds have been established by their spectral investigation.