A method is provided for the preparation of compounds of the formula (R.sup.1)(R.sup.2)NC(.dbd.X)S(O).sub.nR.sup.3 or (R.sup.1)(R.sup.2)NC(.dbd.X)OS(O).sub.nR.sup.3, wherein R.sup.1, R.sup.2 and R.sup.3, X and n have any of the meanings defined in the specification. A method is also provided for the detection and quantitation of compounds of the formula (R.sup.1)(R.sup.2)NC(.dbd.X)OS(O).sub.nR.sup.3. A method to link a therapeutic agent to a compound that is conjugated to glutathione is also provided for the purpose of improving the therapeutic properties of the therapeutic agent. Novel compounds, intermediates, pharmaceutical compositions and methods of use are also provided.