We are interested in a-diazophosphonic acids (3) as possible photoaffinity labeling reagents which may surmount these limitations. Our intention is that they may mimic the analogous phosphates (4) and make available a wide range of potential labeling reagents. In this communication we describe the synthesis and characterization of three diazophosphonic acids: the diethylsulfamoyl, diisopropylphosphono, and dimethylcarbamoyl derivatives of ...