To demonstrate the utility of these SPGs, a tyrosine reactive covalent inhibitor of the enzyme Bruton Tyrosine Kinase (BTK) was developed. BTK is a well-known target for the treatment of leukemia and lymphomas and is critical for B-cell proliferation in cancer. Currently, all FDA approved BTK inhibitors are covalent inhibitors containing an acrylamide that reacts with Cys481. Mutations, however, of Cys481 have led to resistance to covalent BTK inhibitors ; thus recently, more reversible inhibitors have entered various stages of clinical trials. Given the success of covalent BTK inhibitors, covalent inhibitors or probes that react with tyrosine or lysine residues would be beneficial.