vinylsulfonamides were synthesized and screened for site-selective modification of the ε-amino group of lysine-bearing free α-amine residues. N-methyl-N-phenylethenesulfonamide has emerged as an applicable reagent and has been developed for efficient and highly selectivemodification of the lysine residue of native peptides in the presence of a free N-terminus via aza-Michael addition. We demonstrated that functional