Scheme 1. Schematic representation of Cys–Met bis-alkylation and proximity-promoted protein labeling with a sulfonium tethered peptide. (A) Deming et al.'s report of selective methionine alkylation and our previous report of chemoselective methionine bis-alkylation. (B) Peptide macrocyclization through cysteine and methionine bis-alkylation. (C) Ligand induced protein conjugation using the Cys–Met macrocyclization method.
