Organometallic Gold(III) Reagents for Cysteine Arylation

An efficient method for chemo­selective cysteine arylation of unprotected peptides and proteins using Au­(III) organometallic complexes is reported. The bioconjugation reactions proceed rapidly (S-aryl bioconjugates including fluorescent dye, complex drug molecule, affinity label, poly­(ethylene glycol) tags, and a stapled peptide. A library of Au­(III) arylation reagents can be prepared as air-stable, crystalline solids in one step from commercial reagents. The selective and efficient arylation procedures presented in this work broaden the synthetic scope of cysteine bioconjugation and serve as promising routes for the modification of complex biomolecules.