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
(<5 min) at ambient temperature in various buffers and within a
wide pH range (0.5–14). This approach provides access to a
diverse array of 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.