With their low toxicity, high functional group tolerance and stability in biocompatible media, hypervalent iodine reagents have recently emerged as powerful tools for late-stage peptide and protein functionalization. In 2019, our group reported the synthesis of vinylbenziodoxolone reagents (VBX) by stereoselective addition of phenols, sulfonamides and thiols nucleophiles onto ethynylbenziodoxolones (EBX). The VBX were shown to be bench-stable and the enhanced reactivity of the hypervalent bond allowed their use as electrophiles in palladium-catalyzed cross-couplings at room temperature. During this work, an N-and C-protected tyrosine could be used as a nucleophile, but the reaction conditions developed for small organic molecules were not compatible with peptides and proteins. Moving from protected amino-acids to native peptides is challenging, as they contain multiple reactive nucleophilic functionalities and require aqueous buffers for solubilization, which are attenuating the reactivity of the residues and could degrade the reagents. Formation of S-VBX reagents from cysteine under physiological conditions was previously reported by our group. As a harder and less nucleophilic residue, tyrosine usually displays a lower reactivity with electrophiles than the soft and highly nucleophilic cysteine. Indeed, no tyrosine functionalization had been observed under the conditions developed for S-VBX formation. Nevertheless, free cysteine residues are occurring only rarely in peptides and proteins, most of them form disulfide bonds, which usually do not react with EBX reagents. It should be therefore possible to selectively target tyrosine if adequate conditions could be developed and other nucleophilic amino acids would not interfere. In this work, we report a tyrosine-selective modification of peptides with EBX 2a under mild and biocompatible conditions (Scheme 1c). With the exception of cysteine, all nucleophilic residues present in peptides were tolerated, and the method could be used for both synthetic peptides and natural products. Preliminary results indicate that the method can also be used with proteins with surface accessible tyrosine residues. The stable O-VBX conjugates were then used as a platform for further orthogonal modifications via a palladium-catalyzed Suzuki-Miyaura cross-coupling and a metal-free Strain-Promoted Alkyne-Azide Cycloaddition (SPAAC), providing a wide range of labelled biomolecules. Using this methodology, native streptavidin was modified to enable thiol-mediated cellular uptake.