We describe anew technique in protein synthesis that extends the existing repertoire of methods for protein modification:Achemoselective reaction that induces reactivity for as ubsequent bioconjugation. An azide-modified building blockr eacts first with an ethynylphosphonite through aS taudinger-phosphonite reaction (SPhR) to give an ethynylphosphonamidate.T he resulting electron-deficient triple bond subsequently undergoes ac ysteine-selective reaction with proteins or antibodies.W ed emonstrate that ethynylphosphonamidates display excellent cysteine-selective reactivity combined with superior stability of the thiol adducts,w hen compared to classical maleimide linkages.T his turns our technique into av ersatile and powerfult ool for the facile construction of stable functional protein conjugates.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.Figure 4. a) Synthetic scheme for phosphonamidate attachmentofthe Cy5f luorophore to trastuzumab(anti-Her2 antibody) to generate an AFC. b) Immunostaining of fixed cells either over-expressing the cell-surface receptor Her2 (BT474) or exhibiting low Her2 expression levels (MDAMB468). The merged images show the signal from the DNA stain DAPI in blue and the Cy5signal in red. Scale bar:10mm. c) Synthetic scheme for the attachmento fphosphonamidite-modified cCPPs 8 and 9 to aeGFP mutant with asingle addressable cysteine. d) Fluorescence imaging of HeLa cells after incubation with eGFP alone and eGFP-cTat at 50 mm.I mages show the GFP channel in green and the Hoechst 33342 nuclear stain in blue. Scale bar:2 0mm. Forfurther information see the SupportingInformation. Angewandte Chemie Communications

No abstract

Mesoionic carbenes (MICs) are currently hugely popular as ligands, and triazolylidenes are arguably the most prominent classes of such MICs. Mesoionic carbenes with ferrocenyl substituents are presented that can act as metalloligands for the generation of heteromultimetallic iridium(I) and gold(I) complexes. The ferrocenyl substituents allow for reversible oxidation of these heteromultimetallic complexes, and these oxidation steps have a strong influence on the donor properties of the MICs. Tolman electronic parameters (TEP) determined from analysis of the iridium-carbonyl complexes show that the neutral ferrocenyl-MIC ligands are stronger donors than the imidazolylidene based carbenes, the one-electron oxidized ferrocenyl MICs are in the range of the tricyclohexyl phosphines and the two-electron oxidized forms, which are electron-poor, lie in the range of triphenyl phosphines. Taking advantage of the generation of these electron-poor MICs, we show their gold(I) complexes are potent catalysts for the synthesis of oxazolines, with complexes of the oxidized MIC ligands, without any additional additive, outperforming their neutral counterparts by almost a factor of ten. These results thus present the first examples of MIC ligands that are reversibly electronically tunable, and show the potential of the oxidized MIC ligands in types of catalysis where electron-poor ligands are necessary. The potential of MICs for molecular electroactive materials is also shown.