Rapid Electrophilic Cysteine Arylation with Pyridinium Salts

Abstract

Here, we present a series of fluorinated cationic reagents that enable rapid arylation of cysteine under mild conditions compatible with proteins and peptides. The highly polarized C–F bond and attractive nucleophile–electrophile Coulombic interactions substantially accelerate cysteine arylation, leading to unusually high rate constants on the order of 100 M–1·s–1 and allowing for equimolar labeling of substrates at micromolar concentrations. The synthetic modularity of this approach promotes the direct coupling of structurally diverse phenol-containing functional motifs to cysteine residues of biomacromolecules with high efficiency. This user-friendly chemistry enables fast bond formation between commonly used bioconjugation partners, thus greatly streamlining the synthetic chemistry workflow, and can be easily developed as convenient kits for chemical biology and medicinal chemistry applications.

Cu-catalyzed arylation of S-tosyl peptides with arylboronic acids

“…Examples include cysteine arylation with electron-deficient aryl halides for the S N Ar reaction ( e.g. perfluoroarene, 8–10 fluorinated pyridinium salts, 11 and aryl thioethers 12 ) and activated arene species ( e.g. hypervalent iodine reagent 13 and diazo compounds 14,15 ).…”

Chemical technology principles for selective bioconjugation of proteins and antibodies

“…4). 41 Furthermore, polarized double bonds have led to multiple Cys-selective bioconjugation reagents. The regulation of LUMO energy through electron-withdrawing groups or strain has been examined to tune reactivity and selectivity in such cases.…”

Traceless Peptide and Protein Modification via Rational Tuning of Pyridiniums

“…Achieving a versatile reaction platform requires a good structural diversity and a thorough understanding of the structure–activity relationship (SAR), which by regulating the stability and cleavability of the bioconjugates and stapled peptides could enable fine-tuning of biological activity. Our group has recently investigated the unique reducibility and biophysical properties of positively charged compounds, such as sulfoniums and pyridiniums, making them promising candidates for bioconjugation. − Aromatic nucleophilic substitute (S N Ar) reactions have been extensively researched and applied within the realm of bioconjugation chemistry, with reports showcasing the substantial potential of such reagents when employing nitrogen-containing heterocycles and their onium salts as conjugation reagents. − Drawing on the in-depth understanding of these electron-deficient compounds, we identified that pyridiniums with halogen as a leaving group would be a suitable platform for tunable bioconjugation through the S N Ar. The electrophilicity of the halo-pyridiniums could be predicted and finely tuned by altering the effective nuclear charge, owing to the well-understood electron effects of substituents on aromatic rings .…”