Boronic Acid Mediated Coupling of Catechols and N‑Hydroxylamines: A Bioorthogonal Reaction to Label Peptides

An irreversible, three-component assembly with 2-formylphenylboronic acid, catechol, and N-hydroxylamines was achieved in aqueous media. The boronate ester product was formed with substituted catechols including l-DOPA. Assembly was found to be orthogonal to common biological functional groups and both copper­(I)-catalyzed alkyne–azide cycloaddition and aminoether/carbonyl condensations. Boronate ester formation and aminoether condensation were achieved in one pot with a hexameric peptide.