Manipulating the Click Reactivity of Dibenzoazacyclooctynes: From Azide Click Component to Caged Acylation Reagent by Silver Catalysis

Abstract Strain‐promoted azide–alkyne cycloaddition using dibenzoazacyclooctyne (DBCO) is widely applied in copper‐free bioorthogonal reactions. Reported here is the efficient acid‐promoted rearrangement and silver‐catalyzed amidation of DBCO, which alters its click reactivity robustly. In the switched click reaction, DBCO, as a caged acylation reagent, enables rapid peptide/protein modification after decaging facilitated by silver catalysts, rendering site‐specific conjugation of an IgG antibody by a Fc‐targeting peptide.