Maxime Ribéraud, Karine Porte, Arnaud Chevalier, Léa Madegard, Aurélie Rachet, Agnès Delaunay-Moisan, Florian Vinchon, Pierre Thuéry, Giovanni Chiappetta, Pier Alexandre Champagne, Grégory Pieters, Davide Audisio, and Frédéric Taran
Journal of the American Chemical Society 2023
DOI: 10.1021/jacs.2c09865Bioorthogonal click-and-release reactions are powerful tools for chemical biology, allowing, for example, the selective release of drugs in biological media, including inside animals. Here, we developed two new families of iminosydnone mesoionic reactants that allow a bioorthogonal release of electrophilic species under physiological conditions. Their synthesis and reactivities as dipoles in cycloaddition reactions with strained alkynes have been studied in detail. Whereas the impact of the pH on the reaction kinetics was demonstrated experimentally, theoretical calculations suggest that the newly designed dipoles display reduced resonance stabilization energies compared to previously described iminosydnones, explaining their higher reactivity. These mesoionic compounds react smoothly with cycloalkynes under physiological, copper-free reaction conditions to form a click pyrazole product together with a released alkyl- or aryl-isocyanate. With rate constants up to 1000 M–1 s–1, this click-and-release reaction is among the fastest described to date and represents the first bioorthogonal process allowing the release of isocyanate electrophiles inside living cells, offering interesting perspectives in chemical biology.
