Photo-accelerated "click" reaction between diarylsydnones and ring-strained alkynes for bioorthogonal ligation.

We constructed a library of diarylsydnone (DASyd) candidates in search of a photoclickable reaction toward alkynes, enabling an ultra-accelerated reactivity, while suppressing the background cycloaddition in the dark. The in vitro and in vivo protein labelling experiments revealed that the photo-accelerated DASyd-alkyne cycloaddition exhibits robust selectivity.