Site-selective S-gem-difluoroallylation of unprotected peptides with 3,3-difluoroallyl sulfonium salts

Bench-stable 3,3-difluoroallyl sulfonium salts proved to be versatile fluoroalkylating reagents for site-selective S-gem -difluoroallylation of cysteine residues in unprotected peptides. The newly added functional groups are poised for ligation.