Selective Labeling of Peptides with o‐Carboranes via Manganese(I)‐Catalyzed C−H Activation

A robust method for the selective labeling of peptides via manganese(I) catalysis was devised to achieve the C‐2 alkenylation of tryptophan containing peptides with 1‐ethynyl‐o‐carboranes. The manganese‐catalyzed C−H activation was accomplished with high catalytic efficiency, and featured low toxicity, high functional group tolerance and excellent E‐stereoselectivity. This approach unravels a promising tool for the assembly of o‐carborane with structurally complex peptides of relevance to applications in boron neutron capture therapy.