Ascorbate as a pro-oxidant: mild N-terminal modification with vinylboronic acids

Abstract

We describe divergent reactivity of vinylboronic acids for protein modification. In addition to previously reported copper-catalyzed backbone N–H modification, ascorbate in air mediates N-terminal functionalization with the same vinylboronate reagents. This mild and selective aqueous reactivity enables selective single-modification of the B chain of human insulin.