The invention provides a palladium-promoted hydrolytic polypeptide cleavage process which selectively cleaves the polypeptide at a Cys-His cleavage site comprising solubilizing the polypeptide in a reaction mixture comprised of a palladium promoter dissolved in a high-concentration formic acid, wherein the concentration of the formic acid in the reaction mixture is between about 1 to about 22 molar.