Unprecedented acceleration of zirconium(IV)-assisted peptide hydrolysis at neutral pH

4,13-Diaza-18-crown-6 substantially increases the rate of zirconium(IV) hydrolysis of unactivated peptide amide bonds under near-physiological conditions of temperature and pH. In the presence of this azacrown ether, ZrCl4 efficiently hydrolyses both neutral and negatively charged peptides (pH 7.0-7.3, 37-60 degreesC).