Hydrolysis of activated esters, e.g., picolinic acid and alpha-amino acid esters, in the presence of Cu2+ salts is a stoichiometric process because products of this reaction bind the catalytic metal ion substantially stronger than starting materials do. Herein we report improved ester substrates, which are cleaved in the presence of catalytic amounts of Cu2+; 55 turnovers of hydrolysis are observed for the best substrate, acetic acid 2-hydroxypyridine ester. We demonstrate that this reaction can be used for sensitive and selective detection of Cu2+ by using both absorption and fluorescence spectroscopy.