Exploring the chemistry of penicillin as a β-lactamase-dependent prodrug

Abstract

The penam nucleus can be modified to behave as a β-lactamase-dependent ‘prodrug’ by incorporation of a vinyl ester side chain at the 6-position. Enzyme-catalysed hydrolysis of the β-lactam ring uncovers the thiazolidine-ring nitrogen as a nucleophile that drives a rapid intramolecular displacement on the side chain. Attachment of 7-hydroxy-4-methylcoumarin as the releasable group of this side chain generated a penicillin structure that can function as a fluorescence-based reporter substance/diagnostic for the presence of low levels of β-lactamase enzyme in solution. Mechanistic details of the reaction pattern are documented and the scope and limitations of exploiting the structural modification are discussed.