The application of a zinc carbenoid-mediated chain-extension reaction to a functionalized peptide isostere is reported. The cleavage site of human CVM protease was utilized as a target for testing the synthetic methodology. The utility of this chain-extension reaction is demonstrated in the preparation of an amino acid-derived α-unsubstituted γ-keto ester, which is incorporated into a framework that mimics a tetrapeptide. The identification of a ...