Direct entry to peptidyl ketones via SmI2-mediated C-C bond formation with readily accessible N-peptidyl oxazolidinones

In this work, a new method for the preparation of peptidyl ketones is presented employing a SmI(2)/H(2)O-mediated coupling of N-peptidyl oxazolidinones with electron-deficient alkenes. The requisite peptide imides were easily prepared by solution-phase peptide synthesis starting from an N-acyl oxazolidinone derivative of an amino acid. Importantly, they could be used directly in the C-C bond-forming step without the need for further functionalization. Coupling of these peptide derivatives with a second peptide possessing an N-terminal acryloyl group leads to ketomethylene isosteres of glycine-containing peptides. This method represents an alternative means for ligating two small peptides through a C-C bond-forming step.