Direct entry to peptidyl ketones via Sm[I.sub.2]-mediated C-C bond formation with readily accessible N-peptidyl oxazolidinones

A new method is described for preparing peptidyl ketones by using a Sm[I.sub.2]/[H.sub.2]O mediated coupling of N-peptidyl oxazolidinones with electron-deficient alkenes. This new method is an alternative means for ligating two small peptides through a C-C bond-forming step.