Application of Reductive Samariation to the Synthesis of Small Unnatural Peptides.

Considering that the amide NH groups are neither protected nor deprotonated, reductive samariation in the presence of a carbonyl substrate is a remarkably efficient method for the formation of a C-C bond. This was shown for a series of dipeptides and a tripeptide [Eq. (a)]. For the latter the product was obtained in a good yield of 50 %, despite the presence of three amide protons.