Efficient and direct solid phase synthesis of ketomethylenimino and ketomethylenamino peptides

The aim of this study is the synthesis of pseudopeptides on solid supports, in order to quickly obtain modified peptides. We report a convenient step-by-step synthesis of ketomethylenimino ψ[CO–CHN] and ketomethylenamino ψ[CO–CH2–NH] peptides. The key is the reaction between the free amino terminus of the supported peptide and a glyoxal-modified amino acid, leading to a ketomethylenimino bond, which can be reduced to a ketomethylenamino bond.