The introduction of a cyclic amino acid in a peptide is one of the best methods to rigidify a strand. A general approach towards a new class of seven-membered ring amino acids is described starting from (S)-tribenzyl glutamic acid γ-aldehyde, which reacts with β-keto phosphonates to generate the Horner–Wadsworth–Emmons product. In the presence of H2 and a Pd catalyst, a four-step process occurs involving