Synthesis, crystal and molecular structure of Boc-Pro-ΔPhe-Ala-ΔPhe-Ala-OMe: a pentapeptide with a novel β-bend ribbon structure

Neither a helical structure nor a spiral β-bend ribbon structure, but a flat β-bend ribbon is formed by the title compound. Peptides with 2,3-didehydroamino acid esters (α,β-didehydroamino acid esters) such as dehydrophenylalanine (ΔPhe) are of great interest as model compounds for the study of structure-function relationships, since the dehydroamino acids strongly influence the conformation and the enzymatic degradation of peptides. The comparison of the structure of the title compound with that of corresponding Aib-containing peptides is informative