N‑Aminoimidazolidin-2-one Peptidomimetics

The synthesis of N-aminoimidazolidin-2-one (Aid) peptidomimetics has been achieved by alkylation of the urea nitrogen of a semicarbazone residue using ethylene bromide. The Aid scaffold combines electronic and structural constraints to rigidify the peptide backbone in the equivalent of an aza variant of a Freidinger–Veber lactam. The syntheses and isolation of 25 Aid peptides, including eight GHRP-6 analogues, are reported to demonstrate the utility of this method for controlling conformation.