Aminolactam, N-Aminoimidazolone, and N-Aminoimdazolidinone Peptide Mimics

Among strategies for constraining peptide conformation, the application of 3-amino-γ-lactam (Agl) analogs, the so-called Freidinger-Veber lactams, has played a prominent role in studies of biologically active peptide conformation. Tethering an amino acid side chain to the nitrogen of its neighboring C-terminal residue within a peptide, such lactams constrain backbone ψ- and ω-dihedral angles, as well as side chain χ-torsion angles to induce turn conformation. Reviewing various α-amino lactam analogs as well as their aza-counterparts, the so-called N-amino imidazolinone (Nai) and N-amino imidazolidinone (Aid) residues, this chapter focuses specifically on the synthesis, conformational analysis, and applications of the 5-membered ring congeners and their variants bearing ring substituents.