CYCLIC BETA-AMINO ACIDS AS CONFORMATIONAL CONSTRAINTS

β-amino acids are naturally occurring non-protein amino acids found in several fungal peptide antibiotics. β-amino acids can also tailor stable well-defined secondary structures in peptides. Cyclic β-amino acids can restrain peptide conformations further as the C² and C³ bond is now part of a ring. Data analysis of the crystal structures of these β-amino acids, both for cyclic as well as acyclic amino acid residues, from the 2012 Cambridge structure database reveals that the (φ, ψ) values are spread in the allowed region of the glycine Ramachandran map.