Fig. 2. Ramachandran plot of peptide bond torsional angles observed in norbornapeptide structures for (A) l-residues and (B) d-residues. Preferred (red) and allowed (yellow) regions as observed in protein structures are highlighted. The (φ, ψ) torsional angles in the unallowed bottom right portion in (A) are at the α-carbon of l-leucine in 6.
