Designing of structures of peptides and proteins by introducing α,β-dehydro-residues in the amino acid sequences

α,β-unsaturated (or dehydro-) amino acids have been found to occur naturally in peptides of microbial origin and in some proteins. The dehydrogenations at C^α and C^β atoms modify the sp³ states of these atoms to sp². As a result, substantial steric effects are introduced, enhancing the unfavorable interactions between the backbone and the side chain. X-ray structural investigations of peptides with dehydro-Phe and dehydro-Leu that have established that very specific secondary structures can be prepared by introducing dehydro-residues are reported. Tables of torsion angles are given