STEREOCHEMICAL STUDIES ON CYCLIC PEPTIDES .2. MOLECULAR STRUCTURE OF CYCLOTRIPROLYL

The paper deals with the attempts to predict the molecular structure of cyclotriprolyl, a cyclic peptide which has been synthesized recently. Model building shows that, in this structure, all the peptide units have to be in the cis-conformation. It is further found that the structure derived using cis-peptide units having the same dimensions as the Pauling-Corey trans-unit, besides containing extremely short Ha ··· Ha non-bonded interaction, also makes the proline ring-closure impossible. Stereochemical studies using contact criteria show that a satisfactory structure is possible with cis-peptide units having a non-planarity Δω of approximately -25°. © 1968.