Conformations of cyclic octapeptides. 4. Diastereomers of cyclo(Gly-Pro-Phe-Ala-Asn-Ala-Val-Ser)

Stereoisomers of cyclo(Gly-Pro-Phe-Ala-Asn-Ala-Val-Ser) were synthesized. NMR studies of their solution conformations, focusing on peptide N-H solvent exposure, were made. These indicated that a single proline residue in the cyclic octapeptide ring is insufficient constraint to stabilize the backbone conformations that were previously established for cyclo(Gly-Pro-Phe-Ala)2.