Knowledge Bank

The solution conformations of three peptides containing dehydrophenyl alanine ($\Delta Z-Phe$) have been determined from their NH-, CH- and $C=O$. stretching vibrational circular dichroism spectra. We have found that the peptides $Ac-\Delta Z-Phe-L-Ala-OMe(1),Ac-\Delta Z-Phe-\Delta Z-Phe-L-Ala-OMe(2)$. and $Boc-L-Ala-\Delta Z-Phe-Gly-\Delta Z-Phe-L-Ala-OMe(3)$ are all stabilized in chloroform solution by intramolecular hydrogen bonds. The conformation of the $C10$-ring in peptide 1 and C10-ring (type I $\beta$-turn) in peptide 2 involving the $\Delta Z-Phe$ residues is determined by the formation of a $C5$-ring in the terminal L-Ala residue. Peptide 3 assumes several intramolecularly hydrogen-bonded conformations including a type III $\beta$-turn