A new synthetic route to (E)--phenyl-␣,-dehydroalanine (⌬ E Phe)-containing peptide was presented via photochemical isomerization of the corresponding (Z)--phenyl-␣,-dehydroalanine (⌬ Z Phe)-containing peptide. By applying this method to Boc-Ala-⌬ Z Phe-Val-OMe (Z-I: Boc, t-butoxycarbonyl; OMe, methoxy), Boc-Ala-⌬ E Phe-Val-OMe (E-I) was obtained. The identification of peptide E-I was evidenced by 1 H-nmr, 13 C-nmr, and uv absorption spectroscopy, elemental analysis, and hydrogenation. The conformation of peptide E-I in CDCl 3 was investigated by 1 H-nmr spectroscopy (solvent dependence of NH chemical shift and difference nuclear Overhauser effect). Interestingly, peptide E-I differed from peptide Z-I in the hydrogen-bonding mode. Namely, for peptide Z-I, only Val NH participates in intramolecular hydrogen bonding, which leads to a type II -turn conformation supported by hydrogen bonding between CO(Boc) and NH (Val). On the other hand, for peptide E-I, two NHs, ⌬ E Phe NH and Val NH, participate in intramolecular hydrogen bonding. In both peptides, a remarkable NOE (ϳ11-13%) was observed for Ala C ␣ H-⌬Phe NH pair. Based on the nmr data and conformational energy calculation, it should be concluded that peptide E-I takes two consecutive ␥-turn conformations supported by hydrogen bonding between CO(Boc) and NH(⌬ E Phe), and between CO(Ala) and NH(Val) as its plausible conformation.