Total eighteen kinds of Δ1-, Δ2-, and Δ3-dehydrotripeptides (DHP) containing of a ΔPhe and two chiral α-amino acid residues were synthesized and the diastereomeric mixture of DHP were subjected to the HPLC separation. From the results and the 1H NMR spectral data, it was found to be significant relationship between the separation and the conformational structure of DHP.