Frangulanine is a peptide alkaloid, with a 14 membered macrocyclic ring, from Hovenia dulcis THUNB. The X-ray analysis of frangulanine derivative and the synthetic study revealed the conformation of frangulanine as shown in Fig. 1 and Fig. 2. The tetrapeptide, Ile-Hyleu-Leu-Tyr, a hypothetical intermediate of frangulanine biosynthesis, was also synthesized.