Pyloricidin C (I) is isolated from the fermentation broth of Bacillus sp. HC-70. Enzymatic hydrolysis of the N-terminal leucyl moiety of (I) by the action of actinase E leads to dipeptide (II). N-Boc-(S)-2-amino-4-pentenoic acid (III) is activated as the corresponding succinimidyl ester (IV) upon treatment with N hydroxysuccinimide and DCC. Then, coupling of dipeptide (II) with the active ester (IV) furnishes the tripeptide derivative (V). Finally, the N-Boc protecting group of (V) is removed by treatment with HCl in EtOAc to yield the title compound.