The structure of fermentation product A 19009 was reinvestigated by 13C and 1H NMR spectroscopy and established by independent synthesis to be N2-L-alanyl-N3-fumaramoyl-L-2,3-diaminopropanoic acid (2), i.e. a structure isomeric with the originally proposed structure 1. In contrast to 1 which also was synthesized, 2 has a very low activity against Trichomonas vaginalis.