2-Butenoic acid, 4-((2-(acetylamino)-1-oxo-3-phenylpropyl)amino)-, (2S-trans)- 4-((N-Acetylphenylalanyl)amino)-but-2-enoic acid methyl ester 89711-04-6 Mapheb Methyl 4-((N-acetylphenylalanyl)amino)but-2-enoate