1H-Pyrrole-2,5-dione, 1-(4-(4-((2,5-dioxo-1-pyrrolidinyl)oxy)-4-oxobutyl)phenyl)- 79886-55-8 NSC 344484 PS50 Cpd SMPB Succinimidyl 4-(4-maleimidophenyl)butyrate