4-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl) butanoic acid4-(1,3-Dioxo-1,3-dihydro-isoindol-2-yl)-butyric acid4-(1,3-Dihydro-1,3-dioxo-2H-isoindol-2-yl)butanoic acid4-(Phthalimid-1-yl)butanoic acid4-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)butanoic acid