3-(2,5-Dioxo-2,5-dihydropyrrol-1-yl)propionic acid 2,5-dioxopyrrolidin-1-yl ester (787 mg, crude) was dissolved in DMF (15 ml). 8-Aminooctanoic acid (350 mg) and DIPEA (0.45 ml) was added. The mixture was stirred under nitrogen at room temperature over night. The mixture was concentrated. The residue was dissolved in EtOAc and extracted with 0.1 N HCl (2×). The phase separation was not easy. The organic layer was washed with brine (2×), dried (Na2SO4) and concentrated to give a white solid. LC-MS, M/z: 311.34 (M+1).
