A solution of phenylacetic acid (89 mg, 0.65 mmol, 1 equiv) in DMF (10 mL) was added to EDCI (188 mg, 0.98 mmol, 1.5 equiv.). After stirring for 20 min, 2-[(4′-Amino-biphenyl-4-carbonyl)-amino]-pentanedioic acid di-tert-butyl ester (297 mg, 0.65 mmol, 1 equiv.) was added, followed by the addition of Et3N (0.23 mL, 1.64 mmol, 2.5 equiv.) and DMAP (16 mg, 0.13 mmol, 20%). The reaction mixture was allowed to stir at room temperature overnight. Reaction was complete as determined by TLC. DMF was removed and the residue was dissolved in EtOAc. The organic layer was washed with H2O and brine, and then dried over MgSO4. After solvent was evaporated, the crude residue was purified by HPLC to give 45 mg of 2-[(4′-Phenylacetylamino-biphenyl-4-carbonyl)-amino]-pentanedioic acid di-tert-butyl ester in 12% yield. MS (ESI) m/z 573.
