A mixture of 4-fluoro-N2-phenylbenzene-1,2-diamine (550 mg, 2.7 mmol), (S)-3-benzyloxy-2-tertbutoxycarbonylaminopropionic acid (880 mg, 3.0 mmol), HOAt (410 mg, 3.0 mmol), 4-methylmorpholine (0.65 mL, 5.9 mmol) and N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (580 mg, 3.0 mmol) in DCM (13 mL) was stirred at RT for 18 h. The reaction mixture was partitioned between DCM and a saturated aqueous solution of NaHCO3. The organic fraction was washed with brine, dried (MgSO4), concentrated in vacuo and the resulting residue purified by column chromatography (Si—PCC, gradient 0-30% EtOAc in cyclohexane) to afford [(S)-2-benzyloxy-1-(4-fluoro-2-phenylaminophenylcarbamoyl)ethyl]carbamic acid tert-butyl ester as a red oil (1.1 g, 83%).
