1,1-dimethylethyl [2-({[4-(hydroxymethyl)phenyl]carbonyl}amino)-4-(2-thienyl)phenyl]carbamate (650 mg, 1.531 mmol), BOP (1016 mg, 2.297 mmol), dimethylphosphinic acid (216 mg, 2.297 mmol), DMAP (10 mg, 0.082 mmol) and DIPEA (0.401 mL, 2.297 mmol) were stirred in DMF (8 mL) at room temperature overnight. Additional BOP (2370 mg, 5.36 mmol), DIPEA (0.936 mL, 5.36 mmol), dimethylphosphinic acid (504 mg, 5.36 mmol) and DMAP (20 mg, 0.164 mmol) were added and stirring continued for 24 hours. Additional BOP (1016 mg, 2.297 mmol), DIPEA (0.401 mL, 2.297 mmol) and dimethylphosphinic acid (216 mg, 2.297 mmol) were added and stirring continued for 6 hours. Saturated NaHCO3 was added and the products extracted into EtOAc (×2). The combined organic extracts were dried over MgSO4 and concentrated in vacuo. Purification of the residue by MPLC (0-20% MeOH-EtOAc) gave [4-({[2-({[(1,1-dimethylethyl)oxy]carbonyl}amino)-5-(2-thienyl)phenyl]amino}carbonyl)phenyl]methyl dimethylphosphinate as a yellow gum. 1H-NMR (600 mHz, DMSO-d6) δ 9.90 (s, 1H), 8.72 (s, 1H), 7.96 (d, J=8.4 Hz, 2H), 7.90 (d, J=2.4 Hz, 1H), 7.58 (d, J=8.4 Hz, 1H), 7.53 (d, J=8.4 Hz, 2H), 7.49 (m, 2H), 7.43 (dd, J=3.6 and 1.2 Hz, 1H), 7.10 (dd, J=4.8 and 3.6 Hz, 1H), 5.02 (d, J=8.4 Hz, 2H), 1.46 (d, J=13.8 Hz, 6H), 1.42 (s, 9H). MS: cal'd 401 (MH+-Boc), exp 401 (MH+-Boc).
