To a solution of 2-((S)-3-((S)-1-(4-bromophenyl)ethyl)-6-(4-fluorophenyl)-2-oxo-1,3-oxazinan-6-yl)acetic acid (0.0259 g, 0.059 mmol) in DMF (2 mL) was added HATU (0.2298 g, 0.60 mmol), DIPEA (0.5 mL), and 0.8 M NH3 in THF (4 mL). The mixture was stirred at rt for 2 d. After the solvents were removed in vacuo, the residue was purified by reversed-phase HPLC (SunFire™ Prep C18 OBD™ 5 μm 19×50 mm column, 10%→90% CH3CN/H2O, 0.1% CF3COOH over 8 min and then 90% CH3CN/H2O, 0.1% CF3COOH over 2 min, flow rate 20 mL/min) to afford 0.0146 g (57%) of 2-((S)-3-((S)-1-(4-bromophenyl)ethyl)-6-(4-fluorophenyl)-2-oxo-1,3-oxazinan-6-yl)acetamide. LC-MS Method 1 tR=1.55 min, m/z 435, 437 (MH+), 391, 393; 1H NMR (400 MHz, CD3OD) δ 7.30-7.26 (m, 2H), 7.19-7.16 (m, 2H), 7.04-6.99 (m, 2H), 6.74 (d, J=8.5 Hz, 2H), 5.39 (q, J=7.0 Hz, 1H), 3.06-3.01 (m, 1H), 2.72-2.58 (m, 3H), 2.42-2.34 (m, 1H), 2.26-2.19 (m, 1H), 1.41 (d, J=7.0 Hz, 3H); 19F NMR (376 MHz, CD3OD) δ −116.70 (m).
