[CH3:1][CH:2]([C@H:4]1[CH2:9][N:8]([C:10]2[CH:15]=[CH:14][C:13]([N+:16]([O-:18])=[O:17])=[C:12]([O:19][CH3:20])[CH:11]=2)[CH2:7][CH2:6][N:5]1C(OC(C)(C)C)=O)[CH3:3].C(O)(C(F)(F)F)=O>C(Cl)Cl>[CH3:3][CH:2]([C@@H:4]1[NH:5][CH2:6][CH2:7][N:8]([C:10]2[CH:15]=[CH:14][C:13]([N+:16]([O-:18])=[O:17])=[C:12]([O:19][CH3:20])[CH:11]=2)[CH2:9]1)[CH3:1]1,1-Dimethylethyl (2S)-2-(1-methylethyl)-4-[3-(methyloxy)-4-nitrophenyl]-1-piperazinecarboxylate (0.482 g, 1.27 mmol) was dissolved in 20 mL of DCM with stirring. TFA (4.0 mL, 52 mmol) was added, and the reaction was stirred for 4 h. The reaction was cooled to 0° C. and slowly quenched with 40 mL of 3N NaOH (aq.). The mixture was poured into H2O and DCM, and the layers were separated. The aqueous layer was washed with DCM. The combined organic layers were dried over MgSO4, filtered, and concentrated in vacuo to afford the title compound of step E (0.356 g, 1.27 mmol, 100%). 1H NMR (400 MHz, DMSO-d6) δ 7.86 (d, J=9.5 Hz, 1H), 6.57 (dd, J=9.5, 2.6 Hz, 1H), 6.46 (d, J=2.6 Hz, 1H), 3.88 (s, 3H), 3.77-3.86 (m, 2H), 2.93-3.02 (m, 1H), 2.82 (td, J=11.9, 3.3 Hz, 1H), 2.54-2.71 (m, 2H), 2.29-2.39 (m, 1H), 2.22 (br. s., 1H), 1.55-1.67 (m, 1H), 0.94 (d, J=6.8 Hz, 3H), 0.92 (d, J=6.8 Hz, 3H).
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