[CH3:1][C@@H:2]1[CH2:7][N:6]([CH2:8][C:9]2[CH:14]=[CH:13][C:12]([N+:15]([O-])=O)=[CH:11][CH:10]=2)[CH2:5][C@H:4]([CH3:18])[N:3]1[C:19]([O:21][C:22]([CH3:25])([CH3:24])[CH3:23])=[O:20].[Cl-].[NH4+]>CO.O.[Fe]>[NH2:15][C:12]1[CH:13]=[CH:14][C:9]([CH2:8][N:6]2[CH2:5][C@H:4]([CH3:18])[N:3]([C:19]([O:21][C:22]([CH3:23])([CH3:25])[CH3:24])=[O:20])[C@H:2]([CH3:1])[CH2:7]2)=[CH:10][CH:11]=1
To a solution of 1,1-dimethylethyl (2R,6S)-2,6-dimethyl-4-[(4-nitrophenyl)methyl]-1-piperazinecarboxylate (D7) (2.62 g, 7.53 mmol) in MeOH (25 mL) and water (25 mL) heated to 80° C. was added iron powder (1.26 g, 22.54 mmol) and ammonium chloride (2.01 g, 37.58 mmol). The reaction was stirred vigorously at 80° C. for 1.5 h and then the iron residues removed by filtration through Celite®. The filtrate was concentrated and the residue partitioned between DCM and water. The aqueous layer was further extracted with DCM (×2) and the combined organics were dried and concentrated to give the crude product as a yellow foam (2.01 g). Column chromatography eluting with 0-100% Et2O/petroleum ether gave the title compound (1.694 g). δH (CDCl3, 400 MHz) 7.12 (2H, d), 6.64 (2H, d), 4.05 (2H, m), 3.64 (2H, br s), 3.36 (2H, s), 2.59 (2 h, d), 2.06 (2H, dd), 1.46 (9H, s), 1.27 (6H, d). MS (ES): MH+ 320.3, MNa+ 342.3.
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