[N:1]1([C:7]([O:9][CH2:10][C:11]2[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=2)=[O:8])[CH2:6][CH2:5][NH:4][CH2:3][CH2:2]1.C(N(C(C)C)CC)(C)C.[N:26]([CH:29]([CH3:31])[CH3:30])=[C:27]=[O:28]>ClCCl.CCOC(C)=O>[CH:29]([NH:26][C:27]([N:4]1[CH2:5][CH2:6][N:1]([C:7]([O:9][CH2:10][C:11]2[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=2)=[O:8])[CH2:2][CH2:3]1)=[O:28])([CH3:31])[CH3:30]To a solution of benzyl piperazine-1-carboxylate (1, 5.0 g, 23 mmol) and diisopropylethylamine (5.86 g, 45.4 mmol) in dichloromethane (50 mL) was added 2-isocyanatopropane (4.83 g, 56.8 mmol) and the mixture was stirred overnight at room temperature. The mixture was diluted with EtOAc (300 mL), washed with water (100 mL), dried (Na2SO4), filtered, and concentrated. The residue was purified by silica gel chromatography eluting with to 0-20% CH2Cl2/92:7:1 CHCl3/MeOH/concentrated NH4OH in CH2Cl2 to afford the title compound (3.94 g, 57%) as a white solid: 1H NMR (300 MHz, CDCl3) δ 7.45-7.25 (m, 5H), 5.14 (s, 2H), 4.19 (d, J=6.7 Hz, 1H), 4.05-3.90 (m, 1H), 3.60-3.45 (m, 4H), 3.44-3.25 (m, 4H), 1.20-1.10 (m, 6H); Multimode MS m/z 306 [M+H]+.
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