[OH:1][CH2:2][CH2:3][N:4]1[CH2:9][CH2:8][N:7]([C:10]([O:12][C:13]([CH3:16])([CH3:15])[CH3:14])=[O:11])[CH2:6][CH2:5]1.CCN(CC)CC.[CH3:24][S:25](Cl)(=[O:27])=[O:26]>ClCCl>[CH3:24][S:25]([O:1][CH2:2][CH2:3][N:4]1[CH2:9][CH2:8][N:7]([C:10]([O:12][C:13]([CH3:16])([CH3:15])[CH3:14])=[O:11])[CH2:6][CH2:5]1)(=[O:27])=[O:26]To a solution of tert-butyl 4-(2-hydroxyethyl)piperazine-1-carboxylate (1.7 g, 7.4 mmol) and Et3N (1.12 g, 11.1 mmol) in dichloromethane (20 mL) was added methanesulfonyl chloride (1 g, 8.87 mmol) at 0° C. The mixture was stirred at room temperature for 3 h. The mixture was washed with brine. The organic layer was concentrated in vacuo to give crude tert-butyl 4-(2-(methylsulfonyloxy)ethyl)piperazine-1-carboxylate (2.1 g, 94%). This was used in the next step without purification. 1H NMR (300 MHz, CDCl3): δ 4.38 (t, 2H, J=5.3 Hz), 3.49-3.44 (m, 4 h), 3.09 (s, 3H), 2.79 (t, 2H, J=5.1 Hz), 2.58 (t, 4 h, J=5.0 Hz), 1.49 (s, 9H). LCMS: No molecular ion observed for desired mass.
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