[CH2:1]1[C:4]2([CH2:8][N:7]([C:9]([O:11][CH2:12][C:13]3[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=3)=[O:10])[CH2:6][CH2:5]2)[CH2:3][NH:2]1.C(N(CC)CC)C.[CH:26]([S:29](Cl)(=[O:31])=[O:30])([CH3:28])[CH3:27]>C(Cl)Cl>[CH:26]([S:29]([N:2]1[CH2:3][C:4]2([CH2:5][CH2:6][N:7]([C:9]([O:11][CH2:12][C:13]3[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=3)=[O:10])[CH2:8]2)[CH2:1]1)(=[O:31])=[O:30])([CH3:28])[CH3:27]A solution of benzyl 2,7-diazaspiro[3.4]octane-7-carboxylate (192 mg, 0.68 mmol) in DCM (1 mL) was treated with triethylamine (137 mg, 189 μL, 1.36 mmol) and isopropylsulfonyl chloride (107 mg, 84 μL, 0.75 mmol) at 0° C. The reaction mixture was stirred for 20 minutes. The reaction mixture was diluted with DCM and washed with 1N HCl and brine. The organic layer was dried over Na2SO4 filtered and concentrated under reduced pressure to obtain benzyl 2-isopropylsulfonyl-2,6-diazaspiro[3.4]octane-6-carboxylate (230 mg, 96%) as a colorless oil.
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