[CH3:1][NH2:2].[CH2:3]([O:10][C:11]([N:13]1[CH2:17][CH2:16][CH:15]([S:18](Cl)(=[O:20])=[O:19])[CH2:14]1)=[O:12])[C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1.O>C1COCC1>[CH3:1][NH:2][S:18]([CH:15]1[CH2:16][CH2:17][N:13]([C:11]([O:10][CH2:3][C:4]2[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=2)=[O:12])[CH2:14]1)(=[O:20])=[O:19]Methylamine (40 wt % in H2O, 1 mL) was added to a solution of 3-chlorosulfonyl-pyrrolidine-1-carboxylic acid benzyl ester (256 mg, 0.843 mmol) in THF (1 mL) at 0° C. The mixture was stirred at 0° C. for 10 min, and then warmed to room temperature and stirred for 2 hrs. Water was added and the phases were separated. The aqueous phase was extracted with CH2Cl2 (2×), the combined organic extracts were dried (Na2SO4), and the solvent was removed under vacuum. Chromatography on neutral alumina, eluting with CH2Cl2/MeOH (99:1 to 95:5), gave benzyl 3-[(methylamino)sulfonyl]-1-pyrrolidinecarboxylate (173 mg, 69%): 1H NMR (CDCl3) δ 7.36-7.29 (m, 5H), 5.14 (d, J=1.9 Hz, 2H), 4.27 (d, J=42.6 Hz, 1H), 3.80-3.70 (m, 4H), 3.50 (m, 1H), 2.82 (d, J=4.9 Hz, 3H), 2.35 (m, 2H).
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