[C:1]([O:5][C:6](=[O:16])[NH:7][C:8]1([C:11]2[O:12][CH:13]=[CH:14][CH:15]=2)[CH2:10][CH2:9]1)([CH3:4])([CH3:3])[CH3:2].[CH3:17][N:18](C=O)C>CC#N.C([O-])(O)=O.[Na+]>[C:1]([O:5][C:6](=[O:16])[NH:7][C:8]1([C:11]2[O:12][C:13]([C:17]#[N:18])=[CH:14][CH:15]=2)[CH2:9][CH2:10]1)([CH3:4])([CH3:2])[CH3:3](1-Furan-2-yl-cyclopropyl)-carbamic acid tert-butyl ester (765 mg, 3.43 mmol) was dissolved in MeCN (7.7 mL) and cooled to −40° C. in an acetone/dry ice bath. Chloroulfonyl isocyante (0.45 mL, 5.1 mmol) was added in one portion via syringe and the reaction was allowed to stir at a temperature between −40 and −30° C. for 45 min. Anhydrous DMF (1.2 mL) was then added and stirring continued at room temperature for 30 min. The reaction was diluted with saturated aqueous NaHCO3 (100 ml) and extracted with EtOAc (3×50 mL). The combined organic layers were concentrated to a red liquid and chromatographed (silica, 5→25% EtOAc/hexanes) to give 400 mg of the title compound as a white solid, m/z 234.35 [M-t-Bu+MeCN]+.
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