[CH3:1][O:2][C:3]([C:5]1([NH:12][C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[CH2:7][CH:6]1[CH2:8][CH2:9]SC)=[O:4].O[O:21][S:22]([O-:24])=O.[K+].[CH3:26]O>O>[CH3:1][O:2][C:3]([C:5]1([NH:12][C:13]([O:15][C:16]([CH3:18])([CH3:17])[CH3:19])=[O:14])[CH2:7][CH:6]1[CH2:8][CH2:9][S:22]([CH3:26])(=[O:24])=[O:21])=[O:4]A solution of 1-tert-butoxycarbonylamino-2-(2-methylsulfanylethyl)-cyclopropanecarboxylic acid methyl ester (0.63 g, 2.2 mmol) in 10 mL MeOH was added slowly to a suspension of Oxone (2.0 g, 3.3 mmol) in 10 mL H2O at rt. After 2 h at rt, the solvent was removed in vacuo and the residue was taken up in EtOAc and H2O (15 mL each). The aqueous layer was extracted with 3×10 mL EtOAc. The combined organics were washed with brine and dried over anhydrous MgSO4. Following concentration in vacuo, the residue was purified by column chromatography on SiO2 (0→65% EtOAc/hexanes) to produce 1-tert-butoxycarbonylamino-2-(2-methanesulfonylethyl)-cyclopropanecarboxylic acid methyl ester (0.50 g, 71%) as a colorless film. LCMS found 222.0 [(M-Boc)+H]+.
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