A stirring solution of 2-(trimethylsilyl)ethyl(1R,2S,5R)-2-((S)-3-benzyloxycarbonylamino-2-oxopyrrolidin-1-yl)-5-(cyanomethylamino)cyclohexylcarbamate (400 mg, 0.76 mmol) in dichloromethane (5 mL), was cooled to 0° C. and charged with m-CPBA (372.6 mg, 2.2 eq) in portions. The mixture was stirred at room temperature for 1.5 h. Saturated Na2S2O3 solution (3 mL) and saturated NaHCO3 solution (3 mL) were added and the mixture was stirred at room temperature for 0.5 h. The mixture was diluted with dichloromethane (80 mL), washed with saturated NaHCO3 (20 mL) and brine (20 mL). The solution was dried over anhydrous Na2SO4, filtered, and concentrated in vacuo. The residue obtained was dissolved in methanol (5 mL) and the solution was charged with NH2OH—HCl (262.7 mg, 5 eq). The mixture was stirred at 60° C. for 2.5 h. After cooling to room temperature, the mixture was diluted with dichloromethane (80 mL) and filtered through a pad of celite. The filtrate was washed with saturated NaHCO3 (2×20 mL). The aqueous washes were extracted with dichloromethane (30 mL). The dichloromethane layers were combined and washed with brine (30 mL). The solution was dried over anhydrous Na2SO4, filtered, and concentrated in vacuo to give 2-(trimethylsilyl)ethyl (1R,2S,5R)-2-((S)-3-benzyloxycarbonylamino-2-oxopyrrolidin-1-yl)-5-(hydroxyamino)cyclohexylcarbamate (350 mg, 91%). LC/MS found [M+H]+=507.
