Trifluoroacetic acid → tert-butyl (3R)-3-(aminooxy)pyrrolidine-1-carboxylate

To a mixture of tert-butyl (3S)-3-[({[(2S,5R)-7-oxo-6-(sulfooxy)-1,6-diazabicyclo[3.2.1]oct-2-yl]carbonyl}amino)oxy]pyrrolidine-1-carboxylate 10 (0.11 g, 0.24 mmol) in DCM (4.0 mL) was added trifluoroacetic acid (0.20 mL) at 0° C. The mixture was stirred at 0° C. for 1 h, concentrated and washed with ether. The white solid was collected by centrifugation. The crude product was purified by preparative HPLC to provide Compound 2 (Table 1)(30.4 mg, 36%) as a white solid.