A stirring solution of (1R,2S,5R)-tert-butyl 2-((S)-3-(benzyloxycarbonylamino)-2-oxopyrrolidin-1-yl)-7-oxo-6-azabicyclo[3.2.1]octane-6-carboxylate (108 g, 0.236 mol) in THF (1 L) was charged with lithium hydroxide monohydrate (21.74 g, 0.519 mol). Water (0.3 L) was added slowly, such that the temperature did not exceed 20° C. The reaction was stirred at room temperature overnight and the volatiles were removed in vacuo. The pH was adjusted to ˜4 through the addition of 1N HCl (450 mL) and NaH2PO4. The resultant white precipitates were collected by filtration and washed with water (2×1 L). The solid was dissolved in dichloromethane (1.5 L) and water (˜1 L). The organic layer was dried (Na2SO4), filtered, and concentrated in vacuo. The residue was dissolved in EtOAc (0.7 L) and the resultant solution was heated at reflux for 1 h. Solids separated after cooling to RT, and were collected via filtration. These solids were purified by recrystallization in isopropanol to afford the desired (1R,2S,5R)-2-((S)-3-(benzyloxycarbonylamino)-2-oxopyrrolidin-1-yl)-5-(tert-butoxycarbonylamino)cyclohexanecarboxylic acid as a white solid (104.5 g, 93% yield). LC/MS for primary peak: [M-tBu+H]+=420.2; [M-Boc+H]+=376.2; [M+H]+=476.2. 1H-NMR (400 MHz, d4-MeOH): δ 7.35 (m, 5H), 5.11 (s, 2H), 4.35 (m, 2H), 3.71 (m, 1H), 3.45-3.6 (m, 2H), 2.99 (m, 1H), 2.41 (m, 1H), 2.15 (m, 1H), 2.0 (m, 2H), 1.6-1.9 (m, 4H), 1.46 (s, 9H).
