Under a nitrogen atmosphere, combine methyl-triphenylphosphonium bromide (67.4 g, 184.9 mmol) and tetrahydrofuran (300 mL) with agitation. Add a solution of potassium tert-butoxide (1M) in tetrahydrofuran, 184.9 mL, 184.9 mmol) to the reaction mixture over 15 minutes and stir the resulting slurry at ambient temperature for 3 hours. Dissolve diethyl (1S,2S,5R,6R)-2-benzyloxycarbonylamino-4-oxo-bicyclo[3.1.0]hexane-2,6-dicarboxylate (12.3 kg, 31.6 mol) in tetrahydrofuran (120 mL) and add to the reaction mixture over 1 hour, maintaining the reaction temperature below 30° C. Stir the resulting slurry overnight at ambient temperature, then dilute with ethyl acetate (600 mL) and quench with water (300 mL). After stirring the biphasic mixture for 30 minutes, separate the layers and wash the organics with water (300 mL) followed by 0.25M HCl (300 mL). Dry the organics over Na2SO4, filter, and concentrate in vacuo (45° C.) to afford the crude product as a dark oil (111.0 g). Purify the material by silica gel plug chromatography (1 Kg Kieselgel-60, 4 L 15% EtOAc in heptanes, then 10 L 30% EtOAc in heptanes) to afford the title compound as a clear oil (37.3 g, 87.9% potency, 54.9%). MS (m/z): 388 (M+1).
