3-picoline (52.6 ml, 543 mmol, 4 eq) was added to a slurry of ethyl (2S,5R)-5-[(benzyloxy)amino]piperidine-2-carboxylate ethanedioate (1:1) (50 g, 136 mmol, 1 eq) in dichloromethane (1000 ml) at 0° C., followed by a solution of triphosgene (36.4 g, 122.4 mmol, 0.9 eq) in dichloromethane (200 ml). The mixture was stirred at 0° C. until the reaction was deemed to be complete. The reaction was quenched with a solution of sodium bicarbonate (28.6 g, 340 mmol, 2.5 eq) in water (300 ml), and the layers were separated. The aqueous layer was extracted with dichloromethane (100 ml) and the combined organic layers were washed with water. The organic layer was concentrated in vacuo to give (2S,5R)-6-benzyloxy-7-oxo-1,6-diaza-bicyclo[3.2.1]octane-2-carboxylic acid ethyl ester as a solution in dichloromethane (solution yield: 35 g, 116 mmol, 85%). Acetonitrile was added and the solution was concentrated in vacuo to give (2S,5R)-6-benzyloxy-7-oxo-1,6-diaza-bicyclo[3.2.1]octane-2-carboxylic acid ethyl ester as a solution in acetonitrile. This solution was diluted with acetonitrile to 700 ml. To this was added ammonium carbamate (11.3 g, 145 mmol, 1.25 eq) and Novozyme 435 (35 g, immobilized Candida antarctica lipase B). The mixture was stirred at 40° C. until the reaction was deemed to be complete. The reaction mixture was filtered and concentrated in vacuo. The solution was diluted with dichloromethane, washed with aqueous ammonium chloride, and concentrated in vacuo. Chlorobutane was added and the solution was concentrated in vacuo. The precipitate was isolated by filtration, washed with chlorobutane and dried to give 2S,5R)-6-(benzyloxy)-7-oxo-1,6-diazabicyclo[3.2.1]octane-2-carboxamide as a white solid (24.3 g, 88 mmol, 65% from ethyl (2S,5R)-5-[(benzyloxy)amino]piperidine-2-carboxylate ethanedioate).
