Propionic Acid → Ethyl (2S,5R)-5-((benzyloxy)amino)piperidine-2-carboxylate oxalate

Participants

Reaction Conditions

Reaction Steps

Propanoic acid (34.9 ml, 466.2 mmol, 6 eq) was added to a suspension of sodium borohydride (5.75 g, 155.4 mmol, 2 eq) in ethyl acetate (160 ml) and held until the reaction was deemed to be complete. The resulting solution was added to a solution of (S)-5-Benzyloxyimino-piperidine-2-carboxylic acid ethyl ester in ethyl acetate (120 ml total volume) and sulfuric acid (20.7 ml, 388.5 mmol, 5 eq) at −20° C. and held until reaction was deemed to be complete. The reaction was quenched by the addition of water (240 ml), then neutralized with aqueous ammonia solution. The organic layer was washed with water and concentrated in vacuo to 80 ml. The solution was warmed to 45° C. and held at this temperature. Ethanol (80 ml, 95%) at 40° C. was added, followed by a freshly prepared solution of oxalic acid dihydrate (9.8 g, 77.7 mmol) in ethanol (40 ml). The mixture was cooled and the product was isolated by filtration. The solid was washed with an ethyl acetate/ethanol mixture, then with ethyl acetate. The solid was dried to give ethyl (2S,5R)-5-[(benzyloxy)amino]piperidine-2-carboxylate ethanedioate (1:1) as a single isomer (16.4 g, 44.5 mmol, 57.3%).

Provenance & Evidence