Oxalic acid dihydrate → Benzyl (2S,5R)-5-((benzyloxy)amino)piperidine-2-carboxylate oxalate

Participants

Reaction Conditions

Reaction Steps

To a slurry of benzyl 5-[(benzyloxy)amino]piperidine-2-carboxylate ethanedioate (1:1) (10 g, 23.3 mmol, 3:1, SR:SS) in ethyl acetate (70 ml) was added a solution of potassium bicarbonate (9.3 g, 93 mmol, 4 eq) in water (90 ml). The mixture was stirred until all the solids had dissolved. The layers were separated and the aqueous layer was extracted with ethyl acetate (30 ml). The combined organic layers were washed with water (50 ml) and concentrated under vacuum below 40° C. to a final volume of 40 ml. The solution was passed through a filter and warmed to 45° C. Methanol (20 ml) at 40° C. was added, followed by a freshly prepared solution of oxalic acid dihydrate (3.67 g, 29.1 mmol) in methanol (10 ml). The mixture was cooled and the product was isolated by filtration. The solid was washed with an ethyl acetate/methanol mixture, then with ethyl acetate. The solid was dried to give benzyl (2S,5R)-5-[(benzyloxy)amino]piperidine-2-carboxylate ethanedioate (1:1) as a single isomer (7.0 g, 16.3 mmol, 70%).

Provenance & Evidence