1,1'-Carbonyldiimidazole → tert-butyl (3S,5R)-3-{[(benzyloxy)carbonyl]amino}-5-(3-ethoxy-3-oxopropanoyl)piperidine-1-carboxylate

Participants

Reaction Steps

To a solution of (3R,5S)-5-{[(benzyloxy)carbonyl]amino}-1-(tert-butoxycarbonyl)piperidine-3-carboxylic acid (2.25 g) in THF (60 ml) was added 1,1′-carbonylbis(1H-imidazole) (1.20 g) and the mixture was stirred at room temperature for 2 hr. (3-Ethoxy-3-oxopropanoyl)potassium (1.26 g) and magnesium chloride (700 mg) were added and the reaction mixture was stirred with heating to reflux for 4 hr. After cooling to room temperature, the reaction mixture was diluted with 1 M hydrochloric acid, and the mixture was extracted with ethyl acetate. The extract was washed successively with 3.5 M aqueous potassium carbonate solution and saturated brine and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure. The residue was subjected to silica gel column chromatography, eluted with ethyl acetate-hexane (10:90-80:20) and concentrated under reduced pressure to give the object compound (460 mg).

Provenance & Evidence