Diethyl Pyrocarbonate → tert-Butyl ((1R,2S)-2-{[(4aR*,5R*,10bR*)-5-phenyl-3,4,4a,5,6,10b-hexahydrobenzo[h]-1,6-naphthyridin-1(2H)-yl]carbonyl}cyclohexyl)carbamate

Participants

Reaction Steps

TFA (1 ml) was added to tert-butyl (4aR*,5R*,10bR*)-5-phenyl-3,4,4a,5,6,10b-hexahydrobenzo[h]-1,6-naphthyridine-1(2H)-carboxylate (195 mg, 0.54 mmol), and the mixture was stirred at room temperature for 3 min. Ice water was added to the reaction mixture, basified with 8N aqueous sodium hydroxide solution, and the mixture was extracted with ethyl acetate. The extract was washed with saturated brine, dried (over anhydrous MgSO4), and the solvent was evaporated under reduced pressure. The residue was dissolved in tetrahydrofuran (3 ml), (1S,2R)-2-[(tert-butoxycarbonyl)amino]cyclohexanecarboxylic acid (131 mg, 0.54 mmol) and triethylamine (109 mg, 1.1 mmol) were added, DEPC (88 mg, 0.54 mmol) was added at 0° C., and the mixture was stirred overnight at room temperature. Water was added to the reaction mixture and the mixture was extracted with ethyl acetate. The extract was washed with 6% aqueous sodium hydrogen carbonate solution and saturated brine, dried (over anhydrous MgSO4), and the solvent was evaporated under reduced pressure. The residue was subjected to column chromatography using silica gel (30 g), and eluted with hexane-ethyl acetate (9:1-4:1, v/v) to give the title compound (69 mg, 26%) as a colorless amorphous form.

Provenance & Evidence