Methyl chloroformate → 1-benzyl 5-tert-butyl (1S)-{1-[(5-amino-1-methyl-1H-pyrazol-4-yl)carbamoyl]pentamethylene}biscarbamate

Participants

Reaction Steps

To a solution of (2S)-2-[(benzyloxycarbonyl)amino]-6-[(tert-butoxycarbonyl)amino]hexanoic acid (19.02 g) and triethylamine (5.56 g) in tetrahydrofuran (200 ml) was added methyl chloroformate (4.21 ml), followed by stirring under ice-cooling for 30 minutes. To the reaction mixture was added a solution of 1-methyl-1H-pyrazole-4,5-diamine sulfate (15.75 g) and triethylamine (15.2 g) in water (50 ml) at the same temperature. The mixture was stirred at room temperature for 30 minutes. To the reaction mixture was added chloroform (300 ml), and the layers were separated. The organic layer was washed successively with 10% aqueous citric acid solution, brine and saturated aqueous sodium hydrogencarbonate solution. The organic layer was dried over anhydrous magnesium sulfate, filtered and concentrated in vacuo to give a crude product of 1-benzyl 5-tert-butyl (1S)-{1-[(5-amino-1-methyl-1H-pyrazol-4-yl)carbamoyl]pentamethylene}biscarbamate as an oil. The crude product was used directly in the next step without further purification.

Provenance & Evidence