Trifluoromethanesulfonic anhydride → 4-nitrobenzyl (5R,6S)-3-[(2S,4S)-1-(4-nitrobenzyloxycarbonyl)-2-(pyridin-4-ylthiomethyl)pyrrolidin-4-ylthio]-6-[(1R)-1-(4-nitrobenzyloxycarbonyloxy)ethyl]-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate

Participants

Reaction Steps

To a solution of 4-nitrobenzyl (2R,5R,6S)-6-[(1R)-1-(4-nitrobenzyloxycarbonyloxy)ethyl]-3,7-dioxo-1-azabicyclo[3.2.0]heptane-2-carboxylate (1.2 g) in dry dichloromethane (40 ml) were added N,N-diisopropyl-N-ethylamine (0.44 ml) and trifluoromethanesulfonic anhydride (0.40 ml) at -40° C., and the solution was stirred at the same temperature for 15 minutes. To this solution were added N,N-diisopropyl-N-ethylamine (0.63 ml) and a solution of (2S,4S)-4-mercapto-1-(4-nitrobenzyloxycarbonyl)-2-(pyridin-4-ylthiomethyl)pyrrolidine (1.38 g) in dry dichloromethane (5 ml) successively at the same temperature under an atmosphere of nitrogen, and stirred at ambient temperature for 2 hours. The reaction mixture was washed with saturated aqueous sodium chloride, dried over anhydrous magnesium sulfate and evaporated in vacuo to give a residue. The residue was chromatographed on silica gel (100 g) eluting with a mixture of dichloromethane and acetone (4:1 V/V). The fractions containing the desired compound were collected and evaporated in vacuo to give 4-nitrobenzyl (5R,6S)-3-[(2S,4S)-1-(4-nitrobenzyloxycarbonyl)-2-(pyridin-4-ylthiomethyl)pyrrolidin-4-ylthio]-6-[(1R)-1-(4-nitrobenzyloxycarbonyloxy)ethyl]-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate (0.94 g).

Provenance & Evidence