Diphenyl chlorophosphate → 4-nitrobenzyl(5R,6S)-3-(4-pyridylthio)-6-[1-methyl-1-(4-nitrobenzyloxycarbonyloxy)ethyl]-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate

Participants

Reaction Conditions

Reaction Steps

To a solution of 4-nitrobenzyl(2R,5R,6S)-3,7-dioxo-6-[1-methyl-1-(4-nitrobenzyloxycarbonyloxy)ethyl]-1-azabicyclo[3.2.0]heptane-2-carboxylate (145.1 mg) and 4-(N,N-dimethylamino)pyridine (3.27 mg) in acetonitrile (7.3 ml) was added dropwise a solution of N,N-diisopropyl-N-ethylamine (56.0 μl) in acetonitrile (0.504 μl), followed by a solution of diphenyl-chlorophosphate (58.3 μl) in acetonitrile (0.525 ml) at 0° C. After stirring for an hour at 0° C., thereto was added a solution of N,N-diisopropyl-N-ethylamine (186.4 μl) in acetonitrile (1.68 ml), followed by 4-mercaptopyridine (31.3 mg) at -15° C. The mixture was allowed to stand overnight at -15° C. The resultant solution was diluted with ethyl acetate (15 ml) and then washed in turn with water and saturated aqueous sodium chloride. After drying over magnesium sulfate, the solution was filtered and evaporated in vacuo. The residue was chromatographed on silica gel (4 g) eluting with a mixture of benzene and acetone (30:1 to 6:1) to give 4-nitrobenzyl(5R,6S)-3-(4-pyridylthio)-6-[1-methyl-1-(4-nitrobenzyloxycarbonyloxy)ethyl]-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate (139.1 mg).

Provenance & Evidence