反应详情

A solution of N,N-diisopropyl-N-ethylamine (0.135 ml) in methylene chloride (1.21 ml) was added to a solution of 4-nitrobenzyl (2R, 5R, 6R)-3,7-dioxo-6-[1-methyl-1-(4-nitrobenzyloxycarbonyloxy)ethyl]-1-azabicyclo[3.2.0]heptane-2-carboxylate (350 mg) and 4-(N,N-dimethylamino)pyridine (7.9 mg) in methylene chloride (17.5 ml) at -30° C. A solution of trifluoromethanesulfonic anhydride (0.114 ml) in methylene chloride (1.02 ml) was added to the mixture and stirring was continued at the same temperature for 30 minutes. A solution of N,N-diisopropyl-N-ethylamine (0.563 ml) in methylene chloride (5.06 ml) and 5-methyl-1,3,4-oxadiazole-2-thiol (225 mg) were then added thereto, and the reaction mixture was stirred at -30° C. for 30 minutes and allowed to warm to ambient temperature over a period of an hour. After stirring at ambient temperature for 4 hours, the mixture was allowed to stand at 5° C. for 14 hours. After the solvent was removed by evaporation, the residue was dissolved in ethyl acetate (20 ml). The organic solution was washed in turn with water and a saturated aqueous sodium chloride, dried over magnesium sulfate and evaporated in vacuo. The residue was chromatographed on deactivated silica gel with 10% water (7 g), eluting with a mixture of benzene and acetone (20:1 to 10:1) to give 4-nitrobenzyl (5R, 6R)-6-[1-methyl-1-(4-nitrobenzyloxycarbonyloxy)ethyl]-3-(5-methyl-1,3,4-oxadiazol-2-ylthio)-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate (290 mg) as an oil.

1. stirringthe reaction mixture was stirred at -30° C. for 30 minutes
2. stirringAfter stirring at ambient temperature for 4 hours
3. waitto stand at 5° C. for 14 hours
4. customAfter the solvent was removed by evaporation
5. dissolutionthe residue was dissolved in ethyl acetate (20 ml)
6. washThe organic solution was washed in turn with water
7. dry with materiala saturated aqueous sodium chloride, dried over magnesium sulfate
8. customevaporated in vacuo
9. customThe residue was chromatographed on deactivated silica gel with 10% water (7 g)
10. washeluting with a mixture of benzene and acetone (20:1 to 10:1)