(R)-4-Nitrobenzyl 2-diazo-4-((2R,3S)-3-((R)-1-hydroxyethyl)-4-oxoazetidin-2-yl)-3-oxopentanoate → 1-Azabicyclo[3.2.0]heptane-2-carboxylic acid, 6-[(1R)-1-hydroxyethyl]-4-methyl-3,7-dioxo-, (4-nitrophenyl)methyl ester, (4R,5R,6S)-

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Reaction Steps

To a solution of 4-nitrobenzyl (4R)-2diazo-4[(2R,3S)-3-{(1R)-1-hydroxyethyl}-4-oxoazetidin-2-yl]3-oxopentanoate (0.80g) in 1,2-dichloroethane (16 ml) was added rhodium(II) acetate (2 mg) under refluxing. After refluxing for 30 minutes, the reaction mixture was cooled and evaporated in vacuo to give a residue. The residue was dissolved in anhydrous acetonitrile (10 ml) and then evaporated. This operation was repeated once again and the residue was dried in vacuo to give 4-nitrobenzyl (4R,5R,6S)-6-[(1R)-1-hydroxyethyl]-4-methyl-3,7-dioxo-1-azabicyclo[3.2.0]heptane-2-carboxylate. The residue containing the compound obtained above was dissolved in anhydrous acetonitrile (16 ml) and cooled to 0° C. under an atmosphere of nitrogen. To this solution were added diphenyl phosphorochloridate (0.45 ml) and N,N-diisopropyl-N-ethylamine (0.46 ml) successively, and the solution was stirred at 0° C. for 40 minutes

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