(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)-

Participants

Reaction Steps

To a solution of 4-nitrobenzyl (4R)-2-diazo-4-[(2R,3S)-3-{(1R)-1-hydroxyethyl}-4-oxoazetidin-2-yl]-3-oxopentanoate (0.72 g) in 1,2-dichloroethane (15 ml) was added rhodium(II) acetate (2 mg) under reflux. The mixture was refluxed for 30 minutes under nitrogen atmosphere, cooled and then concentrated under reduced pressure 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 compound obtained above was dissolved in acetonitrile (15 ml) and N,N-diisopropyl-N-ethylamine (0.39 ml). Diphenyl phosphorochloridate (0.40 ml) was added thereto at -10°~-5° C. in a nitrogen stream, followed by stirring at -10°~-5° C. for 30 minutes. To the solution were added N,N-diisopropyl-Nethylamine (0.39 ml) and a solution of (2S,4S)-4-mercapto-1-(4-nitrobenzyloxycarbonyl)-2-[(2-ureidoethyl)oxymethyl]pyrrolidine (0.73 g) in acetonitrile (3 ml) at -20° C. successively. The mixture was stirred at the same temperature for 30 minutes and then at 0°-10° C. for 3 hours. The mixture was poured into ethyl acetate (150 ml) and water (100 ml). The organic layer was dried over magnesium sulfate and concentrated under reduced pressure to give a syrup. The syrup was subjected to a column chromatography on silica gel (20 g) eluting with a mixture of acetone and dichloromethane (1:1 V/V) to give 4-nitrobenzyl (4R,5S,6S)-6-[(1R)-1-hydroxyethyl]-4-methyl-3-[(2S,4S)-1-(4-nitrobenzyloxycarbonyl- 2-{(2-ureidoethyl)oxymethyl}pyrrolidin-4-yl]thio-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate (0.75 g).

Provenance & Evidence