(2S,4S)-4-Acetylsulfanyl-2-(2-methyl-isoxazolidin-5-yl)-pyrrolidine-1-carboxylic acid 4-nitro-benzyl ester

(4R,5S,6S)-3-[(3S,5S)-5-(3-Ethoxycarbonyl-4,5-dihydro-isoxazol-5-yl)-1-(4-nitro-benzyloxycarbonyl)-pyrrolidin-3-ylsulfanyl]-6-((R)-1-hydroxy-ethyl)-4-methyl-7-oxo-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester