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

(4R,5S,6S)-3-[(3S,5S)-5-((R)-4-Carbamoyl-thiazolidin-2-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

(2S,4R)-2-[((R)-4-acetoxymethyl)thiazolidin-2-yl]-4-(tert-butyldimethylsilanyloxy)-1-(p-nitrobenzyloxycarbonyl)pyrrolidine

(2S,4R)-2-[((R)-4-acetoxymethyl)thiazolidin-2-yl]-4-methanesulfonyloxy-1-(p-nitrobenzyloxycarbonyl)pyrrolidine

(4R,2S)-4-(tert-butyldimethylsilanyloxy)-2-(3-methanesulfonylthiazolidin-2-yl)-1-(p-nitrobenzyloxycarbonyl)pyrrolidine