(2S,4R)-2-[3-(2-chloroethanesulfonyl)thiazolidin-2-yl]-4-(tert-butyldimethylsilanyloxy)-1-(p-nitrobenzyloxycarbonyl)pyrrolidine

(2S,4S)-4-Mercapto-2-[3-(2-thiomorpholin-4-yl-ethanesulfonyl)-thiazolidin-2-yl]-pyrrolidine-1-carboxylic acid 4-nitro-benzyl ester

6-(1-hydroxy-ethyl)-4-methyl-3-(1-(4-nitro-benzyloxycarbonyl)-5-{3-[2-(4-pyrimidin-2-yl-piperazin-1-yl)-ethanesulfonyl]-thiazolidin-2-yl}-pyrrolidin-3-ylsulfanyl)-7-oxo-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester

(2S,4S)-4-Mercapto-2-{3-[2-(4-pyrimidin-2-yl-piperazin-1-yl)-ethanesulfonyl]-thiazolidin-2-yl}-pyrrolidine-1-carboxylic acid 4-nitro-benzyl ester