(S)-2-[(2S,4S)-4-Mercapto-1-(4-nitro-benzyloxycarbonyl)-pyrrolidin-2-yl]-[1,3]thiazinane-4-carboxylic acid ethyl ester

(2S,4R)-2-((R)-4-Carbamoyl-thiazolidin-2-yl)-4-methanesulfonyloxy-pyrrolidine-1-carboxylic acid 4-nitro-benzyl ester

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

2-[(4R,2S)-4-(tert-butyldimethylsilanyloxy)-1-(p-nitrobenzyloxycarbonyl)pyrrolidin-2-yl]-[1,3]thiazinane-4(R)-carboxylic acid

2-[(4R,2S)-4-(tert-butyldimethylsilanyloxy)-1-(p-nitrobenzyloxycarbonyl)pyrrolidin-2-yl]-[1,3]thiazinane-4(R)-carboxylic acid ethyl ester