(2S,4S)-2-{[2-(allyloxycarbonylamino)ethyl]carbamoyl}-4-tritylthio-1-(allyloxycarbonyl)pyrrolidine

(2S,4S)-4-Mercapto-2-(2-piperazin-1-yl-ethylcarbamoyl)-pyrrolidine-1-carboxylic acid allyl ester

(2S,4S)-4-Mercapto-2-(1-methanesulfonyl-4-methyl-4,5-dihydro-1H-imidazol-2-yl)-pyrrolidine-1-carboxylic acid allyl ester

(2R,4S)-2-(5-Carbamoyl-[1,2,4]oxadiazol-3-ylmethyl)-4-mercapto-pyrrolidine-1-carboxylic acid allyl ester

(2S,4S)-4-Mercapto-2-[2-(3-methyl-thioureido)-ethylcarbamoyl]-pyrrolidine-1-carboxylic acid allyl ester