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

(2R,4S)-2-{2-(3,3-Dimethyl-ureido)-2-[(Z)-hydroxyimino]-ethyl}-4-tritylsulfanyl-pyrrolidine-1-carboxylic acid allyl ester

(2R,4S)-2-{2-[3-(2-Hydroxy-ethyl)-ureido]-2-[(Z)-hydroxyimino]-ethyl}-4-tritylsulfanyl-pyrrolidine-1-carboxylic acid allyl ester

(2S,4S)-2-[(2-mesyloxyethyl)carbamoyl]-4-tritylthio-1-(allyloxycarbonyl)pyrrolidine

(2R,4S)-2-{2-[(Z)-Hydroxyimino]-2-methoxycarbonylamino-ethyl}-4-tritylsulfanyl-pyrrolidine-1-carboxylic acid allyl ester