(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

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

(4R,5S,6S)-3-((3S,5S)-1-Allyloxycarbonyl-5-{[(thiomorpholine-4-carbonyl)-amino]-methyl}-pyrrolidin-3-ylsulfanyl)-6-((R)-1-hydroxy-ethyl)-4-methyl-7-oxo-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid allyl ester