(5R,6S)-6-((R)-1-Hydroxy-ethyl)-3-[4-(4-nitro-benzyloxycarbonylamino)-butylsulfanyl]-7-oxo-4-thia-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester

(5S,6S)-6-((R)-1-Hydroxy-ethyl)-3-[4-(4-nitro-benzyloxycarbonylamino)-butylsulfanyl]-7-oxo-4-thia-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester

{(2R,3S)-3-[(R)-1-(tert-Butyl-dimethyl-silanyloxy)-ethyl]-2-[4-(4-nitro-benzyloxycarbonylamino)-butylsulfanylthiocarbonylsulfanyl]-4-oxo-azetidin-1-yl}-(triphenyl-λ5-phosphanylidene)-acetic acid 4-nitro-benzyl ester

(5R,6S)-3-(3-Azido-propylsulfanyl)-6-((R)-1-hydroxy-ethyl)-7-oxo-4-thia-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester

p-nitrobenzyl 2-<(3S,4R)-3-<(1R)-(tert-butyldimethylsiloxy)ethyl>-4-(4-p-nitrobenzyloxycarbonylaminobutyrylthio)-2-oxoazetidin-1-yl>-2-hydroxyacetate