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

(3S,4S)-3-<(R)-1-(t-butyldimethylsilyloxy)ethyl>-4-carbamoyl-2-azetidinone

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

Sodium; (5R,6S)-6-((R)-1-hydroxy-ethyl)-3-(3-hydroxy-propylsulfanyl)-7-oxo-4-thia-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylate

p-nitrobenzyl (5R,6S)-6-<(1R)-hydroxyethyl>-2-(2-p-nitrobenzyloxycarbonylaminoethyl)-2-penem-3-carboxylate