4-nitrobenzyl (4R,5R,6S)-6-[(1R)-1-hydroxyethyl]-4-methyl-3,7-dioxo-1-azabicyclo[3.2.0]-heptane-2-carboxylate

4-nitrobenzyl (1 R ,5 S ,6 S)-2-(2-diethylcarbamoylphenylthio)-1-methyl-6-[1(R)-hydroxyethyl]-1-carbapen-2-em-3-carboxylate

2-Azetidineacetic acid, 3-[1-[[(1,1-dimethylethyl)dimethylsilyl]oxy]ethyl]-α-methyl-4-oxo-, phenylmethyl ester, [2S-[2α(S*),3β(S*)]]-

(3S,4S)-4-((1R)-1-benzyloxycarbonylethyl)-1-(tert-butoxycarbonylmethyl)-3-((1R)-1-tert-butyldimethylsilyloxy)-2-azetidinone