(2S,5R,6S)-6-Bromo-6-[1-(tert-butyl-dimethyl-silanyloxy)-ethyl]-3,3-dimethyl-7-oxo-4-thia-1-aza-bicyclo[3.2.0]heptane-2-carboxylic acid methyl ester

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

4-乙酰氧基氮杂环丁酮

dl-p-nitrobenzyl 2-<(3R*,4S*)-3-<(1R*)-(tert-butyldimethylsiloxy)ethyl>-4-(5-p-nitrobenzyloxycarbonylaminopentanoylthio)-2-oxoazetidin-1-yl>-2-hydroxyacetate