2-[(2R,3R)-1-(1-Benzyloxycarbonyl-2-methyl-propenyl)-3-(1,3-dioxo-1,3-dihydro-isoindol-2-yl)-4-oxo-azetidin-2-ylsulfanyl]-malonic acid bis-(4-nitro-benzyl) ester

2-[(2R,3S)-1-(1-Benzyloxycarbonyl-2-methyl-propenyl)-3-(1,3-dioxo-1,3-dihydro-isoindol-2-yl)-4-oxo-azetidin-2-ylsulfanyl]-malonic acid bis-(4-nitro-benzyl) ester

benzyl (2S)-2-[(3S,4R)-4-chloro-3-phthalimido-2-oxazetidin-1-yl]-2-(1-chlorothio-1-methylethyl)-acetate

benzyl (2S,5R,6S)-3,3-dimethyl-7-oxo-6-phthalisoimido-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate

6-aminopenicillanic acid benzyl ester