(R)-2-[(2R,3R)-2-(Benzothiazol-2-yldisulfanyl)-3-(1,3-dioxo-1,3-dihydro-isoindol-2-yl)-4-oxo-azetidin-1-yl]-3-hydroxymethyl-but-3-enoic acid methyl ester

9-acetoxy-6β-phthalimido-penicillanic acid methyl ester

(6R)-3t-acetoxy-3c-methyl-8-oxo-7t-phthalimido-(6rH)-5-thia-1-aza-bicyclo[4.2.0]octane-2c-carboxylic acid methyl ester

10-acetoxy-6β-phthalimido-penicillanic acid methyl ester

2-[(2R,3R)-2-(Benzothiazol-2-yldisulfanyl)-1-(4-methyl-2-oxo-2,5-dihydro-furan-3-yl)-4-oxo-azetidin-3-yl]-isoindole-1,3-dione