(5R)-6t-amino-3,3-dimethyl-1c-[(toluene-4-sulfonyloxy)-acetyl]-(5rH)-4-thia-1-aza-bicyclo[3.2.0]heptan-7-one

6α-phthalimido-penicillanic acid methoxymethyl ester

(2S,5R,6S)-6-(1,3-dihydro-1,3-dioxo-2H-isoindol-2-yl)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid methyl ester

6α-amino-penicillanic acid methoxymethyl ester