F. kyselina (4S)-3-acetyl-2-{[(2R)-2-[[(4-ethyl-2,3-dioxopiperazin-1-yl)karbonyl]amino]-2-fenylacetamido](karboxy)methyl}-5,5-dimethylthiazolidin-4-karboxylová (acetylované peniciloové kyseliny piperacilinu).
F. kyselina (4S)-3-acetyl-2-{[(2R)-2-[[(4-ethyl-2,3-dioxopiperazin-1-yl)karbonyl]amino]-2-fenylacetamido](karboxy)methyl}-5,5-dimethylthiazolidin-4-karboxylová (acetylované peniciloové kyseliny piperacilinu).