acetylated penicilloic acids of piperacillin||Chemical Formula:C25H31N5O9S ||Molecular Weight:577.609 ||Exact Mass:577.18425 ||(4S)-3-acetyl-2-(carboxy((R)-2-(4-ethyl-2,3-dioxopiperazine-1-carboxamido)-2-phenylacetamido)methyl)-5,5-dimethylthiazolidine-4-carboxylic acid