The molecule is the mono-anion resulting from the removal of a proton from one of the carboxyic acid groups of ertapenem. It is a conjugate base of an ertapenem.
(4R,5S,6S)-3-[(3S,5S)-5-[(3-carboxylatophenyl)carbamoyl]pyrrolidin-1-ium-3-yl]sulfanyl-6-[(1R)-1-hydroxyethyl]-4-methyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate