Doripenem Impurity II (Doripenem Dimer Impurity B)

(2S,2’S,3R,3’R)-2,2′-((2R,3S,7R,8S)-2,7-dimethyl-5,10-dioxo-1,6-bis(((3S,5S)-5-((sulfamoylamino)methyl)pyrrolidin-3-yl)thio)-2,3,5,7,8,10-hexahydrodipyrrolo[1,2-a:1′,2′-d]pyrazine-3,8-diyl)bis(3-hydroxybutanoic acid)