1-pentanaminium, 5-[[3-[(acetyloxy)methyl]-2-carboxy-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-en-7-yl]amino]-1-carboxy-5-oxo-, inner salt, monosodium salt InChI=1/C16H21N3O8S.Na/c1-7(20)27-5-8-6-28-14-11(13(22)19(14)12(8)16(25)26)18-10(21)4-2-3-9(17)15(23)24;/h9,11,14H,2-6,17H2,1H3,(H,18,21)(H,23,24)(H,25,26);/q;+1/p- sodium 3-[(acetyloxy)methyl]-7-[(5-ammonio-5-carboxylatopentanoyl)amino]-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate