2-(((Z)-(1-(2-((2S,3S)-2-((Z)-2-(2-Aminothiazol-4-yl)-2-(((2-carboxypropan-2-yl)oxy)imino)acetamido)-3-(sulfoamino)butanamido)thiazol-4-yl)-2-(((2S,3S)-2-methyl-4-oxo-1-sulfoazetidin-3-yl)amino)-2-oxoethylidene)amino)oxy)-2-methylpropanoic Acid is an Aztreonam (A965200) in-house impurity. Aztreonam is the first totally synthetic monocyclic β-lactam antibiotic.