Aztreonam Impurity A Catalogue A242501 CAS 87500-74-1 M.W 453.44 M.F C13H19N5O9S2 Specifications FAQs (2S,3S)-2-((Z)-2-(2-aminothiazol-4-yl)-2-(((2-carboxypropan-2-yl)oxy)imino)acetamido)-3-(sulfoamino)butanoic acid