Cefixime impurity 13/Cefixime TBE impurity A/Cefixime tert-Butyl Ester/(6R,7R)-7-((Z)-2-(2-aminothiazol-4-yl)-2-((2-(tert-butoxy)-2-oxoethoxy)imino)acetamido)-8-oxo-3-vinyl-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid [ 79368-92-6 ]