The molecule is the anion of cephapirin obtained by removal of a proton form the carboxylic acid group. It is a conjugate base of a cephapirin.
(6R,7R)-3-(acetyloxymethyl)-8-oxo-7-[(2-pyridin-4-ylsulfanylacetyl)amino]-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate