sodium [6R-[6alpha,7beta(R*)]]-3-(acetoxymethyl)-7-(hydroxyphenylacetamido)-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate;(6R,6β)-3-[(Acetyloxy)methyl]-7α-[[(R)-hydroxy(phenyl)acetyl]amino]-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid sodium salt