5-Thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid,7-[[(2-ethoxyethoxy)phenylacetyl]amino]-7-methoxy-3-[[(1-methyl-1H-tetrazol-5-yl)thio]methyl]-8-oxo-, diphenylmethyl ester, (6R)-