5-Thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid,7-[(5-amino-5-carboxy-1-oxopentyl)amino]-7-methoxy-3-[[(1-methyl-1H-tetrazol-5-yl)thio]methyl]-8-oxo-,[6R-(6a,7a)]-