Cefoperazone Dimer Impurity 61

2- ((R) -2- (4- (((R) -2- ((R) -carboxy ((R) -2- (4-ethyl-2,3-dioxopiperazine-1-carboxamido) -2- (4-hydroxyphenyl) acetamido) methyl) -5- (((1-methyl-1H-tetrazol-5-yl) thio) methyl) -3,6-dihydro-2H-1,3-thiazine-4-carbonyl) oxy) phenyl) -2- (4-ethyl-2,3-dioxopiperazine-1-carboxamido) acetamido) -2- (7-oxo-1,2,5,7-tetrahydro-4H-furo[3,4-d][1,3]thiazin-2-yl) acetic acid