Pixantrone Maleate Impurity 11

Tert-butyl (2- ((6- ((2-aminoethyl) amino) -5,10-dioxo-5,10-dihydrobenzo[g]isoquinolin-9-yl) amino) ethyl) carbamate--tert-butyl (2- ((9- ((2-aminoethyl) amino) -5,10-dioxo-5,10-dihydrobenzo[g]isoquinolin-6-yl) amino) ethyl) carbamate (1/1)