Synonyms: 1H-Xantheno(2,1,9-def)isoquinoline-2(3H)-ethanesulfonic acid, 9-methoxy-1,3-dioxo-;9-Methoxy-1,3-dioxo-1H-xantheno(2,1,9-def)isoquinoline-2(3H)-ethanesulphonate acid;2-(9-methoxy-1,3-dioxo-1H-benzo[3,4]isochromeno[7,8,1-def]isoquinolin-2(3H)-yl)ethanesulfonic acid