2-ethyl-5,7,12-trihydroxy-6,11-dioxo-1-{[2,3,6-trideoxy-3-(dimethylamino)hexopyranosyl]oxy}-1,2,3,4,6,11-hexahydrotetracen-2-yl 2,3,6-trideoxy-3-(dimethylamino)hexopyranoside