Treatment of 1,4-di(benzyloxy)-5,8-dichloro-9,10-dihydro-9,10-anthracenedione (I) with CuCN in hot DMA results in the desired monosubstituted derivative (II). Subsequent basic hydrolysis of the nitrile group of (II) leads to carboxylic acid (III). After conversion of (III) into the corresponding acid chloride (IV) by means of PCl5, reaction with 2-(dimethylamino)ethylhydrazine (V) produces the tetracyclic compound (VI). Displacement of the remaining chloride of (VI) with 2-(dimethylamino)ethylamine (VII) in DMA then gives (VIII). The protecting benzyl groups of (VIII) are finally removed with trifluoroacetic acid to furnish the title compound.