Treatment of rebeccamycin (I) with 2-(diethylamino)ethyl chloride (II) and NaH in DMF at r.t. gave 8-N-(2-diethylaminoethyl)- rebeccamycin (III) (1). The target phosphate salt was then prepared by addition of H3PO4 to a suspension of (III) in water until a pH of 3-4.