6-Nitroindole (I) was methylated using iodomethane and NaH and the resulting 1-methyl-6-nitroindole (II) was acylated with oxalyl chloride in dichloromethane to furnish the glyoxylyl chloride (III). Subsequent condensation of (III) with 1-methylindole-3-acetic acid (IV) in the presence of Et3N gave the bisindolylmaleic anhydride (V). This was finally converted into the target maleimide by heating with ammonia in aqueous DMF in a sealed vessel at 140 C.