The reaction of N-benzoyl-N?N?di-n-propyl-DL-isoglutamine (I) with N-3-chloropropyl-N?2-hydroxyethylpiperazine (II) by means of sodium methoxide in DMSO at 105 C gives N-[3-(N-benzoyl-N?N?di-n-propyl-DL-isoglutaminyl)oxypropyl]-N?(2-hydroxyethyl)piperazine (III), which is then condensed with 1-(p-chlorobenzoyl)-5-methoxy-2-methylindole-3-acetic acid (IV) by means of dicyclohexylcarbodiimide and NaHCO3 in ethyl acetate, and treated finally with maleic acid (V)