Treatment of the cyclopropabenzindole derivative (CBI) (I) with hydrochloric acid in ethyl acetate affords the chloromethyl derivative (II). The final step is the condensation of (II) with the acid (VIII) by means of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI) in DMF. The acid (VIII) was prepared as follows: Ethyl 5-nitroindole-2-carboxylate (III) is reductively transformed to its corresponding amine (IV) by hydrogenation over Pd/C. The amine (IV) is then converted to its acetamido ester (V) by treatment with acetic anhydride in ethyl acetate. Ester (V) is then hydrolyzed using NaOH to afford the corresponding acid (VI), which is coupled to amine (IV) in the presence of EDCI to yield ester (VII). Finally (VII) is converted to acid (VIII) by treatment with NaOH.

Treatment of the cyclopropabenzindole derivative (CBI) (I) with hydrochloric acid in ethyl acetate affords the chloromethyl derivative (II). The final step is the condensation of (II) with the acid (VIII) by means of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI) in DMF. The acid (VIII) was prepared as follows: Ethyl 5-nitroindole-2-carboxylate (III) is reductively transformed to its corresponding amine (IV) by hydrogenation over Pd/C. The amine (IV) is then converted to its acetamido ester (V) by treatment with acetic anhydride in ethyl acetate. Ester (V) is then hydrolyzed using NaOH to afford the corresponding acid (VI), which is coupled to amine (IV) in the presence of EDCI to yield ester (VII). Finally (VII) is converted to acid (VIII) by treatment with NaOH.