The methylation of 6-chloro-1H-indole-2-carboxylic acid ethyl ester (I) with NaH and Me-I in DMF gives the 1-methylindole derivative (II), which is condensed with 2-chloro-2-oxoacetic acid ethyl ester (III) by means of TiCl4 in dichloroethane to yield 6-chloro-2-[2-(ethoxycarbonyl)-1-methyl-1H-indol-3-yl]-2-oxoacetic acid ethyl ester (IV). The cyclization of (IV) with phenylhydrazine (V) in refluxing acetic acid affords the 7-chloro-5-methyl-4-oxo-3-phenyl-4,5-dihydro-3H-pyridazino[4,5-b]indole-1-carboxylic acid ethyl ester (VI). The reduction of the ester group of (VI) by means of NaBH4 in refluxing THF/methanol affords the hydroxymethyl derivative (VII), which is oxidized with MnO2 in refluxing dichloromethane to provide the corresponding carbaldehyde (VIII). The reaction of (VIII) with p-Toluenesulfonylmethyl isocyanide (TosMIC) and potassium tert-butoxide in dimethoxyethane gives the acetonitrile derivative (IX), which is hydrolyzed with HCl in refluxing methanol to yield the acetate ester derivative (X). Finally, this compound is treated with dimethylamine and trimethylaluminum in toluene to afford the target dimethylacetamide derivative.

The pyrazoledicarboxylic acid mono-methyl ester (I) was converted to the methyl benzyl diester (II) by treatment with benzyl bromide in the presence of DBU. Selective hydrolysis of the methyl ester function with KOH then provided the carboxylic acid (III). Coupling of acid (III) with deformyl distamycin A (IV) using EDC and HOBt gave amide (V). The protecting benzyl ester group of (V) was cleaved by catalytic hydrogenation over Pd/C to yield acid (VI). Amine (VIII) was obtained by acid cleavage of the Boc group from the protected precursor (VII). Subsequent coupling of amine (VIII) with carboxylic acid (VI) furnished the title compound.