4-Benzyloxy-5-methoxy-2-nitrobenzoic acid (I) is treated with oxalyl chloride to provide the corresponding acid chloride (II), which is subsequently coupled with (S)-2-pyrrolidinemethanol (III) to give amide (IV). Hydrogenation of (IV) over Pd/C removes the benzyl protecting group and reduces the nitro substituent to the amino benzamide (V). Reaction of the aniline (V) with allyl chloroformate affords the carbamate (VI). The phenolic hydroxyl of (VI) is alkylated with trichloroethyl 6-bromohexanoate (VII) to yield (VIII). Dess-Martin oxidation of the primary alcohol group of (VIII) with concomitant intramolecular cyclization leads to the desired pyrrolobenodiazepine (X) together with the overoxidized dione (IX), which can be separated by column chromatography.

Cleavage of the trichloroethyl ester of (X) using Zn/HCO2H gives the carboxylic acid (XI). The N-Boc benzindole derivative (XII) is deprotected under acidic conditions to the amine (XIII), which is subsequently coupled with acid (XI) to yield the amide (XIV). Finally, palladium catalyzed cleavage of the N-Alloc group of (XIV) with concomitant dehydration leads to the desired compound.