Carzelesin (CAS NO.: 119813-10-4), with its systematic name of 2-Benzofurancarboxamide, N-(2-((1-(chloromethyl)-1,6-dihydro-8-methyl-5-(((phenylamino)carbonyl)oxy)benzo(1,2-b:4,3-b')dipyrrol-3(2H)-yl)carbonyl)-1H-indol-5-yl)-6-(diethylamino)-, (S)-, could be produced through many synthetic methods.

Following is one of the synthesis routes: (S)-N-[2-[1-(chloromethyl)-5-hydroxy-8-methyl-1,2,3,6-tetrahydrobenzo [1,2-b:4,3-b]dipyrrol-3-ylcarbonyl]-1H-indol-5-yl]-6-(diethylamino) benzofuran-2-carboxamide (I) is condensed with phenyl isocyanate (II) in the presence of triethylamine in THF to produce Carzelesin.