The current study reports the synthesis of different derivatives of benzoselenophene analogs as well as a diverse series of compounds (14a–p, 15 and 16) from 1,2,9,9a-tetrahydrocyclopropa[c]benzo[e]indol-4-one (CBI) and benzoselenophene or heteroaromatic acids. The overall yield of scaffold 12 was improved by an one-pot reaction, which helps in large-scale synthesis of CBI, a duocarmycin alkylation subunit analog. The series of compounds were evaluated for their cytotoxicity against SK-OV3 ovarian cancer cell lines, which revealed that benzoselenophene can enhance or maintain the anticancer activity of the duocarmycin analog upon replacing the indole moiety. CBI-benzoselenophenes with N-amido substituents at the C-5 position, 14g, 14f and 16 (IC₅₀ = 0.5, 1.2 and 1.6 nM, respectively), were found to be more potent than the CBI-TMI and other benzoselenophene analogs. The CBI-benzoselenophene analogs, 14f and 14g (containing N-acetamido and N-butyramido substituents, respectively), were found to be 8 and 120 times more potent than the corresponding indole analogs of CBI, 14q and 14r, respectively.