Two new dichlorophenylfurylnicotinamidine regioisomers and were prepared from the corresponding dichlorophenylfurylnicotinonitriles when treated with lithium bis(trimethylsilyl)amide and subsequent deprotection, then hydrogen chloride salt formation. Nicotinonitriles were prepared employing a Suzuki coupling conditions for 6-(5-bromofuran-2-yl)nicotinonitrile with dichlorophenylboronic acids. Computational assessments provided insights into electronic structure and chemical reactivity. Their antiproliferative activities against 60 cancer cell lines spanning 9 tissue types were evaluated. 6-[5-(2,4-Dichlorophenyl)furan-2-yl]nicotinamidine dihydrochloride exhibited the highest overall potency with median GI(50) of 1.65 mu M. Molecular modeling showed the smallest HOMO-LUMO gap for analogue 6-[5-(3,4-dichlorophenyl)furan-2-yl]nicotinamidine dihydrochloride (1.91 eV), followed by 6-[5-(2,4-dichlorophenyl)furan-2-yl]nicotinamidine dihydrochloride (1.92 eV), relative to the lead 3,5-dichloro compound I (2.62 eV), suggesting 6-[5-(3,4-dichlorophenyl)furan-2-yl]nicotinamidine dihydrochloride has the highest chemical reactivity among the investigated amidines. Structure-activity analysis revealed the ability to modulate potency and toxicity through variations to the dichlorophenyl ring. The most responsive cell line was SR leukemia, with GI(50) values of 0.31 mu M and 0.55 mu M for 6-[5-(2,4-dichlorophenyl)furan-2-yl]nicotinamidine dihydrochloride and 6-[5-(3,4-dichlorophenyl)furan-2-yl]nicotinamidine dihydrochloride, respectively. We demonstrate the potential to rationally shift the therapeutic profile from overtly cytotoxic towards more cytostatic behavior through substituent changes to the terminal phenyl ring. Importantly, the synergistic integration of synthetic chemistry, biological screening, and computational analyses enabled key structure-activity relationships to be established, paving the way for further lead optimization efforts. Our interdisciplinary approach blending organic synthesis with high-throughput antiproliferative evaluation and quantum chemical modeling provides a framework amenable to systematic improvement of this novel chemotype. These initial promising findings warrant ongoing medicinal chemistry endeavors to identify clinical candidates boasting enhanced selectivity and wider therapeutic windows.
