Synthesis and antitumoral evaluation of 3',4'-unsaturated nucleoside analogues bearing a chlorinated remdesivir-like base.

Nucleoside analogues are traditionally developed as antimetabolites that interfere with nucleic acid synthesis after intracellular phosphorylation. In this study, inspired by the 3',4'-unsaturated sugar scaffold of ddhCTP, we designed and synthesized a series of 3',4'-unsaturated nucleoside analogues to explore their antiproliferative potential and possible non-classical cellular effects. Among the synthesized compounds, 17k, a C-nucleoside bearing both a 3',4'-unsaturated sugar moiety and a chlorinated remdesivir-like base, exhibited potent antiproliferative activity against HepG2 cells, with an IC₅₀ value of 2.27 ± 0.36 μM, lower than that of gemcitabine under the same assay conditions. In the nonmalignant GES-1 epithelial cell line, 17k showed an IC₅₀ value of 34.26 ± 3.45 μM, corresponding to a selectivity index of 15.1 relative to HepG2 cells. Closely related compounds 12 and 17j showed no detectable activity, indicating a narrow structure-activity relationship. Exploratory single-concentration kinase profiling at 20 μM showed strong inhibition of several transcription-associated CDK/cyclin complexes (CDK13/CycK, CDK12/CycK, CDK9/CycT1, CDK19/CycC, and CDK8/CycC) and selected receptor tyrosine kinases (KDR/VEGFR2, RET, EPHA1, and FLT3). Compound 17k also suppressed colony formation and wound closure, induced apoptosis, and caused S-phase accumulation in HepG2 cells. These findings identify 17k as a nucleoside analogue with unanticipated antiproliferative activity and suggest that kinase modulation may contribute to its cellular effects.