Novel Ethyl 2-Aminopyrano[3,2-c]isochromene-3-carboxylate Derivatives: Synthesis, Spectral Characterization, and...

Cancer remains one of the most challenging threats to human health and has prompted intensive research in anticancer drug discovery and synthesis. Isocoumarins are natural lactones with several pharmacological activities, including cytotoxic and anticancer effects.

This study aimed to synthesize novel ethyl 2-aminopyrano[3,2-c]isochromene-3-carboxylate derivatives and evaluate their cytotoxicity against the MCF-7 breast cancer and A549 lung cancer cell lines, in comparison with a normal cell line (MCF-10A human breast cells).

First, 4-hydroxyisocoumarin was prepared. A series of ethyl 2-aminopyrano[3,2-c]isochromene-3-carboxylate derivatives was then synthesized via a one-pot, three-component reaction of 4-hydroxyisocoumarin, ethyl cyanoacetate, and aromatic aldehydes in ethanol under reflux in the presence of triethylamine. The resulting compounds were characterized using standard spectroscopic techniques, including IR, ¹H NMR, and ¹³C NMR, as well as elemental analyses. Finally, the cytotoxicity of the synthesized compounds was evaluated in MCF-7, A549, and MCF-10A cell lines using a colorimetric MTT assay.

The compounds were successfully synthesized, and the cytotoxicity assay demonstrated dose-dependent cytotoxic effects in the tested cell lines. Most compounds exhibited moderate or low toxicity, whereas some were non-toxic in these cells. The most cytotoxic compounds were 4g, 4n, and 4m, with IC₅₀ values of 120.77 ± 7.64, 141.43 ± 13.81, and 168.62 ± 3.59 μg/mL against MCF-7 cells, respectively, and 4a, with an IC₅₀ value of approximately 131.12 ± 11.00 μg/mL against A549 cells. Compared with MCF-10A non-cancerous cells, these compounds showed selectivity indices (SIs) of 4.14, 1.64, 2.47, and 3.42, respectively.

The compounds were synthesized in high yields and exhibited moderate-to-mild toxicity toward MCF-7, A549, and MCF-10A cells. Notably, halogen substitution at the ortho position of the phenyl ring increased toxicity, particularly in the MCF-7 cell line. However, the lack of selectivity observed for most compounds indicates that further structural refinement is required before this scaffold can be considered a viable anticancer lead.