Treatment of 2-acetylfuran 6a with diethyl azodicarboxylate gave the cycloadduct 7, 6,7-diethoxycarbonyl-6,7-diaza-8-oxabicyclo[3.2.1]oct-3-en-2-one, whereas 5-methyl-2-formylfuran 6b reacted giving a simple hydrazide product derived from radical reaction on the formyl group. The structure of the bicyclic compound 7, established by NMR measurements, was confirmed by an X-ray crystallographic analysis. Variable temperature ¹H NMR and ¹³C NMR studies of 7 indicate that this compound undergoes two distinct dynamic conformational changes with ΔG ^‡ 10.2 and 13.1 kcal mol^–1 respectively. The reaction mechanism associated with the domino reaction between furfural 1 and dimethyl azodicarboxylate 9 to give the cycloadduct 10 has been theoretically characterized using ab initio methods at the RHF/6-31G* level. The reaction pathway can be described as a three-step process. The first step corresponds with a [4 + 2] cycloaddition between 1 and 9, while the two subsequent steps are associated with a structural isomerization of the initial formyl cycloadduct to a more stable final adduct.

A series of compounds containing the sulfonamide scaffold were synthesized and screened for their in vitro anticancer activity against a representative panel of human cancer cell lines, leading to the identification of N-(2-methyl-1H-indol-5-yl)-1-naphthalenesulfonamide (8e) as a compound showing a remarkable activity across the panel, with IC50 values in the nanomolar-to-low micromolar range. Cell cycle distribution analysis revealed that 8e promoted a severe G2/M arrest, which was followed by cellular senescence as indicated by the detection of senescence-associated β-galactosidase (SA-β-gal) in 8e-treated cells. Prolonged 8e treatment also led to the onset of apoptosis, in correlation with the detection of increased Caspase 3/7 activities. Despite increasing γ-H2A.X levels, a well-established readout for DNA double-strand breaks, in vitro DNA binding studies with 8e did not support interaction with DNA. In agreement with this, 8e failed to activate the cellular DNA damage checkpoint. Importantly, tubulin staining showed that 8e promoted a severe disorganization of microtubules and mitotic spindle formation was not detected in 8e-treated cells. Accordingly, 8e inhibited tubulin polymerization in vitro in a dose-dependent manner and was also able to robustly inhibit cancer cell motility. Docking analysis revealed a compatible interaction with the colchicine-binding site of tubulin. Remarkably, these cellular effects were reversible since disruption of treatment resulted in the reorganization of microtubules, cell cycle re-entry and loss of senescent markers. Collectively, our data suggest that this compound may be a promising new anticancer agent capable of both reducing cancer cell growth and motility.