One-Pot Gateway to Quinazoline–Thiohydantoin Fused Scaffolds and Discovery of Their Antileukemic Activity

In drug discovery, fusing bioactive heterocyclic frameworks leads to new analogs with improved properties. Quinazoline and thiohydantoin are prominent heterocycles, recognized for their diverse pharmacological profiles. Although quinazolines fused with various heterocycles are present in numerous clinical drugs, quinazoline-thiohydantoin fused frameworks, along with their synthetic approaches, remain unreported. Here, we introduce a transition metal-free, one-pot approach that enables the efficient and high-yielding synthesis (up to 92% yield) of this previously unexplored class of heterocyclic compounds. A streamlined three-step domino reaction, enabling the <i>formation of three C-N bonds in a single operation</i>, followed by dehydrogenation step, results in the desired quinazoline-thiohydantoin fused scaffolds, which exhibit potent and selective cytotoxicity against multidrug-resistant P-glycoprotein-overexpressing CEM/ADR5000 leukemia cells. The compounds, achieving IC₅₀ values as low as 0.13 ± 0.02 μM, are over 290-fold more active <i>in vitro</i> than the clinical standard doxorubicin (IC₅₀ = 38.17 ± 13.32 μM). Screening of 474 kinases, <i>in silico</i> docking (binding energy: -7.38 ± 0.02 kcal/mol; pKi: 3.9 ± 0.12 μM), and dose-kinetic assays identified MAPK14 (p38α) as a primary target (IC₅₀ = 131 nM), consistent with its role in oncogenic stress signaling. Additionally, these compounds reduce nuclear localization of myocardin-related transcription factor A (MRTF-A), a key driver of tumor resistance. This new study lays the groundwork for developing quinazoline-thiohydantoin-based drugs that can overcome multidrug-resistance mechanisms.