Synthesis of 2,3-dihydrobenzo[b][1,4]dioxine-5-carboxamide and 3-oxo-3,4-dihydrobenzo[b][1,4]oxazine-8-carboxamide derivatives as PARP1 inhibitors

Abstract Poly(ADP-ribose)polymerase 1 (PARP1), a widely explored anticancer drug target, plays an important role in single-strand DNA break repair processes. High-throughput virtual screening (HTVS) of the Maybridge small molecule library using the PARP1-benzimidazole-4-carboxamide crystal structure and pharmacophore model led to the identification of eleven compounds. These compounds were evaluated using recombinant PARP1 enzyme assay that resulted in the acquisition of three PARP1 inhibitors: 3 (IC50 = 12 μM), 4 (IC50 = 5.8 μM), and 10 (IC50 = 0.88 μM). Compound 4 (2,3-dihydro-1,4-benzodioxine-5-carboxamide) was selected as a lead and it was subjected to further chemical modifications, involving analogue synthesis and scaffold hopping. These efforts led to the identification of (Z)-2-(4-hydroxybenzylidene)-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-8-carboxamide (49, IC50 = 0.082 μM) as the most potent inhibitor of PARP1 from the series.