Expeditious assembly of N-heteroaryl substituted quercetin derivatives as potent anticancer agents

Abstract

The synthesis of a small library of N-heteroaryl substituted quercetin derivatives (28 compounds) at the C8 position applying Suzuki-Miyaura cross-coupling reaction between 8-iodoquercetin methyl ether and various pyridylboronic acids or quinolylboronic acids is reported. The obtained quercetin derivatives 2a-2n and 3a-3n were well characterized by the 1H NMR, 13C NMR and HRMS data. Preliminary biological evaluations showed that some of the synthesized 8-heteroarylated quercetin derivatives possessed very high anti-cancer cell proliferation activity in HCC827 cancer cell line (IC50< 5.0 µmol/L) in vitro. Among these synthesized compounds, quinolin-7-yl substituted compound 2m exhibited best activity in HCC827 (IC50 = 3.20 µmol/L), while quinolin-3-yl substituted compound 2i showed best activity in MGC-803 cells (IC50 = 14.92 µmol/L). The 3-pyridyl compound 3c with ortho-fluorine showed best activity in OVCAR-3 cells (IC50 = 10.67 µmol/L). The disclosed structure-activity relationship provides hints that large steric hindrance at the C8 position of quercetin alter the anticancer activities and also offers new examples for new application of electronic and steric modifications as versatile tools in drug discovery.