Synthesis of some substituted 6-phenyl purine analogues and their biological evaluation as cytotoxic agents

A series of 6-(4-substituted phenyl)-9-(tetrahydropyran-2-yl)purines 3–9, 6-(4-substituted phenyl)purines 10–16, 9-((4-substituted phenyl)sulfonyl)-6-(4-substituted phenyl)purines 17–32 were prepared and screened initially for their in vitro anticancer activity against selected human cancer cells (liver Huh7, colon HCT116, breast MCF7). 6-(4-Phenoxy-phenyl)purine analogues 9, 16, 30–32, had potent cytotoxic activities. The most active purine derivatives 5–9, 14, 16, 18, 28–32 were further screened for their cytotoxic activity in hepatocellular cancer cells. 6-(4-Phenoxyphenyl)-9-(tetrahydropyran-2-yl)-9H-purine (9) had better cytotoxic activity (IC50 5.4 μM) than the well-known nucleobase analogue 5-FU and known nucleoside drug fludarabine on Huh7 cells. The structure–activity relationship studies reported that the substitution at C-6 positions in purine nucleus with the 4-phenoxyphenyl group is responsible for the anti-cancer activity.