Modified thymidine analogues have been highlighted as useful agents for the treatment of cancer and viral diseases due to their potent biological activities. In the present study, we synthesized a new thymidine analogue, 7-(3-bromo-phenoxy)-thymidine (4a), as a potential lead for anti-tumor agent. Compound 4a potently inhibits HeLa cell proliferation with an IC(50) of 15 microM.