Design, synthesis and biological activity of N-substituted tetrahydropteroate analogs as non-classical antifolates against cobalamin-dependent methionine synthase and potential anticancer agents.

Cobalamin-dependent methionine synthase (MetH) is involved in the process of tumor cell growth and survival. In this study, a novel series of N-electrophilic substituted tetrahydropteroate analogs without glutamate residue were designed as non-classical antifolates and evaluated for their inhibitory activities against MetH. In addition, the cytotoxicity of target compounds was evaluated in human tumor cell lines. With N-chloracetyl as the optimum group, further structure research on the benzene substituent and on the 2,4-diamino group was also performed. Compound 6c, with IC value of 12.1 μM against MetH and 0.16-6.12 μM against five cancer cells, acted as competitive inhibitor of MetH. Flow cytometry studies indicated that compound 6c arrested HL-60 cells in the G-phase and then inducted late apoptosis. The molecular docking further explained the structure-activity relationship.