Which of the following antitumor agents works by impairing de novo purine synthesis?

Among the given antitumor drugs, methotrexate which is folic acid analog act as a folate antagonist that inhibit the conversion of (DHFA)Dihydro folic acid to tetra hydrofolic acid (THFA). We know that follic acid is utilized in de novo synthesis. Where as 5-fluorouracil act as pyrimidine antagonist by inhibiting the conversion of deoxyuridine acid to deoxythymidylic acid. And Allopurinol act by inhibiting uric acid synthesis. ESSENTIALS OF MEDICAL PHARMACOLOGY-SEVENTH EDITION -K.D TRIPATHI Page:864,862,216