The synthesis of 10-formyl-5,8,10-trideazafolic acid ( 3) as a potential inhibitor of glycinamide ribonucleotide transformylase (GAR Tfase) is reported. The target compound was prepared by a convergent synthesis utilizing the alkylation of hydrazone 5 with benzylic bromide 6 to construct the core heterocycle 7. The aldehyde 3 and related agents were evaluated as inhibitors of purN GAR Tfase and avian AICAR Tfase. Compound 3 exhibited potent inhibition of GAR Tfase with a K i of 0.26 ± 0.05 μM. In contrast, 3 exhibited more moderate inhibition of aminoimidazole carboxamide ribonucleotide transformylase (AICAR Tfase), with K i of 7.6 ± 1.5 μM.