In preceding studies,[1]we detailed the preparation and evaluation of potent inhibitors of glycinamide ribonucleotide transformylase (GAR Tfase) and aminoimidazole carboxamide ribonucleotide transformylase (AICAR Tfase), folate dependent enzymes responsible for the transfer of a formyl group to GAR and AICAR in the de novo synthesis of purines, based on the 5,8,10-trideazafolate core. The most effective of the agents incorporated a reactive, electrophilic group ...