Optimized 5-Membered Heterocycle-Linked Pterins for the Inhibition of Ricin Toxin A

The optimization of a series of pterin amides for use as Ricin Toxin A (RTA) inhibitors is reported. On the basis of crystallographic data of a previous furan-linked pterin, various expanded furans were synthesized, linked to the pterin, and tested for inhibition. Concurrently, heteroanalogues of furan were explored, leading to the discovery of more potent triazole-linked pterins. Additionally, we discuss a dramatic improvement in the synthesis of these pterin amides via a dual role by diazabicycloundecene (DBU). This synthetic enhancement facilitates rapid diversification of the previously challenging pterin heterocycle, potentially aiding future medicinal research involving this structure.