Synthesis and In Vitro Studies of Novel Pyrimidinyl Peptidomimetics as Potential Antimalarial Therapeutic Agents

A class of new pyrimidinyl peptidomimetic agents (compounds 1−6) were synthesized, and their in vitro antimalarial activities against Plasmodium falciparum were evaluated. The core structure of the new agents consists of a substituted 5-aminopyrimidone ring and a Michael acceptor side chain methyl 2-hydroxymethyl-but-2-enoate. The synthesis of 1−6 featured a Baylis−Hillman reaction of various aldehydes with methyl acrylate catalyzed by 1,4-diazabicyclo[2.2.2]octane (DABCO) and a S_N2‘ Mitsunobu reaction under the conditions of diethyl azadicarboxylate (DEAD), triphenylphosphine (Ph₃P), and various acids. The new compounds exhibited potent in vitro growth inhibitory activity (IC ₅₀ = 10−30 ng/mL) against both chloroquine sensitive (D-6) and chloroquine resistant (W-2) Plasmodium falciparum clones. Compound 6 (IC₅₀ = 6−8 ng/mL) is the most active compound of the class, the antimalarial efficacy of which is comparable to that of chloroquine. In general, this class of compound exhibited weak to moderate in vitro cytotoxicity against neuronal and macrophage cells with IC ₅₀ in the range of 1−16 μg/mL and showed less toxicity in a colon cell line. Preliminary results indicated that compounds 3 and 6 are active against P. berghei, prolonged the life span of parasite-bearing mice from 6 days for untreated control to 16−24 days for drug-treated animals.