Previously unreported 6-substituted 4-alkylidene(arylidene)hydrazono-1,3-oxazinan-2-ones and a series of open-chained 3-hydroxy-N′-alkylidene(arylidene)propanehydrazonamides were synthesized and evaluated for their in vitro antiplasmodial activity. The most active 3-hydroxy-N′-alkylidene(arylidene)propanehydrazonamide exhibits potent in vitro antiplasmodial activity against the chloroquine-sensitive strain 3D7 of Plasmodium falciparum and demonstrates an IC50 value of 0.2 µM.