Six regioisomers assocd. with the tricyclic core of thiaplakortones A-D have been synthesized. Reaction of 1H-indole-4,7-dione and 1-tosyl-1H-indole-4,7-dione with 2-aminoethanesulfinic acid afforded a regioisomeric series, which was subsequently deprotected and oxidized to yield the tricyclic core scaffolds present in the thiaplakortones. All compds. were fully characterized using NMR and MS data. A single crystal X-ray structure was obtained on one of the N-tosyl derivs. All compds. were screened for in vitro antiplasmodial activity against chloroquine-sensitive (3D7) and multidrug-resistant (Dd2) Plasmodium falciparum parasite lines. Several analogs displayed potent inhibition of P. falciparum growth (IC50 < 500 nM) but only moderate selectivity for P. falciparum vs. human neonatal foreskin fibroblast cells.