Squaric acid/4-aminoquinoline conjugates: novel potent antiplasmodial agents.

We report the synthesis and structure-activity relationship (SAR) analysis of a series of hybrid compounds containing a squaric moiety conjugated with heterocyclic moieties from well-known antimalarials. This novel series of compounds presents improved antiplasmodial activity compared with the squaric derivatives described in our previous work. Three compounds, 8b (IC₅₀ = 99 nM), 8c (IC₅₀ = 95 nM), and 8d (IC₅₀ = 105 nM) had greater in vitro potency than chloroquine 1 (IC₅₀ = 140 nM) against chloroquine resistant Plasmodium falciparum. In addition, they were noncytotoxic against NIH 3T3 and Hek 293T cells.