Using predictions from heme− quinoline antimalarial complex structures, previous modifications of chloroquine (CQ), and hypotheses for chloroquine resistance (CQR), we synthesize and assay CQ analogues that test structure− function principles. We vary side chain length for both monoethyl and diethyl 4-N CQ derivatives. We alter the p K a of the quinolyl N by introducing alkylthio or alkoxy substituents into the 4 position and vary side ...