Plasmodium falciparum: role of absolute stereochemistry in the antimalarial activity of synthetic amino alcohol antimalarial agents.

The (+)-isomers of mefloquine and its threo analog are 1.69 to 1.95 times more active than the (-)-isomers against chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum in vitro. This large a differential between the activity of (+)- and (-)-isomers was not observed for other synthetic amino alcohol antimalarial agents containing a piperidine ring. The enantiomers of amino alcohol antimalarial agents in which the amine is part of an acyclic group, such as in halofantrine, displayed little, if any, differential antimalarial activity. Thus, the effect of absolute stereochemistry of the amino alcohol antimalarial agents on antimalarial activity appears to depend upon both the flexibility of the amine portion of the molecule and the structure of the aromatic portion of the molecule.