Design and synthesis of potent antileishmanial cycloalkylidene-substituted ether phospholipid derivatives

Two series of novel ether phospholipids (EPs) have been synthesized. The first includes cyclodecylidene- or cyclopentadecylidene-substituted EPs carrying N,N,N-trimethylammonium or N-methylpiperidino or N-methylmorpholino head groups. The second series encompasses more rigid head groups in combination with cycloalkylidene moieties in the lipid portion. In addition, hydrogenated derivatives were obtained. All the new analogues, except 33, were 1.5- to 62-fold more potent than miltefosine against the intracellular L. infantum, and the most active ones were also less cytotoxic against the human monocytic cell line THP1 and less hemolytic than miltefosine. The analogues that combine high potency with low cytotoxicity and hemolytic activity were 19, 37, 21 23, 38, 39, and 40. Cyclopentadecylpentylphosphocholine (38) possesses an IC50 of 0.7 microM against L. infantum amastigotes and is the least cytotoxic analogue, since it does not present toxicity against THP1 macrophages, even at a concentration that is 800-fold the antiparasitic IC50 value, and does not present significant hemolytic activity.