Synthesis and antimalarial activity of quinones and structurally-related oxirane derivatives.

A series of eighteen quinones and structurally-related oxiranes were synthesized and evaluated for in vitro inhibitory activity against the chloroquine-sensitive 3D7 clone of the human malaria parasite Plasmodium falciparum. 2-amino and 2-allyloxynaphthoquinones exhibited important antiplasmodial activity (median inhibitory concentrations (IC50) < 10 μM). Oxiranes 6 and 25, prepared respectively by reaction of α-lapachone and tetrachloro-p-quinone with diazomethane in a mixture of ether and ethanol, exhibited the highest antiplasmodial activity and low cytotoxicity against human fibroblasts (MCR-5 cell line).

2,3-Dihydro-3,3-dimethylspiro[1H-4-oxanthracene-5,2'-oxiran]-10(5H)-one.

The central six-membered ring in the title compound, C(16)H(16)O(3), is almost planar (and almost coplanar with the aromatic ring), despite one of its C atoms being formally sp(3) hybridized. The planarity is a consequence of the C atom at the centre of the spirocyclic system also being part of the three-membered epoxide ring. The molecules are linked by pi-pi and C-H.