Insight into the mechanism of action of plakortins, simple 1,2-dioxane antimalarials

A multidisciplinary approach, based on molecular dynamics/mechanics, ab initio calculations, dynamic docking studies, and chemical reactions, has been employed to gain insight into the mechanism of the antimalarial action of plakortin and dihydroplakortin, simple 1,2-dioxanes isolated from the sponge Plakortis simplex. Our results show that these molecules, after interaction of the endoperoxide bond with Fe(ii), likely coming from the heme molecule, give rise to the formation of an oxygen radical, followed by rearrangement to give a carbon radical centered on the "western" alkyl side-chain. The carbon radicals generated on the side-chain, amenable for intermolecular reactions, should represent the toxic intermediates responsible for subsequent reactions leading to plasmodium death. The minimal structural requirements necessary for the activity of this class of antimalarial agents have been identified and discussed throughout the paper.

Stable spiro-endoperoxides by sunlight-mediated photooxygenation of 1,2-O-alkylidene-5(E)-eno-5,6,8-trideoxy-alpha-D-xylo-oct-1,4-furano-7-uloses

Sunlight-mediated photooxygenation of 3-O-acetyl and 3-O-methyl derivatives of 1,2-O-alkylidene-5(E)-eno-5,6,8-trideoxy-alpha-D-xylo-oct-1,4-furano-7-uloses (1a-e) in carbon tetrachloride solution gave stable 4,7-epidioxy derivatives in 4R (2a-e) and 4S (3a-e) configurations. The presence of an endo alkyl, on the 1,2-O-alkylidene group and its size, resulted in an increase of the yield of the 4S isomers. 3-O-acetyl derivatives yielded products as a mixture of C-7 anomers, whereas 3-O-methyl derivatives gave pure single stereoisomers.

Antimalarial cyclic peroxy ketals

Over 20 new, cyclic, peroxy ketals have been prepared via a two-step protocol starting with readily available aryl methyl ketones. Structure-activity correlations using in vitro antimalarial data as a guide for optimization of potency have led to the design and synthesis of seven new peroxides that have IC50 values of 31-85 nM (artemisinin IC50 = 8.4 nM). Some SAR generalizations are discussed.