Stereoselective Synthesis Diastereoselective Synthesis of b-Ether Derivatives of Artemisinin, an Antimalarial Drug: The Effect of Nitrile on Stereoselectivity

Malaria is a life-threatening disease affecting a major portion of the world’s population with considerable loss of human life. Artemisinin, isolated from Artemisia annua, its oiland water-soluble derivatives, and other known antimalarials are recommended for artemisinin combination therapy by the World Health Organization. We have established a method for the stereoselective synthesis of bether derivatives of dihydroartemisinin in high yield and high diastereoselectivity. The reaction either in acetonitrile or dichloromethane/trichloroacetonitrile (6:1) mixtures at 0 8C or room temperature, respectively, furnished the antimalarial drugs artemether 3 or arteether 4 in high yield with a high diastereomeric ratio. The effect the nitrile has on the yield and stereoselectivity is mechanistically explained.