Total syntheses of four possible stereoisomers of resolvin E3

Resolvin E3, 17,18-dihydroxy-5Z,8Z,11Z,13E,15E-eicosapentaenoic acid, is a potent anti-inflammatory lipid mediator. To determine the stereochemistries of the C17- and C18-hydroxy groups of resolvin E3 and to supply a sufficient amount of material for future biological studies, we developed a highly convergent and practical route to its four possible stereoisomers. The key reactions employed here were the Horner-Wadsworth-Emmons coupling, the two copper(I)-mediated reactions between the alkynes and the propargyl tosylates, and the simultaneous reduction of the three triple bonds to the three Z-olefins.