In this thesis manuscript are described our synthetic efforts and the first total synthesis of two natural products isolated from the sponges of the genus Plakortis. In total, two different synthetic approaches were studied to finally accomplish the synthesis of plakortolide I. The first approach is an extension of the method developed by our group which consists in the creation of the 1,2-dioxane cycle by intramolecular opening of vinyl epoxide with β-hydroperoxy group. Firstly, we was interested in the preparation of alkoxymethylhexa-2,5-dien-1-ol. We have also tried to create the 1,2-dioxane cycle by double opening of bis-1,5-epoxide with hydrogen peroxide. Further more we have synthesised trisubstituted β-hydroperoxy vinyl epoxide, precursor of 1,2-dioxan ring, from R-epichlorohydrin. During this synthesis a procedure of chemoselective methylenation of ketone in the presence of epoxide by Nysted reagent and Ti(OiPr)2Cl2 was developed. Finally, (-)-ent-plakortolide I and seco-plakortolide E were synthesised by intramolecular Michael addition of hydroperoxide to double bond of the butenolide moiety
