The work presented in this thesis mainly describes the development of new reactions of β-lithiooxyphosphonium ylides to access stereodefined substituted alkenes in a highly convergent fashion.

Firstly, β-lithiooxy ylides prepared from aldehydes and phosphonium ylides were shown to react with halogen electrophiles to provide a highly stereoselective route to E-alkenyl bromides and iodides. This methodology was successfully applied to the first total synthesis of naturally oc...