Development of a Samarium Based Allylic Benzoate Elimination/Isomerization: Application to a Total Synthesis of Honokiol

We have developed a new samarium diiodide-mediated elimination/isomerization reaction of benzoyl esters, capable of delivering olefinic products with high yield and selectivity depending on substrate structure and the additives used. The ability to selectively synthesize terminal, non-conjugated alkene substituents inspired us to use these optimized conditions in order to complete the total synthesis of the natural product, honokiol. Honokiol is a biaryl natural product isolated from magnolia trees that displays desirable oncological properties as evidenced by several biological studies in recent years. We found that our initially proposed pathway for completing the synthesis of honokiol was not a feasible route due to the sensitivity of the allylic groups. However, after adjusting our synthetic route, we were able to complete the synthesis of honokiol in 40% overall yield.