Total Synthesis of (-)-Neocosmosin A via Intramolecular Diels-Alder Reaction of 2-Pyrone

A new synthetic route to (-)-neocosmosin A was devised by elaboration, of intramolecular Diels- Alder (IMDA) cycloaddition of 2-pyrone containing a bromopropiolate group as the dienophile. The IMDA reaction was accompanied by cycloreversion of carbon dioxide to give benzannulated macrolide with two bromide groups at C14 and C16. Installation of the pinacolboryl groups and oxidations allowed completion of the total synthesis of (-)-neocosmosin A.This work was supported by grants from the National Research Foundation of Korea (2014R1A5A1011165 and 2012M3A7B4049657)