Diastereoselective isothiourea iodocyclization for manzacidin synthesis

We have devised a novel strategy for the total synthesis of the manzacidins. Our approach utilizes an isothiourea iodocyclization strategy to directly form the heterocyclic core, and in the process induce stereoselectivity at the quaternary center. We have found that cyclization can be achieved using an isothiourea as the nucleophilic partner. Cyclization proceeds smoothly using IBr at low temperature, affording an advanced intermediate along our proposed route to manzacidin A in 92% yield. We have demonstrated the scope of the reaction by preparing several cyclic isothioureas, including an intermediate on our proposed route for the synthesis of manzacidin D.