Iodocyclization and Prins-type macrocyclization: an efficient formal synthesis of leucascandrolide A.

The formal total synthesis of leucascandrolide A has been achieved in 20 steps from a known epoxide with an overall yield of 11.5% following a recently developed strategy for the construction of trans-2,6-disubstituted-3,4-dihydropyrans and a Lewis acid catalyzed intramolecular Prins-cyclization of an aldehydic homoallylic alcohol to generate the tetrahydropyran ring with three stereogenic centers and macrocycle concomitantly.