Enantioselective total synthesis of (+)-ophiobolin†A.

The enantioselective total synthesis of (+)-ophiobolin A is described. This total synthesis features the construction of the spiro CD ring of (+)-ophiobolin A through a stereoselective intramolecular Hosomi-Sakurai cyclization reaction, the joining of the A ring to the CD ring by using a reaction reported by Utimoto, and the construction of the ophiobolin eight-membered carbocyclic ring through ring-closing metathesis (RCM), which was performed for the first time in this study. This successful RCM reaction required the use of a substrate that contained either a benzyloxy or a methoxymethoxy group at the C5 position and either an isopropenyl group or its hydroxylated form at the C6 position.