Stereoselective formation of tetrahydrofuran rings via [3 + 2] annulation: total synthesis of Plakortone L.

The [3 + 2] annulation of 2,3-O-isopropylidene-aldehydo-aldose with methallyl ether leads to the stereoselective formation of a substituted tetrahydrofuran system, which is converted to a bicyclic lactone derivative via consecutive deprotection, oxidative cleavage of the terminal diol, oxidation of the resulting lactol, and Barton–McCombie deoxygenation. The efficiency of this process was demonstrated by the first total synthesis of Plakortone L.