Total Synthesis of Notoamides F, I, and R and Sclerotiamide.

The total synthesis of the natural indole alkaloids (+)-notoamide F, I, and R and (-)-sclerotiamide is described. The four heptacyclic compounds were synthesized in 10-12 steps in a convergent and highly stereoselective manner from the readily available Seebach acetal. Key steps of the synthesis include a stereoselective oxidative aza-Prins cyclization to construct the bicyclo[2.2.2]diazaoctane, and a cobalt-catalyzed radical cycloisomerization to create the cyclohexenyl ring.