Total Syntheses of (-)-Minovincine and (-)-Aspidofractinine Using Chain of Cascade Reactions.

: We report eight-step syntheses of (-)- minovincine and (-)-aspidofractinine using easily available and inexpensive reagents and catalyst. A key element of the strategy was the utilization of the chain of cascade reactions to rapidly construct the penta- and hexacyclic frameworks. These cascade transformations included organocatalytic Michael-aldol condensation, a multistep anionic Michael-S N 2 cascade reaction and Mannich reaction interrupted Fischer indolization. To streamline the synthetic routes, we also investigated the deliberate use of steric effect to secure various chemo- and regioselective transformations.