Chiral Holmium Complex-Catalyzed Synthesis of Hydrocarbazole from Siloxyvinylindole and Its Application to the Enantioselective Total Synthesis of (−)-Minovincine

The catalytic and enantioselective total synthesis of (−)-minovincine has been accomplished. The key highly substituted hydrocarbazole derivative was obtained by an asymmetric Diels–Alder reaction of siloxyvinylindole catalyzed by 0.5 mol % of a chiral holmium complex. The Diels–Alder adduct was converted to a tetracyclic intermediate in a one-pot procedure. No waste stereoisomers were produced throughout the entire total synthesis.