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.