Synthesis of enantiomerically pure hydrinden-2-ones and benz[e]inden-2-ones via asymmetric alkylations of chiral bicyclic lactams

A route to the titled compounds in >99% ee was achieved from sequential diastereoselective alkylations of chiral, nonracemic bicyclic lactams 6 and 15. An intramolecular addition of the organolithium species derived from 17a-c and 28a-d gave, after hydrolysis, diketones 25a-c and 30a-d, which were cyclized to the titled compounds 4a-c and 31a-d. As an example of the versatility of this method, the ABC ring system of the triterpene stelliferin A, isolated from marine organisms, was prepared in high enantiomeric excess