Diastereoselective conjugate addition/cyclization/bromination: Access to four stereocenters in a single step

A stereoselective tandem conjugate addition reaction with a chiral amine-derived nucleophile is reported in which the enolate intermediate is quenched with 1,2-dibromotetrachloroethane as a mild brominating reagent. X-ray analysis of a subsequent derivative was used to prove the configuration at each of the four newly formed stereocenters. The resulting α-bromoester underwent selective transesterification catalyzed by mild base to allow selective manipulation of the two ester groups of the product.