Stereodivergent synthesis of enantiopure cis- and trans-3-Ethyl-4-piperidineacetates.

[reaction: see text] Starting from a common chiral bicyclic lactam 11, enantiopure trans- or cis-3-ethyl-4-piperidineacetate derivatives are obtained by conjugate addition of an enolate or a cuprate to the unsaturated lactams 12 or 18, respectively.