Conjugate Addition of Organocuprates to Chiral Bicyclic δ-Lactams. Enantioselective Synthesis of cis-3,4-Disubstituted and 3,4,5-Trisubstituted Piperidines

[reaction: see text] Chiral nonracemic bicyclic lactam 3, easily accessible by cyclodehydration of (R)-phenylglycinol and racemic methyl 4-formylhexanoate, was converted to the unsaturated lactams 5, which undergo the stereoselective conjugate addition of lower order cyanocuprates to ultimately lead to enantiopure cis-3,4-disubstituted and 3,4,5-trisubstituted piperidines.