We report that the stereochemical outcome of the conjugate addition of organocopper reagents to bicyclic α,β-unsaturated lactams derived from pyroglutaminol is determined by the nature of the aminal group. Bicyclic α,β-unsaturated lactams in which the aminal is derived from a ketone have been found to afford products of syn conjugate addition. By contrast, bicyclic α,β-unsaturated lactams in which the aminal is derived from an aldehyde afford products of anti conjugate addition. These remarkably different results obtained from very similar starting materials are unexpected.