We anticipated that this could be possible by the use of chiral non racemic α,β-unsaturated γ-lactams 3 that we have been developing for some years. [2] The possibility to diastereoselectively substitute γ-lactams 3 at the C-5 position with either an electrophile [via the silyloxypyrrole, path (a)] or a nucleophile [via a N-acyliminium, path (b), Scheme [2] ], permits to construct a quaternary spiro center at this carbon. As a matter of fact, the application of path (a) maintains the α,β- ...
