The reaction of Ge-masked dienolates with Michaelacceptors in the presence of Lewis acids produced the 1,4-γ adduct regioselectively, whereas the reaction in the presence of Bu4NF gave the 1,4-α adduct exclusively.
Either the α- (3) or γ-amino acid derivatives (4) can be prepared with very high regioselectivity by treating diethyl azodicarboxylate (DEAD) with (i) lithium dienolates themselves (2) in certain cases, (ii) Sn-masked dienolates (5), or (iii) Ge-masked dienolates (6).