An efficient synthesis of 1-azadienes derived from α-aminoesters is achieved through an aza-Wittig reaction of phosphazenes with β,γ-unsaturated α-ketoesters. Regioselective 1,2-reduction of these functionalized 1-azadienes affords vinylglycine derivatives, while conjugative 1,4-reduction gives α-dehydroamino acid compounds. Reduction of both the carbon−carbon and the imine−carbon−nitrogen double bonds leads to the formation of α-amino acid derivatives.