Highly Diastereo- and Enantioselective Synthesis of α-Spiro-δ-lactams by an Organocascade Reaction

An asymmetric synthesis of α-spiro-δ-lactam via organocascade reaction from easily accessible starting materials is reported. The catalytic sequence undergoes enantioselective Michael addition of β-ketoamide to α,β-unsaturated aldehyde catalysed by a secondary amine catalyst, followed by hemiaminal annulation. Optically enantiopure compounds with two contiguous stereogenic centres are obtained in good yields and excellent selectivities (up to >20:1 dr and up to >99% ee).