Memory of Chirality in Bromoalkyne Carbocyclization: Applications in Asymmetric Total Synthesis of Hasubanan Alkaloids.

A transition-metal-free 5- exo- dig asymmetric cyclization of α-amino ester enolates onto bromoalkynes provided a product with excellent enantioselectivity via the memory of chirality concept. This strategy was applied to a concise total synthesis of (-)-runanine and a formal synthesis of (-)-8-demethoxyrunanine and (-)-cepharatine D.