Asymmetric Construction of Three Contiguous Stereogenic Centers by Conjugate Addition-Alkylation of Lithium Ester Enolate

A chiral ligand- and lithium amide-assisted asymmetric conjugate addition of lithium enolate of propionate to cyclopentenecarboxylate gave the corresponding lithium enolate, whose allylation gave the key intermediate of the marine alkaloid halichlorine as a single diastereomer with moderate enantioselectivity.