Intramolecularconjugateaddition of γ-substituted (E)-α,β-unsaturated ketones with a Lewis acid (BF 3 ·OEt 2 ) selectively afforded trans-2,3-disubstituted piperidine derivatives. Chiral substrates were synthesized by Sharpless asymmetric dihydroxylation of the enamine; the antimalarial compound febrifugine was synthesized from the major product of the conjugateaddition reaction.