Copper ion-catalyzed regioselective introduction of active methylene groups into the γ-position of piperidine skeleton and its application to the synthesis of (−)-cincholoiponic acid

Copper ion-catalyzed regioselective introduction of active methylene groups into the γ-position of piperidine skeleton was exploited. In the case of using chiral ligand as an additive, this reaction proceeded with moderate enantioselectivities. This method was applied to the synthesis of (−)-cincholoiponic acid from N-methoxycarbonylpiperidine.