A Novel C₂-Symmetric 2,6-Diallylpiperidine Carboxylic Acid Methyl Ester as a Promising Chiral Building Block for Piperidine-Related Alkaloids^†

C₂-Symmetric 2,6-diallylpiperidine 1-carboxylic acid methyl ester (5) was examined via the double asymmetric allylboration of glutaraldehyde followed by aminocyclization and carbamation as a promising chiral building block for piperidine-related alkaloids, which were synthesized by the desymmetrization of 5 using intramolecular iodocarbamation as a key step.