Stereoselective synthesis of 2,6-disubstituted 3-piperidinols: application to the expedient synthesis of (+)-julifloridine

[reaction: see text] The asymmetric synthesis of 2,6-disubstituted 3-piperidinols having a 2,3-cis and 2,6-trans relative stereochemistry was accomplished in three steps using the following sequence: stereocontrolled nucleophilic addition of an organomagnesium reagent to a chiral pyridinium salt; monohydrogenation of the resulting 2-substituted 1,2-dihydropyridine; and a one-pot, highly diastereoselective epoxidation-nucleophilic addition with a heteroatom nucleophile or an organometallic reagent. This methodology was applied to the expedient asymmetric synthesis of (+)-julifloridine in four steps.