Stereoselective synthesis of 2,6-cis- and 2,6-trans-piperidines through organocatalytic aza-Michael reactions: a facile synthesis of (+)-myrtine and (-)-epimyrtine.

Both 2,6-cis- and 2,6-trans-piperidines were prepared from common substrates through organocatalytic aza-Michael reactions promoted by the gem-disubstituent effect in conjunction with dithiane coupling reactions. The organocatalytic aza-Michael reaction enabled a facile synthesis of (+)-myrtine and (-)-epimyrtine from a common substrate.