Asymmetric synthesis of Sedum alkaloids via lithium amide conjugate addition

Conjugate addition of lithium (R)-N-allyl-N-(α-methylbenzyl)amide or lithium (R)-N-but-3-enyl-N-(α-methylbenzyl)amide to an alkyl hexa-2,4-dienoate or alkyl hepta-2,6-dienoate, followed by ring-closing metathesis of the olefin functionalities within the resultant β-amino ester, generates a range of diastereoisomerically pure azacycles in good yield. These homochiral templates are readily transformed to a range of piperidine alkaloids of the Sedum family, and the corresponding five-, seven- and eight-membered ring homologues.