Asymmetric Synthesis of (−)-Nupharamine and (−)-(5 S ,8 R ,9 S )-5-(3-Furyl)-8-methyloctahydroindolizidine from β-Amino Ketones and the Intramolecular Mannich Reaction

The asymmetric synthesis of the 2,3,6-trisubstituted piperidine core of the antitumor Nuphar alkaloids was readily achieved by using the intramolecular Mannich reaction and a sulfinimine-derived beta-amino ketone.