An enantioselective approach to 2-alkyl substituted tetrahydroquinolines: total synthesis of (+)-angustureine

A simple and highly efficient synthetic approach to enantiopure 2-alkyl substituted tetrahydroquinoline 1 skeleton from aldehydes as starting materials and its application to the total synthesis of (+)-angustureine 2 is described. Key transformations include proline catalyzed aminoxylation, Corey-Fuchs protocol, Sonogashira coupling and intramolecular Mitsunobu reactions.