Highly stereoselective asymmetric 6pi-azaelectrocyclization utilizing the novel 7-alkyl substituted cis-1-amino-2-indanols: formal synthesis of 20-epiuleine

Highly stereoselective asymmetric 6pi-azaelectrocyclization was achieved with generality, based on the reaction between the (E)-3-carbonyl-2,4,6-trienal compounds and the (-)-7-alkyl-cis-1-amino-2-indanol derivatives as the effective novel chiral amines. Furthermore, the chiral auxiliaries of the cyclized products obtained were efficiently removed by the novel manganese dioxide oxidation under remarkably mild conditions, and the method was successfully applied to the formal synthesis of optically active 20-epiuleine.