Decarbonylation of α-tertiary amino acids application to the synthesis of polyhydroxylated indolizidines from D,L-pipecolic acid

Abstract

The decarbonylation of the bicyclic α-tertiary carboxamido acid 11 led to the enamide 12, easily transformed into the indolizidine alkaloid 8,8a- trans-8-hydroxy-indolizidine 14. Likewise, the same process applied to the α-substituted pipecolic acid derivative 5 led to the unsaturated ester 6 which was easily transformed either into δ-coniceine 9 or to 14. The thermal fragmentation of the acyl derivative 22 led to the enamide 24 which has been transformed into (±)-swainsonine 26.