Flow Thermolysis Rearrangements in the Indole Alkaloid Series: Strictamine and Akuammicine Derivatives. The Absolute Configurations of Ngouniensine and epi-Ngouniensine.
Flow thermolysis of strictamine (1) generated two of the predictable rearrangement products, resulting from [1,5]-sigmatropic shifts: akuammicine (2) and indolenine 9. Besides formation of these two compounds, a quite different pathway gave rise to a novel rearrangement leading to indole 6, with the framework of the natural alkaloid ngouniensine (19). Rearrangement to the ngouniensine skeleton became the major pathway when the akuammicine derivatives 10, 12, and 17 were submitted to thermolysis, generating compounds 11, 13 + 15, and 18, respectively. These results allowed us to assign the absolute configuration of (-)-ngouniensine (19) (3R,20R) and that of (-)-epingouniensine ((-)-21) (3R,20S).
Hugel
Georgette
G
Laboratoire de Transformations et Synthèse de Substances Naturelles et Laboratoire de Pharmacognosie, associés au CNRS, Université de Reims Champagne-Ardenne, Faculté de Pharmacie, 51 rue Cognacq-Jay, F-51096 Reims Cédex, France.
Royer
Daniel
D
Le Men-Olivier
Louisette
L
Richard
Bernard
B
Jacquier
Marie-José
MJ
Lévy
Jean
J