Synthesis 2016; 48(01): 150-160
DOI: 10.1055/s-0035-1560359
paper
© Georg Thieme Verlag Stuttgart · New York

Synthesis of the Pyrano[3,2-a]carbazole Alkaloids Koenine, Koenimbine, Koenigine, Koenigicine, and Structural Reassignment of Mukonicine

Christian Schuster
Department of Chemistry, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany   Email: hans-joachim.knoelker@tu-dresden.de
,
Marika Rönnefahrt
Department of Chemistry, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany   Email: hans-joachim.knoelker@tu-dresden.de
,
Konstanze K. Julich-Gruner
Department of Chemistry, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany   Email: hans-joachim.knoelker@tu-dresden.de
,
Anne Jäger
Department of Chemistry, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany   Email: hans-joachim.knoelker@tu-dresden.de
,
Arndt W. Schmidt
Department of Chemistry, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany   Email: hans-joachim.knoelker@tu-dresden.de
,
Hans-Joachim Knölker*
Department of Chemistry, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany   Email: hans-joachim.knoelker@tu-dresden.de
› Author Affiliations
Further Information

Publication History

Received: 30 September 2015

Accepted: 01 October 2015

Publication Date:
08 October 2015 (online)


Abstract

Using the palladium(II)-catalyzed oxidative cyclization of a diarylamine and the annulation of a dimethylpyran ring by Lewis acid promoted reaction with prenal as key steps, the total syntheses of the 6-oxygenated pyrano[3,2-a]carbazole alkaloids koenine and koenimbine, and of the 6,7-dioxygenated pyrano[3,2-a]carbazole alkaloids koenigine and koenigicine (koenimbidine, koenidine) were achieved. Moreover, these studies led to an improved synthetic route to the 2,6-dioxygenated carbazole alkaloid glycozolidol. Mukonicine, originally published as 6,8-dimethoxypyrano[3,2-a]carbazole, was found to be identical with koenigicine.

Supporting Information