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Note | Regular issue | Vol 45, No. 7, 1997, pp.1397-1404
Published online, 1st January, 1970
DOI: 10.3987/COM-97-7816
Synthesis and Conformational Study of Indolo[2,3-a]quinolizidine-3-ethan-1'-ols: Intermediates for the Synthesis of Deplancheine and Flavopereirine

Mauri Lounasmaa,* Kimmo Karinen, and Arto Tolvanen

*Laboratory for Organic and Bioorganic Chemistry, Technical University of Helsinki, P.O. Box 6100, FIN-02150 HUT Espoo, Finland

Abstract

The synthesis and stereostructures of all four indolo[2,3-a]quinolizidine-3-ethan-1’-ols are described. The two alcohols with an axial side chain exist principally in the conformation where the C/D ring junction is trans, which is favoured by an intramolecular hydrogen bond between the hydroxyl group and the Nb-atom. Dehydration of the four alcohols with P2O5 in each case led to a mixture consisting of E-deplancheine and Z-deplancheine. The three side products were two 3-vinyl isomers, one of which can be converted to deplancheine via double bond isomerization, and 3-ethyl-1,4,6,7,12,12b-hexahydroindolo[2,3-a]quinolizine, which is a precursor of flavopereirine.