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Note | Regular issue | Vol 45, No. 2, 1997, pp.361-366
Published online, 1st January, 1970
DOI: 10.3987/COM-96-7675
Lactone Formation as an Aid in the NMR Characterization of Two 3-(1'-Hydroxyethyl)indolo[2,3-a]qunolizidine-1-carboxylates: Intermediates for the Stereoselective Synthesis of Tacamine-Type Indole Alkaloids

Mauri Lounasmaa,* Kimmo Karinen, David Din Belle, and Arto Tolvanen

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

Abstract

NMR spectral characterization of methyl 3-(1’-hydroxyethyl)-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinolizine-1-carboxylates (3) and (4) is described. The configuration at the hydroxyethyl side chain was confirmed by NOE difference spectroscopy performed on 3-(1’-hydroxyethyl)-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinolizine-1-carboxylic acid lactones (5) and (6) obtained by epimerization of 3 and 4. Base treatment of 3 and 4, followed by esterification, led to methyl 3-(1’-hydroxyethyl)-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinolizine-1-carboxylates (7) and (8), which are new intermediates for the preparation of tacamine-type indole alkaloids.