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Paper | Regular issue | Vol 32, No. 8, 1991, pp.1527-1535
Published online, 1st January, 1970
DOI: 10.3987/COM-91-5740
Stereoselectivity in the Preparation of Indolo[2,3-a]quinolizidine Nb-Metho-Salts

Mauri Lounasmaa* and Tarja Tamminen

*Laboratory for Organic and Bioorganic Chemistry, Technical University of Helsinki, P.O. Box 6100, FIN-02150 HUT, Espoo 15, Finland

Abstract

Stereoselective preparation of indolo[2,3-a]quinolizidine Nb-metho-salts has been studied. Although the Nb-methylation is a kinetically controlled reaction (preferential methylation at the conformation where the Nb-atom is least hindered), isomeric mixtures were obtained in all cases where the trans-quinolizidine ring juncture (conformation a) of the starting conpounds was strongly favoured. This indicates a partial conformational control of the reaction. BOC-protected compounds yielded C(12b)H-Nb-CH3 cis-products only. Since this stereochemistry is maintained in deprotection, an attractive approach is offered for the stereoselective preparation of the cis-isomers.