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Paper | Regular issue | Vol 53, No. 8, 2000, pp.1697-1711
Published online, 1st January, 1970
DOI: 10.3987/COM-00-8875
Synthesis of Pentacyclic Ring Systems, Indolo[2,3-a][1,2]oxazino[5,6-i]quinolizine and Indolo[2,3-a]pyrano[3,2-i]quinolizine, and Their Application for the Synthesis of Eburnamine-Vincamine Alkaloids

András Nemes,* János Kreidl, László Czibula, Katalin Nógrádi, Mária Farkas, Csaba Szántay Jr., Gábor Tárkányi, Gábor Balogh, Ida Juhász, Alajos Kálmán, and László Párkányi

*Chemical Works of Gedeon Richter Ltd., Technological Research Laboratory No.I, Budapest 10, P. O. Box 27, H-1475 Budapest, Hungary

Abstract

15a-Ethyl-14-carboxylic esters of the title pentacycles (6) and (8) were prepared via Wenkert’s enamine (4). Both compounds can be readily transformed into indoloquinolizinylpyruvate oxime esters (5), key intermediates for the synthesis of vincamine alkaloids. The ring/chain equilibrium observed for compounds (6) and (8) was studied by UV and NMR spectroscopic methods.