SYNTHESIS OF 1-ETHYL-1,2,3,4,6,7-HEXAHYDROINDOLO-2,3a-QUINOLIZINIUM PERCHLORATE——KEY INTERMEDIATE OF VINCAMINE

This paper describes a new route for the synthesis of 1-ethyl-1,2,3,4, 6, 7-hexahydroindolo-2, 3a-quinolizinium perchlorate(Ⅹ), from which several vinca alkaloids such as vincamine(Ⅰ) and apovincamine(Ⅱ) can be synthesized. Adopting Fischer indole synthesis with common chemicals, this route by-passed the use of the expensive tryptamine. Tautomerism was observed in 1-o-carboxybenzamido-octane-4,5-dione-4-phenyihydrazone(Ⅳa) and in 1-propyl-3, 4-dihydro-β-carboline(Ⅶ).