Studies on the constituents of Thai medicinal plants

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Chemical studies of the constituents of some Thai medicinal plants, mainly focused on indole alkaloids, were carried out based on our botanical survey in 1984.1. New type seco alkaloids of Uncaria salaccensis; From this Rubiaceae plant four new alkaloids were obtained. Three of them possessed the novel 20,21-dioxo-20,21-secoframework modified from the conventional oxindole alkaloid structure. The remaining one was a 3-oxo-7-hydroxy-3,7-seco-type alkaloid.2. Alkaloids of Kopsia jasminiflora; Five new alkaloids were isolated. Kopsijasminilam was an alkaloid having the novel 20-hydroxy-21-oxo-20,21-seco-aspidofractinine skeleton. Deoxykopsijasminilam and ^<14>-kopsijasminilam were additional members of the same structural class of alkaloids.3. Chemical studies on the alkaloids of Gelsemium elegans; Eight new alkaloids were found in the titled Loganiaceae plant and their structures were determined. The structure of koumidine which was previously presented was revised. Studies on biogenetically patterned synthesis of this gruop of alkaloids were also carried out.4. Constituents of a bitter plant, Vernonia extensa; A new type sterol glucoside was found in the titled compositae plant. Chemical and spectroscopical studies clarified that this compound had a tetracyclic sterol framework possessing <@17,9(11)<@D1-heteroannular conjugated diene and a novel highly-oxygenated side chain structural moiety.