1 インドールアルカロイドの合成研究

概要

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A general synthesis of the indoloquinolizidine nucleus of the indole alkaloids of the ajmalicinoid and yohimboid types is described. The new method concists of γ-alkylation of N-alkyl-β-acylpyridinium salts with carbon nucleophiles, acid-induced cyclization of the resultant 1,4-dihydropyridine product and further elaboration of the thus-formed indoloquinolizideine. The ajmalicinoid ring system was formed by the exposure of 1-tryptophyl-3-acetylpyridinium bromide (Ia) to sodio dimethylmalonate and then to hydrogen bromide, followed by hydrogenation of the resultant vinylogus amide (IIIa). Subsequent reduction and dehydration of the products led to the racemates of the alkaloids tetrahydroalstonine and akuammigine as well as isomers of ajmalicine. A study of the same reaction sequence (Id→IId→IIId) was undertaken emanating from methyl β-(β-pyridyl-)acrylate and turned into total syntheses of yohimbine and pseudoyohimbine.
天然有機化合物討論会の論文
1978-08-22