38 Erythrina属植物アルカロイド研究新塩基の構造と新合成法

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The alkaloidal components of the leaves, trunks, roots and seeds of Erythrina plants (Leguminosae) were systematically examined. Twelve known alkaloids were isolated and characterized. In addition, four new non-phenolic bases, which were named erysotramidine (I), crystamidine (II), erytharbine (III) and 11-hydroxyerysotrine (IV) were isolated and their structures were respectively determined. It is interesting that the isolation of (I), (II) and (III) from Erythrina species is the first example of the natural Erythrina alkaloids containing an amide group. Although syntheses of 3-oxoerythrinan have been reported by many workers, their methods seem to be tedious or show low yields in some steps in the syntheses. In our synthesis of erythrinan, 1-[2-(3-hydroxy-4-methoxyphenethyl)]-3a,4-dihydro-1H-indole-2(3H), 6(5H)-dione (22) is an important key intermediate. We described here the easy preparation of this intermediate (22) from the enol methyl derivative (18), which was obtained by the Birch reduction of benzyl amide without cleavage of amide bond. (22) was refluxed in 98% formic acid for 16 hours to give a desired tetracyclic compound, C/D-cis-15-methoxy-16-hydroxy-3,8-dioxo-erythrinan (23)(65% yield). Reduction of (23) with lithium aluminum hydride in THE gave tetrahydroerysonine (30) and its epimer at C_3-hydroxy group. Moreover, i.r. and n.m.r. spectra of the O-methyl ether of (30) were completely superimposable on those of its authentic sample (32). For the short synthetic route and easy availability of starting compounds, we think that the method reported here may be suitable to use widely for the syntheses of Erythrina alkaloids.
天然有機化合物討論会の論文
1975-10-01

38 Erythrina属植物アルカロイド研究新塩基の構造と新合成法

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