42 二重分子インドールアルカロイドgardmultineの構造

概要

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Formerly we reported the isolation and characterization of gardmultine (I), a bisindole alkaloid of Gardneria multiflora Makino (Loganiaceae), under a tentative name of alkaloid E. Further chemical and spectroscopic study has led us to the conclusion that its monomeric components should be gardnera-mine (II) and chitosenine (IV), and that the structure of gardmultine is best expressed by the formula (I) shown in the text. The proposed structure (I) was supported by the following observations; Treatment of I with acetic acid or dilute hydrochloric acid gave rise to the respective dimeric oxindoles (III) and (VI), thus revealing the unique amide acetal system (B) in I. Introduction of acetate or chloride residue into the product can be explained by the mechanism shown in chart 4. A closely similar reaction had been found by us in our structural work on gardneramine(II)(chart 3). A methanesulfonate (IX) which was prepared from diol (VIII) by usual mesylation gave the starting base, gardmultine (I), on treatment with KOtBu in tBuOH (chart 5). Inspection of the stereostructure (I) using a stereo model reveals shielding effect of the aromatic ring (A) on the C_<18>,-olefinic methyl group whose NM R signal is observed atδ 0.88. Biogenetic type synthesis of I using gardneramine (II) and an appropriately functionalized derivative of chitosenine (IV) is now under progress. (chart 6).
天然有機化合物討論会の論文
1973-10-01