54(P18) 海洋産脂質過酸化抑制インドールアルカロイドMartefragin Aの合成と活性(ポスター発表の部)

概要

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Martefragin A (1) is a new type of indole alkaloid of marine origin, which was isolated from the marine red alga Martensia fragilis collected at Toyama Bay, and exhibits potent antiperoxidation activity of lipid. We focused our interest on the asymmetric synthesis of four possible stereo isomers of 1 in order to determine the absolute configuration of 1 as well as to investigate the structure-activity relationship. Here we present the first efficient and highly enantioselective synthesis of 1. Starting from the chiral (S)-2-methylbutyl iodide, we developed a four step route to generate (S)-4-methylhexanoyl chloride, which was converted to 7a via 14 by use of Evans methodology. The oxidative cyclization of the dipeptide 16, obtained from 7c and L-tryptophan benzyl ester, was accomplished using DDQ to give 17 (63%). Further synthetic manipulations involve deprotection of the nitrogen, dimethylation of amino group and hydrogenolysis of the benzyl ester to afford the martefragin A, (1"S, 3"S)-1. The absolute configuration of 18 was established by X-ray structure analysis. The synthesis of other isomers of 1 and related compounds, and structure-activity relationship will be presented.
天然有機化合物討論会の論文
1997-07-20