16 淡水産原生動物テトラヒメナのタオリン脂質母核、テトラヒドロキシステアリン酸の絶対配置決定(口頭発表の部)

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A series of taurolipids has been isolated from a fresh-water protozoan Tetrahymena thermophila, and their unique chemical features have been clarified as: taurolipid A; 2-(3-acyloxy-7,13-dihydroxyoctadecanoylamino)ethanesulfonic acid, taurolipid B (2); 2-(3-acyloxy-2,7,13-trihydroxyoctadecanoylarnino)ethanesulfonic acid, taurolipid C; 2-(3-acyloxy-2,7,12,13-tertrahydroxy-octadecanoylamino)ethanesulfonic acid. Taurolipid B exhibits growth-inhibitory activity against HL-60. Methanolysis of taurolipid B gives a tetrahydroxy compound (3), which possesses four asymmetric centers. This paper describes determination of the absolute configuration of the four hydroxy groups of 3 by using 2ATMA (1; 2-anthrylmethoxyacetic acid), a newly developed chiral anisotropic reagent. The vicinal hydroxy groups of 3 at C-2 and 3 were protected by dimethylacetalization (acetone/CuSO4/H^+) to give acetonide (4). This compound was treated with 1.0eq (S)-2ATMAIEDC/DMAP/CH_2Cl_2, giving a mixture of mono-2ATMA esters(5 and 6)together with a small amount of di-2ATMA ester (7). Figure 1 shows the ^1H-NMR spectra of 5 (a) and 6 (b), in which the protons on the same side of the anthracene ring (see conformation 1a) shift upfield remarkably. The shifted signals were easily assigned to the protons denoted in the respective spectra, and 7R, 13S configuration was determined. It should be noted that only one enantiomer of 2ATMA was necessary to elucidate the absolute configuration owing to the strong anisotropic effect of 2ATMA. To confirm the proposed absolute configuration, 4 was treated with 1.0eq. (R)-2ATMA, affording monoesters 8 and 9. TheΔδvalues (δR-δS) were calculated and they are shown in 8a and 9a, which completely verified the absolute configuration at 7 and 13 positions. The absolute configuration of the glycol at C-2 and 3 were determined by combined usage of CD and 2ATMA: By analyzing the NMR pattern of the dimethyl-1,3-dioxolane moiety of 4, the threo relationship of the two hydroxy groups was established. 4 was converted into dianisoate 12, which showed positive split Cotton effect, thus leading 2S,3R configuration. This absolute configuration was also supported by the 2ATMA method. All these experiments lead to 2S, 3R, 7R, 13S configuration of the tetrahydoxystearate.
天然有機化合物討論会の論文
1996-09-02

16 淡水産原生動物テトラヒメナのタオリン脂質母核、テトラヒドロキシステアリン酸の絶対配置決定(口頭発表の部)

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