P-36 ヤブコウジ科植物モクタチバナより得られたArdisiaquinone類と5-リポキシゲナーゼ阻害活性(ポスター発表の部)

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In pursuit of new 5-lipoxygenase inhibitors in natural products, we have continued to screen inhibitory activity of the plant extracts against 5-lipoxygenase by using enzyme from guinea pig peritoneal polymorphonuclear leukocytes. The methanol extract of Ardisia sieboldii exhibited promising inhibitory activity. Activity-guided fractionation of the methanol extract led to the isolation of five inhibitors 1〜5. Their structures have been elucidated on the basis of spectral data and chemical degradation. Active principles 1 and 2 have been identified as ardisiaquinones A and B, whereas 3〜5 have been unprecedented and thus named ardisiaquinones D, E and F, respectively. These simple dimeric structures with unique biological activity aroused our synthetic interest. Taking the nearly symmetrical structure of ardisiaquinones A(1) and D(3) into consideration, we have envisioned a key intermediate 8, which can be readily prepared by well-documented directed metallation. In practice, the commercially available 2,5-dimethoxy-p-benzoquinone 6 was converted quantitatively into the reduced form 7, which was lithiated with n-BuLi followed by alkylation with 1,7-dibromoheptane to give 8 in 73% yield. Lithium acetylide of 9 prepared from 8 was cross-coupled with 10 to give the requisite dimer 11 in 74% yield. Catalytic hydrogenation of the triple bond in 11 under Lindlar catalyst furnished the Z olefin 12. The hydroquinone obtained by deprotecting the MOM group in 12 was subjected to air oxidation to yield the p-benzoquinone 1a in 96% yield, which was converted into ardisiaquinone A(1) by selective demethylation. Synthesis of ardisiaquinone D (3) was also completed according to the similar procedure used for 1. Compound 14 was chosen as starting material, in this case, in order to accomplish the selective deprotection at the latter stage. Finally, relationship between structures and inhibitory activity of ardisiaquinones against 5-lipoxygenase is also discussed briefly.
天然有機化合物討論会の論文
1995-09-01

P-36 ヤブコウジ科植物モクタチバナより得られたArdisiaquinone類と5-リポキシゲナーゼ阻害活性(ポスター発表の部)

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