124(P-64) 分子間エンインメタセシスを利用したBulnesolの合成研究(ポスター発表の部)
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We have already reported the novel synthesis of 1,3-diene from alkyne and ethylene using ruthenium-catalyzed intermolecular enyne metathesis. A CH_2Cl_2 solution of alkyne and a catalytic amount of ruthenium catalyst 1 was stirred under ethylene gas (1 atm) at room temperature to give 1,3-diene in high yield. We planed for the synthesis of natural product, bulnesol 5, using this novel 1,3-diene synthesis. When a CH_2Cl_2 solution of alkyne 7 and 1 (3mol %) was stirred under ethylene gas at room temperature for 45h, 1,3-diene 8 was obtained in only 10% yield along with 7 in 58% yield. The yield was improved to 80%, when alkyne 13c having an acetoxy group at a propargylic position was used for this reaction. Intramolecular Dield-Alder reaction of 14a proceeded smoothly to produce 15a, which was treated with O_3 and then PPTS to give compounds 16a and 17a having bicyclo[5.3.0]decenone skeleton in 84% yield according to the Shea's report. On the basis of these results, we attempted to synthesize of bulnesol 5. When a CH_2Cl_2 solution of compound 24 and 10mol % of 1 was stirred under ethylene gas at room temperature for 20h, 1,3-diene 25 was obtained in quantitative yield. Diels-Alder reaction followed by decarboxylation and then deacetoxylation gave 30. Ozonolysis of 30 followed by treatment with K_2CO_3 in MeOH afforded α,β-unsaturated ketone 32, which was hydrogenated with 10% Pd on charcoal to provide compound 35. Now we tried to convert compound 35 into bulnesol 5.
- 天然有機化合物討論会の論文
- 2000-10-01