55(P-29) 血管新生阻害剤Epoxyquinol A,Bの酸化的二量化反応に関する研究(ポスター発表の部)

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We have reported the total synthesis of epoxyquinols A and B by the biomimetic oxidative dimerization. In order to reveal the reaction mechanism of the key oxidative dimerization, involving the three successive steps of oxidation, 6π-electrocyclization and Diels-Alder reaction, we have experimentally and theoretically investigated for the three 2-alkenyl-3-hydroxymethyl-2-cyclohexen-1-one derivatives such as epoxyquinol 3, epoxyquinone 9 and cyclohexenone 13. Of the sixteen possible modes of the oxidation/6π-electrocylization/Diels-Alder reaction cascade for the epoxy-quinone 9, and eight for the cyclohexenone 13, only the endo-anti(epoxide)-anti(Me)-hetero and endo-anti(Me)-hetero are respectively observed, while both endo-anti(epoxide)-anti(Me)-hetero and exo-anti(epoxide)-anti(Me)-homo reaction modes occur with the epoxyquinol 3. Calculation reveals that the transition state energy of observed reaction mode is the lowest, which is good agreement with the experimental results. While both epoxyquinone 9 and cyclohexenone 13 gave selectively only the epoxyquinol A-type products, the endo adducts, which are favored by the Woodward-Hoffman rule, both epoxyquinols A and B were obseaved in the case of the oxidative dimerization of 3. Calculation suggests that there is an intermolecular hydrogen-bonding stabilization at the transition state in the oxidative dimerization of 3, which affords epoxyquinol B, the exo Diels-Alder adduct. Intermolecular hydrogen-bonding interaction is also experimentally suggested by the observed solvent effect. That is, in the case of 3, the reaction proceeds faster in benzene and toluene than in MeOH, while MeOH is the suitable solvent in the case of 14.
天然有機化合物討論会の論文
2004-10-01

55(P-29) 血管新生阻害剤Epoxyquinol A,Bの酸化的二量化反応に関する研究(ポスター発表の部)

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