Original and practical total syntheses of antitumor natural products

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We have synthesized epoxyquinol A, B, C and epoxytwinol A, by the biomimetic dimerization of 2H-pyran derivatives. The former three natural products were derived by the Diels-Alder reaction, while the latter was synthesized by the formal 4+4 cycloaddition reaction, which is a very rare reaction. We have investigated the reaction mechanism of this 4+4 cycloaddition via ab initio calculation and found that the reaction would proceed via a biradical mechanism. We have also synthesized several natural products with strong biological activities, such as lucilactaene, synerazol, pseurotin A, RK-805, fumagillol, FR65814, ovalicin, 5-demethylovalicin, EI-1941-1, EI-1941-2, EI-1941-3, panepophenanthrin, nikkomycin B, and fostriecin. During these syntheses, we developed several practical asymmetric reactions using oragnocatalysts such as direct aldol reaction in the presence of water, Mannich reaction, α-aminoxylation of carbonyl compounds, and Michael reaction.