P-54 Erinacine類の不斉全合成研究(ポスター発表の部)

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Erinacines are diterpene-xylosides isolated from the cultured mycelia of Hericium erinaceum, possessing "cyathane skeleton", a novel common 5-6-7 tricyclic ring system with two streogenic quaternary carbon centers at the ring junctures. They exhibit potent stimulating activity for NGF-synthesis, and erinacine E also shows the selective κ-opioid recepter agonist activities. Since this family shows the structual novelties and unique biological activities, they have been attractive targets for total synthesis. Toward these syntheses, we have developed a convergent synthetic strategy involving two fragments derived from originally developed chiral building blocks. Fragment A was prepared in an optically pure form through the originally developed catalytic asymmetric intramolecular cyclopropanation of the α-diazo-β-keto sulfone. Fragment B was derived from the optically pure building block, which was newly prepared by the baker's yeast-mediated asymmetric reduction of the prochiral 1,3-cyclohexanedione. Through the key steps, that is, assembly of these two fragments, intramolecular aldol reaction to furnish the 5-6-6 tricyclic ring system, and ring expansion reaction generating the 5-6-7 ring system, the convergent asymmetric first total synthesis of (+)-allocyathin B_2, an aglycon of (+)-erinacine A, has been achieved. Erinacines except for (+)-erinacine A possess an additional stereogenic center at the B-C ring junctures, containing the trans-fused B-C ring. This stereogenic center was effectively elaborated via the SmI_2-mediated reduction of the α,β-unsaturated ketone using the C14 hydroxyl group as a proton source. For completion of the total synthesis of erinacines, further conversions including the glycosidation reaction have been investigated. The results obtained in this study will be presented.
天然有機化合物討論会の論文
2005-09-15

P-54 Erinacine類の不斉全合成研究(ポスター発表の部)

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