14(B-10) Daphnicyclidin類および関連アルカロイドの環骨格多様性と推定生合成経路(口頭発表の部)

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Daphniphyllum alkaloids with unique heterocyclic ring systems are of current interest from a biogenetic point of view or as challenging targets for total synthesis. Recently, many Daphniphyllum alkaloids indicating the unique biogenetic path have been isolated. In our project on a search for biogenetic intermediates of Daphniphyllum alkaloids, a series of daphnicyclidins, daphmanidins, daphniglaucins, and calyciphyllines were isolated from the leaves, stems, and fruits of Daphniphyllum humile, D. teijsmanni, D. glaucescense, and D. calycinnum, together with a series of daphnezomines. The structures of these new alkaloids were elucidated on the basis of extensive 2D NMR techniques, X-ray analysis, CD spectra, and chemical derivatization. Daphnicyclidins A - H (1-8), J (9), and K (10) are novel types of alkaloids consisting of fused hexa- or penta-cyclic ring system, respectively. The biogenetic origin of daphnicyclidins seems to be yuzurimine-type alkaloids such as yuzurimine A and macrodaphniphyllamine with an appropriate leaving group at C-4. From biogenetic points of view, cleavage of C-1 - N-1 bond of daphniglaucin A (13) will give the skeleton of daphniglaucin D (16). Daphmanidins A (11) and B (12) might be generated from a common imine intermediate A. On the other hand, the biogenetic origin of daphniglaucin C (15) and calyciphylline B (18) seems to be an imine intermediate C, which might be produced through fragmentation reaction of the secodaphniphylline-type skeleton (B) derived from an imine intermediate A. Biogenetically, cleavage of C-6 - C-7 bond of an intermediate D will give the skeleton of daphniglaucin C (15). Calyciphylline B (18) might be generated from attack of the carboxyl group to C-5 of the intermediate C and cleavage of C-4 - C-5 and C-8 - C-9 bond followed by C-7 - C-9 bond formation. There are currently more than sixty Daphniphyllum alkaloids. This phytochemical developments in the structures of the new alkaloid types, such as the daphnezomines, the daphnicyclidins, the daphmanidins, the daphniglaucins, and the calyciphyllines will bring increasing structural variation to this alkaloid group. These unusual ring systems have attracted great interest as challenging targets for total synthesis or biosynthetic studies. Diversity of the ring skeletons in Daphniphyllum alkaloids might be related to the diversity of the biosynthetic pathways and the relevant enzymes. Widespread efforts for understanding the properties of these complex and fascinating alkaloids will result in further developments in this field.
天然有機化合物討論会の論文
2004-10-01

14(B-10) Daphnicyclidin類および関連アルカロイドの環骨格多様性と推定生合成経路(口頭発表の部)

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