71(P-59) エゾユズリハDaphniphyllum humileより単離した新規アルカロイドDaphnezomine A-Kの構造(ポスター発表の部)

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Daphniphyllum alkaloids are a group of highly complex polycyclic alkaloids which have attracted great interest from a biogenetic point of view. These stimulating polycyclic skeletons have prompted extensive synthetic work. Heathcock and co-workers have demonstrated a one-pot synthesis of a dialdehyde to a pentacyclic unsaturated amine, which turned out to be an exceptionally efficient way to construct the pentacyclic nucleus of the Daphniphyllum alkaloids, based on the hypothesis of their biosynthesis. In our project on a search for biogenetic intermediates of Daphniphyllum alkaloids, daphnezomines A (1) and B (2), novel alkaloids possessing an aza-adamantane core containing an amino ketal bridge, daphnezomines F (6) and G (7), those possessing 1-azabicyclo[5.2.2]undecane ring system, and daphnezomines C〜E (3〜5) and H〜K (8〜11) were isolated from the leaves, stems, and fruits of Daphniphyllum humile. The structures of 1 and 2 were elucidated on the basis of extensive 2D NMR techniques, X-ray analysis, and chemical derivatization. The structures of 6 and 7 were assigned by combination of 2D NMR methods at various temperatures and computational techniques. Daphnezomines A (1) and B (2) consisting of all six-membered rings are the first natural products containing an aza-adamantane core with an amino ketal bridge, which may be generated from a nitrogen-involved squalene intermediate via secodaphniphylline skeleton. Daphnezomines A (1) and B (2) might be generated through ring expansion accompanying backbone rearrangement of a common fragmentation intermediate. Daphnezomines F (6) and G (7) are novel alkaloids containing the 1-azabicyclo[5.2.2]undecane ring system. The structures of 6 and 7 are similar to that of yuzurimine but they lack the C-1-C-2 bond. Daphnezomine G (7) might be generated through oxidation of a common imine intermediate and subsequent cleavage of the C-7-C-10 bond followed by formation of the C-19-N-1 and C-14-C-15 bonds to give daphnezomine G (7). Daphnezomine F (6) may be derived from daphnezomine G (7) through oxidation of the C-7-C-6 bond.
天然有機化合物討論会の論文
2000-10-01

71(P-59) エゾユズリハDaphniphyllum humileより単離した新規アルカロイドDaphnezomine A-Kの構造(ポスター発表の部)

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