48(P-15) ヒカゲノカズラ科植物Lycopodium serratum含有アルカロイド類に関する化学的研究(ポスター発表の部)

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The genus Lycopodium (Lycopodiaceae), which produces a potential therapeutic agent, huperzine A (1), for the treatment of Alzheimer 's disease, has been extensively studied in recent years, resulting in the isolation of a number of new alkaloids. We also succeeded in the isolation of several new alkaloids from the crude basic fraction of Lycopodium serratum Thunb. collected at Chiba prefecture. The structures of new alkaloids were elucidated by spectroscopic analyses and chemical correlations, as follows. A new alkaloid, lycoposerramine-A (2), was obtained as colorless needles (mp. 169-171℃, C_<18>H_<29>N_3O_2). The one- and two-dimensional NMR data enabled us to construct the basic skeleton of 2 possessing a fused tricyclic ring system with five- and six-membered cycloalkanes and a 1-azacyclononane, which retains the fundamental backbone of the known alkaloid, fawcettimine (3). The structure was finally established by X-ray crystallographic analysis. Lycoposerramine-A (2) is the first example of a natural product that contains a 1,2,4-oxadiazolidine-5-one residue in the molecule. The structure of second new alkaloid, lycoposerramine-B (4), was initially elucidated by spectroscopic data including the J-resolved HMBC spectra. The novel structure having a oxime function was confirmed by chemical transformation from a known alkaloid, serratinine (5), via an eight-steps operation, which included a reductive ring-opening of an α-immonium ketone group and a regioselective oximation as the key reactions. Lycoposerramine-C (14) was obtained as colorless prisms (mp. 164-165℃) and its structure possessing the fawcettimine-skeleton was determined by spectroscopic and X-ray analyses. It was found that treatment of 14 with NaOMe in MeOH afforded two known alkaloids, phlegmariurines A (15) and B (16). Other fawcettimine-related new alkaloids (20, 22-26) were isolated and these structures were inferred by spectroscopic analyses and/or chemical transformations. The biogenetic route of these new fawcettimine-related alkaloids starting from fawcettimine (3) was proposed. Ten new alkaloids (27, 29-37) having lycopodine-related structure were also isolated and their structures were elucidated on the basis of spectroscopic analyses and/or chemical transformations.
天然有機化合物討論会の論文
2004-10-01

48(P-15) ヒカゲノカズラ科植物Lycopodium serratum含有アルカロイド類に関する化学的研究(ポスター発表の部)

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