52 エゾトリカブトの新塩基成分並びに主塩基ChasmanineからIsodelphonineの合成

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Three new minor diterpene alkaloids, ezochasmanine 12, ezochasmaconitine 9 and anisoezochasmaconitine 10 together with major alkaloids pseudkobusine 2 and chasmanine 8 were isolated from Aconitum yesoense Nakai. (Chart 1). The structures of new bases 12, 9 and 10 have been established as 3-α-hydroxychasmanine, 14-acetyl-8-benzoylchasmanine and 14-acetyl-8-anisoylchasmanine respectively. The structure of ezochasmanine 12 was first postulated from it's ^<13>CNMR spectrum and ^1HNMR spectrum of the 3-acetyl derivative. To confirm the structure, transformation of ezochasmanine 12 to chasmanine 8 of known structure was carried out as shown in chart 3. Ezochasmaconitine 9 and anisoezochasmaconitine 10 were synthesized from chasmanine 8 by two steps via. acetylation, benzoylation or p-anisoylation. These two alkaloids are the first examples of the diterpene alkaloids possessing the aroyl groups at C8 and acetyl group at C14. All of the formerly known congeners have the aroyl groups at C14 and acetyl group at C8. Mild toxicity was observed for the two new bases, 9 and 10. Isodelphonine 33 which is an alkamine of isodelphinine 34, was stereoselectively synthesized from chasmanine 8 as described below. (Chart 4). Oxidation of diacetylchasmanine 27 with KMnO_4 in aqacetone gave the des-N-ethyl derivative 28, which was then formylated to give N-formyl compound 29. Pyrolysis of 29 gave the Δ^<8,15> olefinic derivative 30, which was converted into epoxy derivative 31 by m-CPBA oxidation. Ring opening reaction of 31 using formic acid gave rise to the trans diol derivative 32 which was reduced by LiAlH_4 to yield isodelphonine, mp 135-137°, 33.
天然有機化合物討論会の論文
1980-09-10

52 エゾトリカブトの新塩基成分並びに主塩基ChasmanineからIsodelphonineの合成

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