期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 22, 期 16, 页码 5749-5755出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201505068
关键词
alkaloids; biosynthesis; conformation analysis; indoles; terpenoids
资金
- Fonds der chemischen Industrie
Experimental evidence is provided for the coherence of the double-bond geometry and the occurrence of secondary cyclizations in the biosynthesis of monoterpenoid indole alkaloids. Biosynthetically, akuammiline, C-mavacurine, and Strychnos alkaloids are proposed to be derived from the corynanthean alkaloid geissoschizine, a key intermediate in the biosynthetic pathway of these monoterpenoid indole alkaloids. This process occurs by so-called secondary cyclizations from geissoschizine or its derivatives. Although corynanthean alkaloids like geissoschizine incorporate E or Z double bonds located at C19-C20, the alkaloids downstream in the biosynthesis exclusively exhibit the E double bond. This study shows that secondary cyclizations preferentially occur with the E isomer of geissoschizine or its derivatives. This is attributed to the flexibility of the quinolizidine system of the corynanthean alkaloids, which can adopt a cis or trans conformation. For the secondary cyclization to take place, the cis-quinolizidine conformation is required. Experimental evidence supports the hypothesis that the E double bond of geissoschizine induces the cis conformation, whereas the Z double bond induces the trans conformation, which prohibits secondary cyclization of the Z compounds.
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