BIOSYNTHESIS OF ERGOT ALKALOIDS - STUDIES ON MECHANISM OF CONVERSION OF CHANOCLAVINE-I INTO TETRACYCLIC ERGOLINES
BIOSYNTHESIS OF ERGOT ALKALOIDS - STUDIES ON MECHANISM OF CONVERSION OF CHANOCLAVINE-I INTO TETRACYCLIC ERGOLINES
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DOI：
10.1021/ja00813a042
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发表时间：
1974-01-01
影响因子：
15
通讯作者：
CASSADY, JM
中科院分区：
文献类型：
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作者：
FLOSS, HG;TCHENGLI.M;CASSADY, JM
如用稳定同位素进行的双标记实验所示，裸花黄素-I环化为四环麦角林涉及C-9处的氢分子间转移到新分子的相同位置。同样在该方法中，前体的C-17处的亚甲基氢之一被交换，新引入的氢占据C-7处的pro-R位置。这一点以及麦角菌有效且特异性地将裸麦角碱-I-醛转化为麦角碱的事实表明环化涉及醛中间体。实验（37？，4 R）-甲羟戊酸-2-14 C-4-r酸的结果表明，在裸麦角碱-I的进一步代谢中的同位素效应导致未反应的裸麦角碱-I的C-9处的氚富集。一个机制，涉及双键异构化在醛阶段提出了所有的意见占。
As indicated by double labeling experiments with stable isotopes, the cyclization of chanoclavine-I to tetracyclic ergolines involves an intermolecular transfer of the hydrogen at C-9 into the same position of a new molecule. Also in this process, one of the methylene hydrogens at C-17 of the precursor is exchanged, the newly introduced hydrogen occupying the pro-R position at C-7. This and the fact that chanoclavine-I-aldehyde is efficiently and specifically converted into elymoclavine by the ergot fungus suggest that the cyclization involves aldehyde intermediates. Experiments with (37?, 4R)-mevalonic-2-14C-4-r acid indicate that an isotope effect in the further metabolism of chanoclavine-I leads to an enrichment of tritium at C-9 of the unreacted chanoclavine-I. A mechanism involving double bond isomerization at the aldehyde stage is proposed which accounts for all the observations.