HIGH-FIELD FT NMR APPLICATION OF MOSHER METHOD - THE ABSOLUTE-CONFIGURATIONS OF MARINE TERPENOIDS
HIGH-FIELD FT NMR APPLICATION OF MOSHER METHOD - THE ABSOLUTE-CONFIGURATIONS OF MARINE TERPENOIDS
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DOI：
10.1021/ja00011a006
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发表时间：
1991-05-22
影响因子：
15
通讯作者：
KAKISAWA, H
中科院分区：
文献类型：
--
作者：
OHTANI, I;KUSUMI, T;KAKISAWA, H
Mosher的（H-1）的方法来阐明仲醇的绝对构型重新检查通过使用高场FT NMR光谱，这使得分配复杂分子的大部分质子。 对于（-）-薄荷醇、（-）-薄荷醇、胆固醇和麦角甾醇的（R）-和（S）-MTPA酯，其绝对构型是已知的，得到的Δ-δ（Δ-S-Δ-R）值有系统的排列。 对这些化合物的Δ-Δ值的分析得出了一个可以预测天然产物绝对构型的规则。 将该规则应用于西松内酯和xenicane等海洋萜类化合物，对其绝对构型进行了归属，部分结果得到了X射线结构分析的证实。 在具有空间位阻OH基团的sipholenol A的情况下，该规则不适用。 但是，通过将OH基团反转到空间位阻较小的位置，这个问题得以克服;所得差向异构体给出了系统排列的Δ-Δ值，这使得能够阐明绝对构型。 与Mosher的F-19法比较表明，后者使用F-19 NMR缺乏可靠性。
Mosher's (H-1) method to elucidate the absolute configuration of secondary alcohols was reexamined by use of high-field FT NMR spectroscopy, which enables assignment of most of the protons of complex molecules. There is a systematic arrangement of DELTA-delta (delta-S - delta-R) values obtained for the (R)- and (S)-MTPA esters of (-)-menthol, (-)-borneol, cholesterol, and ergosterol, the absolute configurations of which are known. Analysis of the DELTA-delta values of these compounds led to a rule that could predict the absolute configurations of natural products. When this rule was applied to some marine terpenoids including cembranolides and xenicanes, their absolute configurations were assigned and a part of the results were confirmed by X-ray structural analyses. In the case of sipholenol A, which has a sterically hindered OH group, this rule is inapplicable. But the problem is overcome by inverting the OH group to a less sterically hindered position; the resulting epimer gives systematically arranged DELTA-delta values, which enabled the elucidation of the absolute configuration. Comparison of the present method with Mosher's F-19 method indicates that the latter one using F-19 NMR lacks in reliability.