A chiral axis due to an acyclic imide-Ar bond: a study of steric effects of acyl groups on racemization
A chiral axis due to an acyclic imide-Ar bond: a study of steric effects of acyl groups on racemization
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DOI：
10.1016/s0040-4020(00)00852-8
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发表时间：
2000-11-03
期刊：
影响因子：
2.1
通讯作者：
Murakami, Y
中科院分区：
文献类型：
--
作者：
Kondo, K;Iida, T;Murakami, Y
本文研究了一系列光学活性化合物3a-e的外消旋作用，包括酰基的空间位阻效应。已经报道了光学活性化合物3c和3d的第一个实例，其具有基于无环酰亚胺-Ar键的轴向手性。一个很有趣的结果已经被揭示，即，3a带有一个大的酰基，而不是一个相对较小的一个更容易外消旋。为了解释这种观察到的现象，进行了C-13 MMR实验和3a-e与苄胺的反应。这些结果表明，与对消旋相对稳定的RCO-N键相比，3a中的t-BuCO-N键更容易发生外消旋，而3b-e中的RCO-N键则更容易发生外消旋。此外，通过圆二色光谱确定了3b和3e的绝对构型为R，并对外消旋体3f进行了X-射线晶体学分析。(C)2000年由Elsevier Science Ltd.出版
Studies on the racemization in a series of optically active compounds 3a-e, including the steric effect of their acyl groups, are described. The first example of optically active compounds 3c and 3d, which possess axial chirality based on an acyclic imide-Ar bond, has been reported. A quite interesting result has been revealed, namely, that 3a bearing a bulky acyl group rather than a relatively small one racemized more easily. To explain this observed phenomenon, C-13 MMR experiments and the reaction with benzylamine of 3a-e were undertaken. These results suggested that the t-BuCO-N bond in 3a which racemized easily, is more twisted, compared with the RCO-N bonds in 3b-e which are relatively stable to racemization. Furthermore, the absolute configuration of 3b and 3e has been determined to be R by the CD spectrum and the X-ray crystallographic analysis of racemic 3f has been accomplished. (C) 2000 Published by Elsevier Science Ltd.