A robust alternative to η refinement for assessing the hand of chiral compounds
A robust alternative to η refinement for assessing the hand of chiral compounds
复制标题
用于评估手性化合物手性的 η 精修的稳健替代方案
DOI：
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
G. Gainsford
中科院分区：
文献类型：
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作者：
Y. Page;E. Gabe;G. Gainsford
通过对所有反射的手性参数进行最小二乘改进来评估手性分子化合物的手性，在统计上并不可靠，并且由于单个、未被注意到的总强度测量误差，可能导致不正确的答案。本文描述了另一种方法，其中最容易观察到的比吉沃特差是由解出的结构推导出来的，并在慢速和可能更长的波长下重新测量。利用适当的实验技术，可以消除吸收、多次反射和各向异性消光引起的测量误差。对得出错误手的概率的估计，完全基于重新测量的次数和矛盾的次数，因此对个别测量误差不敏感。根据这一估计，用Cu - Ktr强度数据来确定含氧为最重散射体的化合物的手性在统计上是明确的，甚至用Mo - Ka数据也是可行的。因此，该方法可以应用于以碳为最重散射体的分子的Cu Ka数据。这种方法已经在NRCVAX程序系统中作为实用程序BIVOET实现了自动化。
Assessment of the hand of chiral molecular compounds by least-squares refinement of a chirality parameter with all reflections is not statistically robust and can lead to incorrect answers due to a single, unnoticed, gross intensity-measurement error. An alternative is described in which the most easily observable Bijvoet differences are derived from the solved structure and remeasured at slow speed and possibly longer wavelength. Errors due to absorption, multiple reflections and anisotropic extinction can be cancelled out in the measurement for the sense of Bijvoet pairs with the proper experimental technique. An estimate of the probability of having derived the wrong hand, based exclusively on the number of remeasurements and the number of contradictions, and therefore insensitive to individual measurement errors, is developed. With this estimate, determination of the hand of compounds with oxygen as the heaviest scatterer is statistically unambiguous with Cu Ktr intensity data, and feasible even with Mo Ka data. Consequently, the method can be applied to Cu Ka data for molecules with carbon as the heaviest scatterer. This approach has been been automated as the utility BIVOET in the NRCVAX system of programs.