Absolute configuration of chirally deuterated neopentane
Absolute configuration of chirally deuterated neopentane
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DOI：
10.1038/nature05653
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发表时间：
2007-03-29
期刊：
影响因子：
64.8
通讯作者：
Hug, W.
中科院分区：
文献类型：
--
作者：
Haesler, J.;Schindelholz, I.;Hug, W.
宏观手性和手性在分子水平上的关系是1951年通过异常x射线散射明确确立的(1)。虽然这项技术成为确定分子绝对构型的权威方法，但该方法的一个重要限制是分子必须包含“重”原子（例如，溴）。最近，通过测量分子的振动光学活性，可以直接确定更大范围分子的绝对构型（2,3）。在这里，我们展示了拉曼光学活性（4,5）的仪器进步，结合量子化学计算（6-8），使得确定(R)-[H-2(1), H-2(2), H-2(3)]-新戊烷(9)的绝对构型成为可能。这种饱和烃代表了由于质量分布不对称而具有手性的所有分子的原型。它在化学上是惰性的，不能衍生出能显示母体化合物绝对构型的分子。与其他分子的非对映体相互作用、旋光性和电子圆二色性，与众所周知的溴氯氟甲烷（10-12）的情况相反，预计无法测量。真空紫外线圆二色性中的振动效应可能会揭示分子的手性，但九个旋转体的存在将使光谱的解释变得极其困难，因为旋转体的核的空间排列与对映体相似。因此，对(R)-[H-2(1), H-2(2), H-2(3)]-新戊烷绝对构型的明确光谱测定提出了一个重大挑战，一个在可能的极限上的挑战。
The relationship between macroscopic chirality and chirality on the molecular level was unequivocally established in 1951 through anomalous X-ray scattering(1). Although this technique became the definitive method for determining the absolute configuration of a molecule, one important limitation of the approach is that the molecule must contain 'heavy' atoms ( for example, bromine). The direct determination of absolute configurations for a wider range of molecules has recently become possible by measuring a molecule's vibrational optical activity(2,3). Here we show that instrumental advances in Raman optical activity(4,5), combined with quantum chemical computations(6-8), make it possible to determine the absolute configuration of ( R)-[H-2(1), H-2(2), H-2(3)]-neopentane(9). This saturated hydrocarbon represents the archetype of all molecules that are chiral as a result of a dissymmetric mass distribution. It is chemically inert and cannot be derivatized to yield molecules that would reveal the absolute configuration of the parent compound. Diastereomeric interactions with other molecules, optical rotation, and electronic circular dichroism are, in contrast to the well-known case of bromochlorofluoromethane(10-12), not expected to be measurable. Vibronic effects in the vacuum ultraviolet circular dichroism might reveal that the molecule is chiral, but the presence of nine rotamers would make it extremely difficult to interpret the spectra, because the spatial arrangement of the rotamers' nuclei resembles that of enantiomers. The unequivocal spectroscopic determination of the absolute configuration of ( R)-[H-2(1), H-2(2), H-2(3)]-neopentane therefore presented a major challenge, one that was at the very limit of what is possible.