Fomenting proton anisochronicity in the CH2D group
Fomenting proton anisochronicity in the CH2D group
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DOI：
10.1021/ja034242l
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发表时间：
2003-07-30
影响因子：
15
通讯作者：
O'Leary, DJ
中科院分区：
文献类型：
--
作者：
Allen, BD;O'Leary, DJ
一种新的C−D···N相互作用促进了平衡同位素效应，导致（N-CH 2D）-（−）-isosparteinium阳离子中非对映异构甲基质子的化学位移差异（43 ppb，22 °C）。观察到的化学位移差异是令人惊讶的协议与基于从头算协议的预测44 ppb。这些计算也显示出在Anet的α-氘代-1，2-二甲基哌啶（理论，17 ppb;实验，14 ppb）的实验位移差再现。本文所述的异天冬氨酸衍生系统可以提供用于通过氚NMR光谱法指定立体甲基（R-CHDT）的构型和对映体纯度的改进方法。
A novel C−D···N interaction promotes an equilibrium isotope effect that causes a large chemical shift difference (43 ppb, 22 °C) for the diastereotopic methyl protons in the (N-CH2D)-(−)-isosparteinium cation. The observed chemical shift difference is in surprising agreement with a prediction of 44 ppb based upon an ab initio protocol. These calculations are also shown to reproduce the experimental shift difference in Anet's α-deutero-1,2-dimethylpiperidine (theory, 17 ppb; experiment, 14 ppb). The isosparteine-derived system described herein may provide an improved method for assigning the configuration and enantiomeric purity of stereogenic methyl groups (R-CHDT) by tritium NMR spectroscopy.