Quiquempoix Lucas, Bogdan Elena, Wells Neil J, Le Questel Jean-Yves, Graton Jérôme, Linclau Bruno
Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
CEISAM UMR CNRS 6230, Faculté des Sciences et des Techniques, Université de Nantes, 2 rue de la Houssinière-BP 92208, 44322 Nantes CEDEX 3, France.
Molecules. 2017 Mar 24;22(4):518. doi: 10.3390/molecules22040518.
Organofluorine is a weak hydrogen-bond (HB) acceptor. Bernet et al. have demonstrated its capability to perturb OH···O intramolecular hydrogen bonds (IMHBs), using conformationally rigid carbohydrate scaffolds including levoglucosan derivatives. These investigations are supplemented here by experimental and theoretical studies involving six new levoglucosan derivatives, and complement the findings of Bernet et al. However, it is shown that conformational analysis is instrumental in interpreting the experimental data, due to the occurrence of non-intramolecular hydrogen-bonded populations which, although minor, cannot be neglected and appears surprisingly significant. The DFT conformational analysis, together with the computation of NMR parameters (coupling constants and chemical shifts) and wavefunction analyses (AIM, NBO), provides a full picture. Thus, for all compounds, the most stabilized structures show the OH groups in a conformation allowing IMHB with O5 and O6, when possible. Furthermore, the combined approach points out the occurrence of various IMHBs and the effect of the chemical modulations on their features. Thus, two-center or three-center IMHB interactions are observed in these compounds, depending on the presence or absence of additional HB acceptors, such as methoxy or fluorine.
有机氟是一种弱氢键（HB）受体。伯内特等人利用包括左旋葡聚糖衍生物在内的构象刚性碳水化合物支架，证明了其干扰OH···O分子内氢键（IMHBs）的能力。本文通过涉及六种新的左旋葡聚糖衍生物的实验和理论研究对这些研究进行了补充，并补充了伯内特等人的研究结果。然而，结果表明，由于存在非分子内氢键结合的群体，尽管数量较少但不能忽视且显得出人意料地显著，构象分析有助于解释实验数据。DFT构象分析，连同NMR参数（耦合常数和化学位移）的计算以及波函数分析（AIM、NBO），提供了一个全面的情况。因此，对于所有化合物，最稳定的结构在可能的情况下显示出OH基团处于一种能与O5和O6形成IMHB的构象。此外，综合方法指出了各种IMHB的存在以及化学调制对其特征的影响。因此，在这些化合物中观察到了双中心或三中心IMHB相互作用，这取决于是否存在额外的HB受体，如甲氧基或氟。
