Hellemann Erich, Gil Roberto R
Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave., Pittsburgh, PA, 15213, USA.
Chemistry. 2018 Mar 12;24(15):3689-3693. doi: 10.1002/chem.201704541. Epub 2018 Feb 16.
An existing gel stretching device is modified, permitting the use of organic solvents for the study of small molecules. Different from the original device, gels are stretched into 4 mm open-ended NMR tubes and then inserted into regular 5 mm NMR tubes. No open-ended tubes are inserted in the NMR probe avoiding the risk of sample leaking. It is also shown that residual chemical shift anisotropies (RCSAs) measured with the device are free of isotropic shift interferences and corrections for them are not needed during the post-acquisition data analysis. Three internal references for chemical shift were evaluated (CCl , CBr and TMS), being CCl the most convenient one to measure RCSAs in CDCl . RCSAs measured with the modified stretching device using CCl as the internal chemical shift reference were enough to determine the relative configuration of three small molecules with an excellent degree of configuration discrimination.
对现有的凝胶拉伸装置进行了改进，使其能够使用有机溶剂来研究小分子。与原始装置不同的是，凝胶被拉伸成4毫米开口端的核磁共振管，然后插入常规的5毫米核磁共振管中。没有开口端管插入核磁共振探头，避免了样品泄漏的风险。还表明，用该装置测量的残余化学位移各向异性（RCSA）没有各向同性位移干扰，在采集后数据分析过程中无需对其进行校正。评估了三种化学位移内标（CCl、CBr和TMS），其中CCl是在CDCl中测量RCSA最方便的一种。使用CCl作为内标化学位移参考，用改进的拉伸装置测量的RCSA足以确定三个小分子的相对构型，且构型区分度极佳。
