从单键 CC 偶合的 NMR 结构特征：一个缺氢的地衣酮的完全归属。

NMR structural characterization from one-bond C C couplings: Complete assignment of a hydrogen-poor depsidone.

机构信息

Department of Chemistry, University of Central Florida, Orlando, FL, USA.

Department of Chemistry, Utah Valley University, Orem, UT, USA.

出版信息

Magn Reson Chem. 2021 Jan;59(1):23-33. doi: 10.1002/mrc.5077. Epub 2020 Aug 3.

DOI:10.1002/mrc.5077

PMID:32687644

Abstract

The connectivity, conformation, tautomeric form, and dynamics of a new depsidone (perisalazinic acid) were characterized using one-bond C C NMR scalar couplings ( J ) obtained from the INADEQUATE experiment. Characterization of perisalazinic acid using more conventional NMR techniques is problematic due to the extremely limited number of CH protons present. In the present study, 81 candidate structures were considered and a best fit structure was selected by comparing computed J values for each candidate to 15 experimental values. Of the six flexible moieties in perisalazinic acid, three are adequately represented by a single orientation stabilized by intramolecular hydrogen bonding. The three remaining groups are present as mixtures of conformers with two sites consisting of a pair of conformations and another disordered over six orientations. This study demonstrates the feasibility of complete three-dimensional structural characterization of an unknown using only theoretical and experimental J values.

摘要

使用从 INADEQUATE 实验获得的单键 CC NMR 标量耦合（ J ），对一种新的地衣酸（佩利沙林酸）的连接、构象、互变异构形式和动态进行了表征。由于存在的 CH 质子数量极其有限，使用更常规的 NMR 技术对佩利沙林酸进行表征存在问题。在本研究中，考虑了 81 个候选结构，并通过将每个候选结构的计算 J 值与 15 个实验值进行比较，选择了最佳拟合结构。在佩利沙林酸的六个灵活部分中，有三个由单个构象稳定，通过分子内氢键稳定。其余三个部分以构象混合物的形式存在，其中两个位点由一对构象组成，另一个则无序分布在六个方向上。这项研究证明了仅使用理论和实验 J 值即可对未知物进行完整的三维结构表征的可行性。