When not to rely on Boltzmann populations. Automated CASE-3D structure elucidation of hyacinthacines through chemical shift differences

When not to rely on Boltzmann populations. Automated CASE-3D structure elucidation of hyacinthacines through chemical shift differences

© 2019 John Wiley & Sons, Ltd.

Bibliographische Detailangaben
Veröffentlicht in:Magnetic resonance in chemistry : MRC. - 1985. - 58(2020), 2 vom: 07. Feb., Seite 139-144
1. Verfasser: Navarro-Vázquez, Armando (VerfasserIn)
Format: Online-Aufsatz
Sprache:English
Veröffentlicht: 2020
Zugriff auf das übergeordnete Werk:Magnetic resonance in chemistry : MRC
Schlagworte:Journal Article Research Support, Non-U.S. Gov't CASE DP4 GIAO Structural elucidation stereochemistry
Beschreibung
Zusammenfassung:© 2019 John Wiley & Sons, Ltd.
An Akaike Information Criterion (AIC) procedure (CASE-3D) has been successfully applied to the NMR based configurational assignment of reported hyacinthacines (1-3,5-8), recently target of configurational analysis using the popular DP4+ methodology. The present analysis makes use of reported 1 H and 13 C shifts and, in some particular cases, a few 3 JHH couplings. The difficulty in proper computational prediction of relative energies, in molecules capable of inter-molecular hydrogen bonding, introduces large errors in the prediction of conformationally averaged NMR properties in methods based on Boltzmann averaging such as DP4 or DP4+. In contrast CASE-3D conformational amplitudes are free parameters in the model. Here we show that the CASE-3D conformational model selection strategy, when combined with a larger energy cutoff in the molecular-modelling conformational exploration, was sufficient to correctly assign the relative configuration in five of seven cases. Introduction of more information, either by supplementing 1 H and 13 C data with a few J-couplings, or using a cutoff based on computed DFT energies for the definition of the conformational ensembles, allowed the safe assignment of configuration for all compounds
Beschreibung:Date Completed 27.01.2020
Date Revised 27.01.2020
published: Print-Electronic
Citation Status PubMed-not-MEDLINE
ISSN:1097-458X
DOI:10.1002/mrc.4951