Ultraselective, Ultrahigh Resolution 1D TOCSY

Solution state 1H NMR spectroscopy provides valuable insights into molecular structure and conformation. However, when the spectrum exhibits severe signal overlap, it hampers the extraction of key structural information. Here, an ultraselective, ultrahigh resolution TOCSY method is introduced that greatly reduces spectral complexity, allowing the extraction of previously inaccessible spectral information. It combines the recently developed GEMSTONE excitation with homonuclear decoupling to provide highly simplified through-bond correlation 1D 1H NMR spectra, showing all signals within the selected spin system as singlets. The new method can greatly facilitate the analysis of mixtures, as shown here for a mixture of Cinchona alkaloids (popular catalysts in asymmetric synthesis) and a mixture of glucocorticoids (used for treating conditions such as asthma)

Improving the Sensitivity of FESTA Methods for the Analysis of Fluorinated Mixtures

Bruker pulse program codes and experimental data for MODO- and SRI-FESTA methods for the analysis of mixtures of 19F-containing species. ************************* EXPERIMENTAL DATA **************************************** Experimental data can be found here: \data\MODO-FESTA\nmr The experimental data provided here are those used and described in the main text and supporting information of the accompanying publication. Sample: mixture containing 1-chloro-1,1-difluoropentan-2-ol, dexamethasone, 2-fluorophenol, 3-fluorophenol and 4-fluorophenol in 0.7 mL of DMSO-d6. - Figure2 a) Experiment 1 - 1D 19F{1H} NMR of the mixture b) Experiment 2 - 1D 1H{19F} NMR of the mixture c) Experiment 3 - 1D 1H{19F} MODO-FESTA of 1-chloro-1,1-difluoropentan-2-ol d) Experiment 4 - 1D 1H{19F} MODO-FESTA of dexamethasone (H8) e) Experiment 5 - 1D 1H{19F} MODO-FESTA of dexamethasone (H11) f) Experiment 6 - 1D 1H{19F} MODO-FESTA of 2-fluorophenol g) Experiment 7 - 1D 1H{19F} MODO-FESTA of 3-fluorophenol h) Experiment 8 - 1D 1H{19F} MODO-FESTA of 4-fluorophenol - Figure3 a) Experiment 1 - 1D 19F{1H} NMR of the mixture b) Experiment 2 - 1D 1H{19F} NMR of the mixture c) Experiment 3 - 1D 1H{19F} MODO-FESTA of 1-chloro-1,1-difluoropentan-2-ol (1H selective pulse 11.66 ms) d) Experiment 4 - 1D 1H{19F} SRI-FESTA of 1-chloro-1,1-difluoropentan-2-ol (1H selective pulse 11.66 ms) e) Experiment 5 - 1D 1H{19F} MODO-FESTA of 1-chloro-1,1-difluoropentan-2-ol (1H selective pulse 2.33 ms) f) Experiment 6 - 1D 1H{19F} SRI-FESTA of 1-chloro-1,1-difluoropentan-2-ol (1H selective pulse 2.33 ms) - Figure4 a) Experiment 1 - 1D 19F{1H} NMR of the mixture b) Experiment 2 - 1D 1H{19F} NMR of the mixture c) Experiment 3 - 1D 1H{19F} MODO-FESTA of dexamethasone (H8) d) Experiment 4 - 1D 1H{19F} SRI-FESTA of dexamethasone (H8) - FigureS2 a) Experiment 1 - 1D 19F{1H} NMR of the mixture b) Experiment 2 - 1D 1H NMR of the mixture c) Experiment 3 - 1D 1H NMR of 1-chloro-1,1-difluoropentan-2-ol d) Experiment 4 - 1D 1H NMR of dexamethasone e) Experiment 5 - 1D 1H NMR of 2-fluorophenol f) Experiment 6 - 1D 1H NMR of 3-fluorophenol g) Experiment 7 - 1D 1H NMR of 4-fluorophenol ******************************************** PULSE PROGRAM CODES ******************************************** Bruker pulse program codes can be found here: \data\pp 1) MODO-FESTA_QNP (suitable for QNP probe) 2) SRI-FESTA_QNP (suitable for QNP probe) ============================================================================================================

Improving the sensitivity of FESTA methods for the analysis of fluorinated mixtures

The analysis of complex mixtures is an important but often intractable problem. When species contain sparse fluorine atoms, NMR spectra of fluorine-containing spin systems can be efficiently extracted from an intact mixture using the recently proposed FESTA (Fluorine-Edited Selective TOCSY Acquisition) methodology. Here an alternative approach to the existing selective reverse INEPT FESTA (SRI-FESTA) experiment is described, based on the use of a modulated spin echo for the initial excitation. MODO-FESTA (modulated echo FESTA) is simpler and has a significant sensitivity advantage over SRI-FESTA. Comparisons are presented of the relative sensitivity and spectral purity of the two types of methods92222242228CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPsem informação88881.030355/2013-012015/08541-6; 2016/24109-0; 2014/12776-6; 2015/19229-

On the anomalous temperature dependence of cellulose aqueous solubility

The solubility of cellulose in water-based media is promoted by low temperature, which may appear counter-intuitive. An explanation to this phenomenon has been proposed that is based on a temperature-dependent orientation of the hydroxymethyl group. In this paper, this hypothesis is investigated using molecular dynamics computer simulations and NMR spectroscopy, and is discussed in conjunction with alternative explanations based on solvent–solute and solvent–solvent hydrogen bond formation respectively. It is shown that neither simulations nor experiments lend support to the proposed mechanism based on the hydroxymethyl orientation, whereas the two alternative explanations give rise to two distinct contributions to the hydration free energy of cellooligomers