All posts by Núria

Discrimination of stereoisomers with RDCs

“Structural discrimination from in-situ measurement of 1DCH and 2DHH RDCs” by Núria Marcó,  R. R. Gil and Teodor Parella. Magnetic Resonance in Chemistry 2017, DOI: 10.1002/mrc.4575

A fast RDC-assisted strategy involving the simultaneous determination of scalar and total coupling constants from a single 1JCH/2JHH-resolved NMR spectrum is reported. It is shown that the concerted use of the directly measured 1DCH (for all CHn multiplicities) and 2DHH residual dipolar couplings allows an on-the-fly assignment of diastereotopic CH2 protons, as well as of an efficient discrimination between all eight possible diastereoisomeric structures of strychnine, which contains six stereocenters.

Pulse Programs Code for Bruker:

Data set Example:

Extraction of 1JCH for all carbon multiplicities.

“Perfect 1JCH-resolved HSQC: Efficient measurement of one-bond proton-carbon coupling constants along the indirect dimension” by Núria Marcó, A.A. Souza,  Pau Nolis, R. R. Gil and Teodor ParellaJournal of Magnetic resonance 2017, 276, 37-42. DOI: 10.1016/j.jmr.2017.01.002

A versatile 1JCH-resolved HSQC pulse scheme for the speedy, accurate and automated determination of one-bond proton-carbon coupling constants is reported. The implementation of a perfectBIRD element allows a straightforward measurement from the clean doublets obtained along the highly resolved F1 dimension, even for each individual 1JCHa and 1JCHb in diastereotopic HaCHb methylene groups. Real-time homodecoupling during acquisition and other alternatives to minimize accidental signal overlapping in overcrowded spectra are also discussed.

Pulse Programs Code for Bruker:

Data set Example:

New interface to visualize and determine 1JCH.

 1JCH NMR Profile: Identification of key structural features and functionalities by visual observation and direct measurement of one-bond proton-carbon coupling constants” by Núria Marcó, A.A. Souza,  Pau Nolis, Carlos Cobas, R. R. Gil and Teodor ParellaJournal of Organic Chemistry 2017, 276 : 37.42. DOI: 10.1021/acs.joc.6b02873 

A user-friendly NMR interface for the visual and accurate determination of experimental one-bond proton-carbon coupling constants (1JCH) in small molecules is presented. This intuitive 1JCH profile correlates directly delta(1H) and 1JCH facilitates the rapid identification and assignment of 1H signals belonging to key structural elements and functional groups. Illustrative examples are provided for some target molecules including terminal alkynes, strained rings, electronegative substituents or lone-pair bearing heteronuclei.

 

 

SeRMN at the SMASH NMR 2016 Conference

Some of our last research works has been presented at the annual meeting of the SmallMolecule NMR Conference (SMASH) that has been taken place in La Jolla (USA) from 11thto 14thSeptember 2016.

Teodor Parella presented two posters.
“In situ determination of 1DCH and 2DHH RDCs from a single 1JCH/2JHH -resolved NMR measurement” of Núria Marcó García, Roberto R. Gil and Teodor Parella.

Abstract: A fast RDC-assisted strategy involving the simultaneous determination of isotropic (scalar) and anisotropic (total) interactions is reported. The concerted use of individual 1DCH for all CHn multiplicities and 2DHH obtained from a single 1JCH/2JHH-resolved NMR spectrum offers an unambiguous assignment of diastereotopic protons and an efficient discrimination between all eight possible diastereoisomeric structures of strychnine which contains six stereocenters.

Figure: 500.13MHz JCH/JHH-Resolved spectra of 1 in A) isotropic CDCl3 and B) anisotropic PMMA-CDCl3 (2H nQ(CDCl3)=26 Hz) conditions. The projections along the F2 dimension are the conventional 1H spectrum in isotropic conditions and the 1H-CPMG spectrum in anisotropic conditions, respectively.

“Pure shift NMR covariance” of André Fredi, Pau Nolis, Carlos Cobas, Gary E. Martin, Teodor Parella.

Abstract: The development of novel experimental strategies to significantly enhance signal resolution by broadband homodecoupling is a current topic of high interest in 1H NMR spectroscopy . A number of different building blocks have been implemented into 1D and 2D homo- and heteronuclear experiments in order to provide resolution-enhanced pure chemical shift 1H NMR spectra, where signals appear collapsed to singlets. On the other hand, Covariance processing methods have been used to generate challenging NMR spectral representations . We present here the first attempts towards a general solution to generate Pure Shift NMR spectra by using Generalized Indirect Covariance (psGIC) co-processing3,4 . The current strategy is based on the calculation of a new 2D psGIC spectrum from the combination of a parent homo- or heteronuclear spectrum and a reference 2D F1-homodecoupled 1H- 1H correlation spectrum only showing diagonal cross-peaks (DIAG), which share a common 1H frequency dimension. Using psGIC, the F1 dimension in the DIAG spectrum is transferred to the F2 dimension of the parent spectrum, thus generating a new pure shift 2D spectrum

Figure: Generation of Pure Shift NMR spectra by using Generalized Indirect Covariance (psGIC)

Ultra high-resolution HSQC

SeRMN seminar

  • Date:  Thursday 7th May, 2015
  • Hour: 15:30
  • Location:  SeRMN,  Facultats de Ciències i Biociències, C2/-135
  • Speaker:  Núria Marcó, SeRMN PhD Student

The content of our recently published article entitled “Ultra high-resolution HSQC: Application to the efficient and accurate measurement of heteronuclear coupling constants” will be explained and discussed briefly. A rapid NMR data acquisition strategy in terms of enhanced resolution per time unit for the simple and efficient determination of multiple coupling constants is described. The use of 13C spectral aliasing combined with broadband 1H homodecoupling allows accurate measurements from ultra high resolved 2D HSQC cross-peaks.

Ultra HIgh Resolved HSQCportada

Ultra high-resolution HSQC: Application to the efficient and accurate measurement of heteronuclear coupling constants

Journal cover: Chemical Communications“Ultra high-resolution HSQC: Application to the efficient and accurate measurement of heteronuclear coupling constants” by Núria Marcó,  Andre Fredi and Teodor Parella. Chemical Communications 2015, 51:3262-3265. DOI: 10.1039/C4CC10279G

A rapid NMR data acquisition strategy in terms of enhanced resolution per time unit for the simple and efficient determination of multiple coupling constants is described. The use of 13C spectral aliasing combined with broadband 1H homodecoupling allows accurate measurements from ultra high resolved 2D HSQC cross-peaks.imagen4

 

Pulse Program Code for Bruker:

Data set Example: