Long-Range Shielding Effects in the <sup>1</sup>H NMR Spectra of Mosher-like Ester Derivatives

Hoye, Thomas R.; Erickson, Sara E.; Erickson-Birkedahl, Sherrie; Hale, Christopher R. H.; Izgu, Enver Cagri; Mayer, Mathias; Notz, Patrick K; Renner, Matthew K.

doi:10.1021/ol1003862

Cited by 23 publications

(11 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this way, all of the signals of the protons in the two MPA esters of menthol were identified; their chemical shifts and the calculated Δδ RS are given in Table . The Δδ RS values are practically identical to those published by Hoye et al…”

Section: Resultssupporting

confidence: 87%

“…However, the acyl chloride cannot be used for MPA esters, because racemization occurs under these reaction conditions. MPA is to be preferred over MTPA because it yields larger Δδ RS ; however, the use of DCC obscures the signals in the aliphatic region as well. Careful weighing of the reagents in the reaction of MPA and decantation of the dicyclohexylurea (DCU) yield an NMR sample in which some signals of the alcohol moiety in the ester may be identified in the spectrum of the reaction mixture and used for analysis .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Selective Excitation 1D-NMR Experiments for the Assignment of the Absolute Configuration of Secondary Alcohols

Ghiviriga

2012

J. Org. Chem.

View full text Add to dashboard Cite

Routine selective excitation experiments, easy to set up on modern NMR spectrometers, allow for the determination of the absolute configuration of chiral secondary alcohols by double derivatization directly in the NMR tube. As a general method, TOCSY1D with selective excitation of the α proton in the MPA esters and with a short mixing time reveals only the nearby protons in the coupling network. Typically, the analysis takes less than 30 min. A longer mixing time, selective excitation of other signals, or NOESY1D experiments can be used for measuring ΔδRS of other protons.

show abstract

Section: Resultssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Selective Excitation 1D-NMR Experiments for the Assignment of the Absolute Configuration of Secondary Alcohols

Ghiviriga

2012

J. Org. Chem.

View full text Add to dashboard Cite

show abstract

“…Analogous observations can be made for para -substituted aromatic rings in proximity to chiral anisotropic groups. The relevance of small substituent chemical shift (scs) differences due to intramolecular long-range shielding effects across up to 15 bonds has recently been confirmed and further supports the significance of scs effects in the low Hz range.…”

Section: Case Studiesmentioning

confidence: 78%

Essential Parameters for Structural Analysis and Dereplication by ¹H NMR Spectroscopy

et al. 2014

View full text Add to dashboard Cite

The present study demonstrates the importance of adequate precision when reporting the δ and J parameters of frequency domain 1H NMR (HNMR) data. Using a variety of structural classes (terpenoids, phenolics, alkaloids) from different taxa (plants, cyanobacteria), this study develops rationales that explain the importance of enhanced precision in NMR spectroscopic analysis and rationalizes the need for reporting Δδ and ΔJ values at the 0.1–1 ppb and 10 mHz level, respectively. Spectral simulations paired with iteration are shown to be essential tools for complete spectral interpretation, adequate precision, and unambiguous HNMR-driven dereplication and metabolomic analysis. The broader applicability of the recommendation relates to the physicochemical properties of hydrogen (1H) and its ubiquity in organic molecules, making HNMR spectra an integral component of structure elucidation and verification. Regardless of origin or molecular weight, the HNMR spectrum of a compound can be very complex and encode a wealth of structural information that is often obscured by limited spectral dispersion and the occurrence of higher order effects. This altogether limits spectral interpretation, confines decoding of the underlying spin parameters, and explains the major challenge associated with the translation of HNMR spectra into tabulated information. On the other hand, the reproducibility of the spectral data set of any (new) chemical entity is essential for its structure elucidation and subsequent dereplication. Handling and documenting HNMR data with adequate precision is critical for establishing unequivocal links between chemical structure, analytical data, metabolomes, and biological activity. Using the full potential of HNMR spectra will facilitate the general reproducibility for future studies of bioactive chemicals, especially of compounds obtained from the diversity of terrestrial and marine organisms.

show abstract

“…In the present studies, the s ‐triazine‐based CDR has been successful in the determination of the absolute configuration of the diastereomers of ( RS )‐Bac because of the strong anisotropic shielding effect produced by it, resulting in a chemical shift difference (Δδ) between the two diastereomers; suitable CDRs and appropriate analysis of anisotropic shielding effect produced by them helps in the determination of the absolute configuration of the diastereomers. However, as per prevailing practice in the literature, determination of the absolute configuration of the enantiomers has been through X‐ray crystallography.…”

Section: Resultsmentioning

confidence: 89%

Preparative Enantioseparation of (RS)‐Baclofen: Determination of Molecular Dissymmetry

Vashistha

Bhushan

2015

Chirality

View full text Add to dashboard Cite

The present work reports preparative enantioseparation of (RS)-baclofen using thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). Diastereomers were synthesized using a new monochloro-s-triazine-based chiral derivatizing reagent (CDR), namely, N-(4-chloro-6-piperidinyl-[1,3,5]-triazine-2-yl)-L-phenylalanine, under microwave irradiation. Acetonitrile-0.1% aq. triflouroacetic acid in gradient elution mode and CH3 OH-CH2 Cl2 (4:5; v/v) were successful as mobile phase in HPLC and TLC, respectively. The two diastereomers were isolated by preparative TLC. Molecular dissymmetry was established by developing the lowest energy optimized structures of the diastereomers based on Density Functional Theory and with the help of (1) H NMR showing anisotropic effect associated with aromatic ring of s-triazine (in the CDR). The configuration of diastereomers was established as [L-Phe-(R)-Bac] and [L-Phe-(S)-Bac], where the first notation refers to the configuration of chiral auxiliary (of the CDR) and the second to that of the analyte Bac. Limits of detection were found to be 0.056 and 0.061 ng mL(-1), respectively, for the two diastereomers. Determination of absolute configuration of the two diastereomers lent support to the elution order and separation mechanism.

show abstract

Long-Range Shielding Effects in the ¹H NMR Spectra of Mosher-like Ester Derivatives

Cited by 23 publications

References 15 publications

Selective Excitation 1D-NMR Experiments for the Assignment of the Absolute Configuration of Secondary Alcohols

Selective Excitation 1D-NMR Experiments for the Assignment of the Absolute Configuration of Secondary Alcohols

Essential Parameters for Structural Analysis and Dereplication by ¹H NMR Spectroscopy

Preparative Enantioseparation of (RS)‐Baclofen: Determination of Molecular Dissymmetry

Contact Info

Product

Resources

About

Long-Range Shielding Effects in the 1H NMR Spectra of Mosher-like Ester Derivatives

Cited by 23 publications

References 15 publications

Selective Excitation 1D-NMR Experiments for the Assignment of the Absolute Configuration of Secondary Alcohols

Selective Excitation 1D-NMR Experiments for the Assignment of the Absolute Configuration of Secondary Alcohols

Essential Parameters for Structural Analysis and Dereplication by 1H NMR Spectroscopy

Preparative Enantioseparation of (RS)‐Baclofen: Determination of Molecular Dissymmetry

Contact Info

Product

Resources

About

Long-Range Shielding Effects in the ¹H NMR Spectra of Mosher-like Ester Derivatives

Essential Parameters for Structural Analysis and Dereplication by ¹H NMR Spectroscopy