Stereochemical Aspects of<sup>13</sup>C NMR Spectroscopy

Wilson, Nancy K.; Stothers, J. B.

doi:10.1002/9780470147177.ch1

Cited by 84 publications

(5 citation statements)

References 229 publications

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“…All structures were optimized at the B3LYP − /6-311++G(d,p) − level by using the Gaussian 09 software package . A very similar basis set was described to be suitable to describe intramolecular interactions that are responsible for trends in 13 C chemical shifts .…”

Section: Computational Detailsmentioning

confidence: 99%

“…A variety of explanations has been given during the last 50 years. Archer et al referred to steric reasons, which were widely accepted in the further course, ,,,− but seem to be less stressed inbetween. Other explanations considered a presumed magnetic anisotropy of the S–O bond, as it is present in acetylenes. − ,,, Nevertheless, this anisotropy has never been investigated thoroughly.…”

Section: Introductionmentioning

confidence: 99%

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Stereoelectronic Effects: The γ-Gauche Effect in Sulfoxides

Jung

Podlech

2018

J. Phys. Chem. A

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Reasons for the C NMR γ-gauche effect in sulfoxides, i.e., the distinct shielding of a carbon β to a gauche-oriented sulfoxide group were investigated. Several calculated and measuredC NMR data of open chain or thiane-derived sulfoxides revealed that an upfield shift is only observed for that γ-gauche position, in which the respective carbon is anti to the sulfoxide's sulfur lone pair. Carbons in γ-gauche position, which are synclinal to the lone pair, are not affected. The magnetic anisotropy of the S═O group was examined by generation of iso-chemical-shielding surfaces (ICSSs) and magnetically induced current maps. Stereoelectronic interactions were determined with natural bond orbital (NBO) and natural chemical shielding (NCS) analyses. The γ-gauche effect is best described by stereoelectronic interactions, especially those of the sulfur's lone pair with antibonding orbitals to a β-carbon in antiperiplanar orientation. An explanation based on steric interactions, which has frequently been referred to, is not suitable to describe the observed shielding effects. Furthermore, a description of the bonding situation in the S═O group is given. It can be understood as S-O triple bond, where the bond order is significantly reduced by antibonding contributions in some of the occupied molecular orbitals.

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Section: Computational Detailsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Stereoelectronic Effects: The γ-Gauche Effect in Sulfoxides

Jung

Podlech

2018

J. Phys. Chem. A

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“…Heteronuclear NMR spectroscopy is essential for confirming the identity of peptide molecules such as stereochemistry with the involvement of D-amino acids. 16 This study serves to assign both 13 C and 15 N nuclei, alongside all aromatic protons for the D-Phe, Phe, and D-Trp residues in an aqueous environment for the octreotide acetate peptide using an array of 1-and 2-dimensional (1D and 2D) NMR techniques. The study focuses on 1D 1 H and 13 C techniques as well as 2D 1 H-1 H, 1 H- 13 C, and 1 H- 15 N chemical shift correlation spectra to provide better residue-specific spectral information.…”

Section: Introductionmentioning

confidence: 99%

“…Heteronuclear 13 C and 15 N NMR provide a greater disparity between resonances; combined with no spin–spin coupling between neighboring nuclei, these spectra provide additional opportunities to study differences in chemical structure. Heteronuclear NMR spectroscopy is essential for confirming the identity of peptide molecules such as stereochemistry with the involvement of D‐amino acids 16 . This study serves to assign both 13 C and 15 N nuclei, alongside all aromatic protons for the D‐Phe, Phe, and D‐Trp residues in an aqueous environment for the octreotide acetate peptide using an array of 1‐ and 2‐dimensional (1D and 2D) NMR techniques.…”

Section: Introductionmentioning

confidence: 99%

Multinuclear ¹H/¹³C/¹⁵N chemical shift assignment of therapeutic octreotide acetate performed at natural abundance

Menke,

Chen,

Chen

2024

Magnetic Reson in Chemistry

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Octreotide acetate, the active pharmaceutical ingredient in the long‐acting release (LAR) drug product Sandostatin®, is a cyclic octapeptide that mimics the naturally occurring somatostatin peptide hormone. Modern NMR can be a robust analytical method to identify and quantify octreotide molecules. Previous 1H chemical shift assignments were mostly performed in organic solvents, and no assignments for heteronuclear 13C, 15N, and aromatic 1H nuclei are available. Here, using state‐of‐the‐art 1D and 2D homo‐ and heteronuclear NMR experiments, octreotide was fully assigned, including water exchangeable amide protons, in aqueous buffer except for 13CO and 15NH of F1, 15NH of C2, and 15NζHζ of K5 that were not observed because of water exchange or conformational exchange. The solution NMR spectra were then directly compared with 1D 1H/13C/15N solid‐state NMR (SSNMR) spectra showing the potential applicability of 13C/15N SSNMR for octreotide drug product characterization.

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“…Stereochemical problems were increasingly being investigated by 13 C nuclear magnetic resonance techniques [1][2][3] . The chemical shift values constitute a very sensitive probe for conformational properties.…”

Section: Introductionmentioning

confidence: 99%

13C NMR Spectroscopy: A Tool for Study of Conformational Analysis of 2-Aryl-trans-decahydroquinolin-4-ols

Sharmila¹,

B²,

G.V.³

et al. 2019

CJST

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In this investigation, proton decoupled 13C NMR Spectroscopy was used as a tool for the study of conformations of differently substituted 2-aryl-trans-decahydroquinolin-4-ols. The fusion of the rings in 2-aryl-trans-decahydroquinolin-4-ols was conclusively proved to be trans-, from a comparison of the experimental and calculated values. The signal assignments were made on the basis of the model system and in this case trans-decahydroquinoline was taken as model system. Substituent parameters for methyl, hydroxyl, and phenyl groups were derived from analogous systems and incorporated in the model system to obtain the calculated values. An examination of the 13C chemical shift values indicated that the configuration of the hydroxyl group was equatorial in all the α-forms of 2-aryl-trans-decahydroquinolin-4-ols and that of β-form’s was axial. In 3-Methyl-2-aryl-trans-decahydroquinolin-4-ols the chemical shifts suggested equatorial configuration to methyl and phenyl groups. Further, for 1-Methyl-2-aryl-trans-decahydroquinolin-4-ol and 1,3-dimethyl-2-aryl-trans-decahydroquinolin-4-ols the 1-or N-methyl group was found to has a greater preference to the equatorial position.

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Stereochemical Aspects of¹³C NMR Spectroscopy

Cited by 84 publications

References 229 publications

Stereoelectronic Effects: The γ-Gauche Effect in Sulfoxides

Stereoelectronic Effects: The γ-Gauche Effect in Sulfoxides

Multinuclear ¹H/¹³C/¹⁵N chemical shift assignment of therapeutic octreotide acetate performed at natural abundance

13C NMR Spectroscopy: A Tool for Study of Conformational Analysis of 2-Aryl-trans-decahydroquinolin-4-ols

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Stereochemical Aspects of13C NMR Spectroscopy

Cited by 84 publications

References 229 publications

Stereoelectronic Effects: The γ-Gauche Effect in Sulfoxides

Stereoelectronic Effects: The γ-Gauche Effect in Sulfoxides

Multinuclear 1H/13C/15N chemical shift assignment of therapeutic octreotide acetate performed at natural abundance

13C NMR Spectroscopy: A Tool for Study of Conformational Analysis of 2-Aryl-trans-decahydroquinolin-4-ols

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Stereochemical Aspects of¹³C NMR Spectroscopy

Multinuclear ¹H/¹³C/¹⁵N chemical shift assignment of therapeutic octreotide acetate performed at natural abundance