1H, 13C and 19F NMR spectral data for fifteen fluorinated steroids

Nelson, Janis T.; Kurz, Lilia J.

doi:10.1002/mrc.1260310210

Cited by 6 publications

References 9 publications

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Fluorine as an NMR probe for structural studies of chemical and biological systems

2000

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Applications of fluorine NMR to probe long‐range interactions in rigid organic molecules, namely cubanes, and to study structures and dynamics of proteins and other biological systems, are presented. 19F NMR parameters, especially long‐range coupling constants are shown to reveal intrinsic features of the molecules. Correlations between long‐range (more than three‐bond) couplings involving fluorine and other chemical and physico‐chemical properties of the compounds are demonstrated, and examples of unusual couplings which cannot be explained by existing theories of ‘through‐bond’ and ‘through‐space’ mechanisms are discussed. Recent applications of fluorine labeling of aromatic and aliphatic amino acids in investigating protein structures and dynamics are highlighted. The potential of using 19F NMR parameters, such as large spin–spin coupling constants observed for organic compounds, for structural analysis of biological macromolecules is outlined. Copyright © 2000 John Wiley & Sons, Ltd.

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Fluorine as an NMR probe for structural studies of chemical and biological systems

2000

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3‐Fluoropiperidines and N‐Methyl‐3‐fluoropiperidinium Salts: The Persistence of Axial Fluorine

Sun

Lankin

Hardcastle

et al. 2005

Chemistry A European J

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It has previously been shown that the fluorine atom in N-protonated 3-fluoropiperidine salts in water strongly prefers the axial orientation in the six-membered ring chairs. In the present work we examine the proposition that the N-methyl salts are equally disposed to present axial fluorine. Initially, we explored this point by comparing the structures of the corresponding NH2+, NHMe+, and NMe2+ salts by means of density functional theory (DFT), ab initio, and MMFF force field calculations with and without aqueous solvation models. The predictions unambiguously pointed to axial fluorine for all salts investigated, including those with simultaneous axial F and (N)Me. The calculations were followed by synthesis of the corresponding series of 4,4-diphenylpiperidinium salts. These were evaluated by one- and two-dimensional NMR spectroscopy in [D6]DMSO to fully corroborate the axial disposition of the fluorine in each of the compounds. X-ray crystal structure determinations were likewise performed for the diphenyl-3-fluoro NH2+ and NMe2+ systems to substantiate axial-F. Comparison of the X-ray structures of the fluorinated and unfluorinated NMe2+ salts reveals that the fluorine resides axial in spite of substantial steric compression. While the charge-dipole phenomenon responsible for the axial-F conformation in the parent protonated fluoropiperidinium compounds carries over to doubly alkylated salts, we show that it extends to molecular orientation in the packing of the unit cells in the solid state as well. Finally, using the computational methods that successfully motivated our synthesis and structural work, we have made predictions for a number of new structures and re-examined some parallel results reported by the Eliel group in the early 1970s. Although C-F...H-N hydrogen bonds are reported to be weak and few in number, the CF...HN charge-dipole orienting effect is a powerful directing force that matches the hydrogen-bond in both its energetic contribution and conformational consequences.

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Carbon‐13 NMR investigations of three fluorinated steroids

Carss

Harris

Fletton

1995

Magnetic Reson in Chemistry

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High-resolution carbon-13 NMR spectra were obtained for three solid fluorinated steroids. Assignments were carried out using several approaches, including twdimensional spectra of the compounds in solution. Solid-state and solution-state chemical shifts are compared. Signals from one of the fluorine-containing carbons in each compound show the e k t of interplay between shielding, dipolar and indirect scalar (J) coupling tensors. Ow sample is found to be a mixture of two polymorphic forms.

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¹H, ¹³C and ¹⁹F NMR spectral data for fifteen fluorinated steroids

Abstract: Analyses of the 1H, 13C and 19F NMR spectra of 15 mono‐, di‐, tri‐ or tetrafluoro‐substituted steroids were carried out by two‐dimensional 1H1H and 1H13C shift correlation experiments.

Cited by 6 publications

References 9 publications

Fluorine as an NMR probe for structural studies of chemical and biological systems

Fluorine as an NMR probe for structural studies of chemical and biological systems

3‐Fluoropiperidines and N‐Methyl‐3‐fluoropiperidinium Salts: The Persistence of Axial Fluorine

Carbon‐13 NMR investigations of three fluorinated steroids

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