21,22-Disubstituted 18α,19βH-Ursane Derivatives with Oxabicyclooctane System in Ring E

1993 ◽  
Vol 58 (1) ◽  
pp. 173-190 ◽  
Author(s):  
Eva Klinotová ◽  
Jiří Klinot ◽  
Václav Křeček ◽  
Miloš Buděšínský ◽  
Bohumil Máca
Keyword(s):  
Spectral Data ◽  
Spin Systems ◽  
Coupling Constants ◽  
Complete Analysis ◽  
Nmr Spectrum ◽  
Proton Proton ◽  
H Nmr ◽  
Proton Coupling ◽  
C Nmr

Reaction of 3β-acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) and 20β,28-epoxy-21,22-dioxo-19α,19βH-ursan-3β-yl acetate (IIIb) with diazomethane afforded derivatives XII-XIV with spiroepoxide group in position 21 or 22, which were further converted into hydroxy derivatives XV and XVII. Ethylene ketals VIII-X were also prepared. In connection with the determination of position and configuration of the functional groups at C(21) and C(22), the 1H and 13C NMR spectral data of the prepared compounds are discussed. Complete analysis of two four-spin systems in the 1H NMR spectrum of bisethylenedioxy derivative Xb led to the proton-proton coupling constants from which the structure with two 1,4-dioxane rings condensed with ring E, and their conformation, was derived.

Concerning the conformational distribution in isopropylcyclopropane

1982 ◽  
Vol 60 (7) ◽  
pp. 845-847 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Roderick E. Wasylishen
Keyword(s):  
Methine Proton ◽  
Coupling Constant ◽  
Nmr Spectrum ◽  
Proton Proton ◽  
H Nmr ◽  
Proton Coupling ◽  
Trans Conformer ◽  
Partial Analysis ◽  
Vicinal Proton ◽  
Conformational Distribution

A partial analysis of the 400 MHz 1H nmr spectrum of isopropylcyclopropane yields 8.6 ± 0.2 Hz for the vicinal proton–proton coupling constant between a cyclopropyl proton and the methine proton of the isopropyl group. The fractional population of the s-trans conformer is estimated as 0.65 ± 0.l0 at 300 K, in reasonable agreement with molecular mechanics and INDO MO computations of the energies of the gauche and trans forms.The conformational preference of this molecule is similar to that in n-butane and in vinylcyclopropane but contrasts with that in biisopropyl and bicyclopropyl.

Darstellung und Kristallstruktur von endo-2-Dimethylphospliono-exo-2-liydroxy-(—)-camphan zur Bestimmung von 3J(CCCP)-Vicinalkopplungen / Synthesis and Crystal Structure of endo-2-Dimethylphosphono-exo-2-hydroxy-(—)-camphane for the Determination of 3J(CCCP) Vicinal Coupling Constants

1979 ◽  
Vol 34 (11) ◽  
pp. 1547-1551 ◽  
Author(s):  
Gunadi Adiwidjaja ◽  
Bernd Meyer ◽  
Joachim Thiem
Keyword(s):  
Coupling Constants ◽  
Coupling Constant ◽  
Nmr Spectrum ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Vicinal Coupling Constants ◽  
Complete Assignment ◽  
Hydroxy Phosphonates ◽  
C Nmr

endo-2-Dimethylphosphono-exo-2-hydroxy-(-)-camphane (2) is prepared and the structure confirmed by X-ray data. The complete assignment of the 13C NMR spectrum of this conformationally rigid derivative leads to a Karplus-type function for the vicinal 3J(CCCP) coupling constant in α-hydroxy phosphonates.

Structural revision of glabramycins B and C, antibiotics from the fungus Neosartorya glabra by DFT calculations of NMR chemical shifts and coupling constants

RSC Advances ◽  
2015 ◽  
Vol 5 (46) ◽  
pp. 36858-36864 ◽  
Author(s):  
Yang Li
Keyword(s):  
Natural Products ◽  
Dft Calculations ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Proton Proton ◽  
Structural Revision ◽  
Proton Coupling ◽  
Vicinal Proton ◽  
C Nmr

The 13C NMR spectra and vicinal proton–proton coupling constants of two tricyclic macrolactone natural products were analyzed using computational methods, which resulted in their structural revisions.

N.M.R. STUDIES: PART VI. THE COMPLETE ANALYSIS OF THE PROTON SPECTRA OF TWO ISOMERIC METHYL FLUOROBROMOPROPANOATES WITH THE AID OF HETERONUCLEAR SPIN DECOUPLING

1964 ◽  
Vol 42 (7) ◽  
pp. 1530-1541 ◽  
Author(s):  
J. B. Stothers ◽  
J. D. Talman ◽  
R. R. Fraser
Keyword(s):  
Double Resonance ◽  
Spin Systems ◽  
Coupling Constants ◽  
Complete Analysis ◽  
Proton Proton ◽  
Resonance Technique ◽  
Vicinal Proton ◽  
Isomeric Methyl

The 60 Mc/s proton spectra of methyl 2-bromo-3-fluoropropanoate and the 3-bromo-2-fluoro isomer have been analyzed completely with the aid of heteronuclear spin decoupling to illustrate an extension of the double resonance technique to ABCX spin systems. These results provide confirmatory evidence of the magnitude and relative signs of geminal and vicinal proton–proton and proton–fluorine coupling constants.

Concerning the extension of the J method for internal barriers to six-bond couplings to 19F in the 4-fluorophenyl fragment

1978 ◽  
Vol 56 (18) ◽  
pp. 2442-2446 ◽  
Author(s):  
Ted Schaefer ◽  
Werner Danchura ◽  
Walter Niemczura ◽  
James Peeling
Keyword(s):  
Ground State ◽  
Proton Magnetic Resonance ◽  
Coupling Constants ◽  
Side Chain ◽  
Fluorine Nucleus ◽  
Proton Proton ◽  
Proton Coupling ◽  
Carbon Carbon Bond ◽  
Internal Barriers

The long-range coupling constants over six bonds from the side-chain protons to the fluorine nucleus on the ring are extracted from the proton magnetic resonance spectra of p-fluorobenzyl cyanide, chloride, and bromide; of p-fluorobenzal chloride; and of p-fluoroisopropylbenzene. On the assumption that these couplings are transmitted via a σ–π mechanism, a hindered rotor treatment yields the barriers to internal rotation about the carbon–carbon bond which attaches the substituent to the benzene ring. These barriers, when compared to those derived from the analogous proton–proton coupling constants, apparently are accurate enough for the determination of ground state conformations and for a rough assessment of the energetics of conformational interconversions.

On Ruhemann's Purple

1980 ◽  
Vol 58 (3) ◽  
pp. 201-205 ◽  
Author(s):  
Donald C. Wigfield ◽  
Gerald W. Buchanan ◽  
Stephen M. Croteau
Keyword(s):  
Spectral Data ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Uv Visible ◽  
Ruhemann’S Purple ◽  
C Nmr

The 1H nmr spectrum previously reported for Ruhemann's Purple is shown to be inconsistent with the accepted structure of this material. The discrepancy with the reported 1H nmr spectrum is shown to be due to the presence of a major impurity, identified as hydrindantin. Spectra (1H nmr, 3C nmr, ir, uv–visible) of Ruhemann's Purple, its protonated analogue DYDA, and other ninhydrin relatives are reported, and structural conclusions are based on these spectral data.

1H NMR spectra of some chloro-alkenes

1981 ◽  
Vol 46 (11) ◽  
pp. 2924-2934
Author(s):  
Seán Cawley ◽  
Jan Schraml ◽  
Petr Svoboda ◽  
Robert Ponec ◽  
Václav Chvalovský
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Dipole Moments ◽  
Coupling Constants ◽  
The Other ◽  
Dominant Factor ◽  
Proton Proton ◽  
Electric Field Effects ◽  
H Nmr ◽  
Proton Coupling

1H NMR spectra and electric dipole moments of a series of propene derivatives, (CH3)3-nCln.CCH=CH2 (n = 0-3), were measured and the spectra analyzed. Discrepancies in literature data on compounds with n = 0 and 3 are probably due to systematic spectrometer errors. Vinylic proton chemical shifts are found to vary linearly with n in the direction expected on the electronegativity ground (the variations with n occurs in the order HA > HB ≥ HC). Calculations show that even with the extreme reported values of C-C and C-Cl bond magnetic anisotropies, the shift variations with n cannot be accounted for by magnetic anisotropy effects of a freely rotating (CH3)3-nClnC group. Similar calculations rule out electric field effects as the dominant factor. On the other hand, the electron charge distribution, as obtained from CNDO/2 calculations, including d-orbitals and employing Del Bene-Jaffé parametrization, is linearly related to the vinylic proton shifts. This finding supports the earlier interpretation of NMR spectra of vinylsilanes in terms of back-bonding. The vinyl proton-proton coupling constants decrease with increasing n, the changes being larger in the constants which couple proton A (cis) to the other two.

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