N.M.R. studies of aldonolactones. The 80-MHz proton N.M.R. and 20-MHz proton-coupled 13C N.M.R. of D-Arabinono-1,4-lactone in D2O solutions

1984 ◽  
Vol 37 (2) ◽  
pp. 327 ◽  
Author(s):  
H Wong
Keyword(s):  
Computer Simulations ◽  
Coupling Constants ◽  
Dihedral Angles ◽  
Proton Coupling

The 80-MHz proton n.m.r. spectrum of D-arabinono-1,4-lactone in D2O has been simulated and the results utilized in the assignment of the 20-MHz proton-coupled 13C n.m.r. spectrum. Two-and three-bond carbon-proton coupling constants have been derived from computer simulations and are discussed in terms of the dihedral angles in the preferred conformation.

The Proton–Proton and Proton–Carbon-13 Spin–Spin Coupling Constants in 1,3-Dioxole and Bis-1,3-dioxolyl. Conformational Dependence

1975 ◽  
Vol 53 (18) ◽  
pp. 2734-2741 ◽  
Author(s):  
Ted Schaefer ◽  
Kalvin Chum ◽  
David McKinnon ◽  
M. S. Chauhan
Keyword(s):  
Double Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Dihedral Angles ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton ◽  
Karplus Relationship ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The carbon-13 satellite peaks in the proton magnetic resonance spectra of 1,3-dioxole and bis-1,3-dioxolyl are analyzed under single and double resonance conditions to yield the signs and magnitudes of proton–proton coupling constants over three, four, and five bonds, and of proton–carbon-13 coupling constants over one, two, and three bonds. The conformational behavior of bis-1,3-dioxolyl contrasts sharply with that of analogous sym-tetrasubstituted ethane derivatives. It is indicated that the two-bond proton–carbon-13 coupling in the ethanic fragment can be used for conformational analysis in a manner similar to vicinal proton–proton couplings. The vicinal three-bond proton–carbon-13 couplings are given for dihedral angles of 180 and 120° and their relative magnitudes are as expected from a Karplus relationship. The two-bond proton–carbon-13 coupling in the olefinic fragment is, at 20.0 Hz, the largest coupling known for such a bond.

Conformations of Sugars: Proton Dihedral Angles from Gauche Coupling Constants

1974 ◽  
Vol 52 (24) ◽  
pp. 4095-4100 ◽  
Author(s):  
T. P. Forrest
Keyword(s):  
Dihedral Angle ◽  
Coupling Constants ◽  
Dihedral Angles ◽  
General Applicability ◽  
Karplus Equation ◽  
Proton Coupling ◽  
Equatorial Proton ◽  
Derivatives Of ◽  
Equatorial Substituent

Proton coupling constants have been used in calculating dihedral angles of vicinal gauche protons in variety of pyranose derivatives of glucose, mannose, arabinose, xylose, altrose, and galactose. The calculations involve the use of a formula which was derived from a correlation of the coupling constants of ethane derivatives with the electronegativities of substituents and their orientation relative to the coupled protons.The results indicate that the formula has general applicability and gives more reasonable values than a Karplus equation in which the constants have been adjusted to fit some compounds of the series. The calculated dihedral angles indicate that an equatorial substituent generally causes little distortion of dihedral angles, whereas an axial substituent generally causes the equatorial proton on the same carbon to have a smaller than normal dihedral angle with the adjacent axial proton and a larger than normal dihedral angle with the adjacent equatorial proton.

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.

Proton magnetic resonance study of the conformation of the pyrrolidine ring in some proline-thiohydantoins

1988 ◽  
Vol 53 (11) ◽  
pp. 2503-2510 ◽  
Author(s):  
Jef J. M. Sleeckx ◽  
Marc J. O. Anteunis ◽  
Frans A. M. Borremans
Keyword(s):  
Present Model ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Proton Magnetic Resonance Study ◽  
Vicinal Proton ◽  
Different Temperatures ◽  
Experimental Justification ◽  
State Assumption ◽  
Methyl Phenyl

The conformational behaviour of a series of N-substituted thiohydantoins of proline was studied by proton NMR. The pseudorotational parameters of the proline moiety were calculated from the ten vicinal proton-proton coupling constants assuming a two state equilibrium (N ⇋ S). The effect of the different substituents (methyl, phenyl, para-nitrophenyl) at the thiohydantoin nitrogen on the conformation of the pyrrolidine rings is discussed. The spectra of proline-N-methylthiohydantoin were recorded at different temperatures in octadeuterotoluene solution. The conformational analysis of these spectra showed that the ratio of the populations of the N and S forms changes considerably with temperature, while the conformational identity of both the N and S forms remains strictly preserved. These facts provide an additional experimental justification of the two-state assumption, at least so for the present model compounds.

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