Carbon-13 nuclear magnetic resonance spectra of N-, O-, and S-methylated uracil and thiouracil derivatives

1978 ◽  
Vol 56 (5) ◽  
pp. 725-729 ◽  
Author(s):  
Ian W. J. Still ◽  
Nick Plavac ◽  
David M. McKinnon ◽  
Mohinder S. Chauhan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Chemical Shift ◽  
General Type ◽  
Chemical Shifts ◽  
Pyrimidine Derivatives ◽  
Aromatic Substituent ◽  
Nuclear Magnetic Resonance Spectra ◽  
Derivatives Of ◽  
Thiouracil Derivatives ◽  
C Nmr

13C nmr chemical shifts have been recorded for a number of uracil, thiouracil, and pyrimidine derivatives. These data are discussed in relation to what is known of the lactam–lactim tautomerism in such systems and possible correlations of chemical shifts with normal aromatic substituent chemical shift parameters. The chemical shifts for the CH3 groups in simple methylated derivatives of uracil are very characteristic of the site of methylation and should prove useful as a tool for assigning structures to alkylated derivatives of this general type.

Carbon-13 nuclear magnetic resonance spectra of organic sulfur compounds. Comparison of chemical shifts for carbonyl and thiocarbonyl compounds in the pyrone, thiopyrone, and pyridone series

1976 ◽  
Vol 54 (2) ◽  
pp. 280-289 ◽  
Author(s):  
I. W. J. Still ◽  
N. Plavac ◽  
D. M. McKinnon ◽  
M. S. Chauhan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Conjugated Systems ◽  
Organic Sulfur Compounds ◽  
Nmr Data ◽  
Nuclear Magnetic Resonance Spectra ◽  
Related Series ◽  
Sulfur Containing ◽  
C Nmr

13C nmr data have been obtained for a series of 2- and 4-pyrones and pyridones, and their sulfur-containing analogues. Correlations have been observed between the nature of the ring hetero-atom and the chemical shift difference (Δδ) for the Cα and Cβ carbons in these conjugated systems. No significant correlation, however, appears to exist between the chemical shifts of the C=O and C=S groups. Substituent chemical shift (s.c.s.) effects for various simple substituents are compared with those in related series of compounds.

scholarly journals Carbon-13 nuclear magnetic resonance spectra of oxazoles

1979 ◽  
Vol 57 (23) ◽  
pp. 3168-3170 ◽  
Author(s):  
Henk Hiemstra ◽  
Hendrik A. Houwing ◽  
Okko Possel ◽  
Albert M. van Leusen
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Proton Coupling ◽  
Nuclear Magnetic Resonance Spectra ◽  
C Nmr ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 13C nmr spectra of oxazole and eight mono- and disubstituted derivatives have been analyzed with regard to the chemical shifts and the various carbon–proton coupling constants of the ring carbons. The data of the parent oxazole are compared with thiazole and 1-methylimidazole.

Carbon-13 nuclear magnetic resonance studies of organotellurium compounds. II. Chemical shift trends

1982 ◽  
Vol 60 (5) ◽  
pp. 596-600 ◽  
Author(s):  
Raj. K. Chadha ◽  
Jack M. Miller
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Magnetic Resonance Studies ◽  
Nmr Chemical Shifts ◽  
Organic Group ◽  
Opposite Trend ◽  
Organotellurium Compounds ◽  
C Nmr

13C nmr chemical shifts are reported for some aromatic and aliphatic tellurium compounds. For a given organic group, the shift of the C1 atom varies in the order [Formula: see text], as expected from electronegative considerations. The C2 atom experiences an opposite trend while the C3 and C4 atoms of the ring experience smaller changes. The chemical shifts of para-substituted aromatic tellurium compounds do not show additivity of contributions from the substituents.

Synthesis and nuclear magnetic resonance spectra of some partially acylated β-D-glucopyranosides

1968 ◽  
Vol 46 (15) ◽  
pp. 2485-2493 ◽  
Author(s):  
A. P. Tulloch ◽  
A. Hill
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Trimethylsilyl Ether ◽  
Ether Group ◽  
Nuclear Magnetic Resonance Spectra ◽  
The Difference ◽  
Derivatives Of ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The synthesis of ten new partially acylated derivatives of methyl β-D-glucopyranoside, all with an acyl group at C-6, is described. The nuclear magnetic resonance spectra of these compounds, and of a number of related derivatives, have been measured using pyridine, acetone-d6, and deuteriochloroform as solvents. When OH-4 is acylated, the H-6 signals are at higher field (by 0.1–0.3 p.p.m.) than when OH-4 is not acylated, but this effect is not observed when OH-3 is acylated. When a trimethylsilyl ether group is introduced at C-4 the difference between the chemical shifts of the H-6 protons (δA –δB) increases markedly. Estimation of JBX and JAX (where B is the H-6 proton at higher field and X is H-5), from spectra obtained using acetone-d6 and pyridine as solvents, shows that JBX < JAX when there is an acyl group at C-4 but JBX > JAX when there is no acyl group at C-4.

Selenium-77 nuclear magnetic resonance studies of selenols, diselenides, and selenenyl sulfides

1988 ◽  
Vol 66 (1) ◽  
pp. 54-60 ◽  
Author(s):  
Khoon-Sin Tan ◽  
Alan P. Arnold ◽  
Dallas L. Rabenstein
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Proton Exchange ◽  
Exchange Reactions ◽  
Nuclear Magnetic Resonance Spectra ◽  
Ph Range ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

77Se and 1H nuclear magnetic resonance spectra have been measured for selenols (RSeH), diselenides (RSeSeR), and selenenyl sulfides (RSeSR′), including selenenyl sulfides formed by reaction of glutathione and penicillamine with selenocystine and related diselenides. Exchange processes strongly affect the 77Se and 1H nuclear magnetic resonance spectra of all three classes of compounds. Sharp, exchange-averaged resonances are observed in the 1H nuclear magnetic resonance spectra of selenols; however, selenol proton exchange causes the 77Se resonances to be extremely broad over the pH range where the selenol group is titrated. Selenol/diselenide exchange [Formula: see text] also results in exchange-averaged 1H resonances for solutions containing RSeH and RSeSeR; however, the 77Se resonances were too broad to detect. Exchange reactions have similar effects on nuclear magnetic resonance spectra of solutions containing selenols and selenenyl sulfides. The results indicate selenol/diselenide exchange is much faster than thiol/disulfide exchange. The 77Se chemical shift depends on the chemical state of the selenium, e.g., titration of the selenol group of selenocysteamine causes the 77Se resonance to be shielded by 164 ppm, oxidation of the selenol to form the diselenide selenocystamine causes a deshielding of 333 ppm, and oxidation to form the selenenyl sulfide [Formula: see text] results in a deshielding of 404 ppm. 77Se chemical shifts were found to be in the range −240 to −270 ppm (relative to (CH3)2Se) for selenolates, approximately −80 ppm for selenols, 230–360 ppm for diselenides, and 250–340 ppm for selenenyl sulfides. The 77Se chemical shift is also affected by titration of neighboring carboxylic acid and ammonium groups, and their pkA values can be calculated from 77Se chemical shift data.

CYCLOHEXANE COMPOUNDS: IV. NUCLEAR MAGNETIC RESONANCE SPECTRA OF SOME DERIVATIVES OF THE STEREOISOMERIC 3-AMINO-1,2-CYCLOHEXANEDIOLS

1963 ◽  
Vol 41 (9) ◽  
pp. 2331-2338 ◽  
Author(s):  
F. A. L. Anet ◽  
R. A. B. Bannard ◽  
L. D. Hall
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Room Temperature ◽  
Conformational Equilibrium ◽  
Chemical Shifts ◽  
Chloroform Solution ◽  
Coupling Constants ◽  
Order Analysis ◽  
First Order ◽  
Nuclear Magnetic Resonance Spectra ◽  
Derivatives Of

The n.m.r. spectra of 1α-methoxy-2β-hydroxy-3α-aminocyclohexane, 1α-methoxy-2α-hydroxy-3β-aminocyclohexane, their N-acetyl and O,N-diacetyl derivatives, ethoxy analogues, and 3α-amino-1α,2β-cyclohexanediol and 3β-amino-1α,2β-cyclohexanediol triacetates were measured in chloroform solution. From the chemical shifts of the O- and/or N-acetyl methyl protons it was possible to assign conformations to all the substituted derivatives and in most cases the assignments thus made were confirmed by first-order analysis of the multiplet pattern from the methine protons. In all cases, the conformations found were those predicted on simple conformational grounds and no evidence for a conformational equilibrium at room temperature was obtained from the coupling constants. In general, the coupling constants for the methine protons followed the pattern predicted by the Karplus equation. Acetylation of the 1α-alkoxy-2α-hydroxy-3β-aminocyclohexanes with acetic anhydride gave both the O,N-diacetyl derivative and the O,N,N-triacetyl derivative.

Nuclear magnetic resonance spectra of pyrrolizidine alkaloids. II. The pyrrolizidine nucleus in ester and non-ester alkaloids and their derivatives

1965 ◽  
Vol 18 (10) ◽  
pp. 1625 ◽  
Author(s):  
CCJ Culvenor ◽  
WG Woods
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Pyrrolizidine Alkaloids ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Vicinal Coupling Constants ◽  
Nuclear Magnetic Resonance Spectra ◽  
Saturated Ring ◽  
Magnetic Resonance Spectra

Chemical shifts and coupling constants are tabulated for the protons of the pyrrolizidine nucleus in 40 pyrrolizidine alkaloids and derivatives. The effect of acylation of hydroxyl substituents on C7 and C9 and the very large difference in chemical shift of the H9 protons in the macrocyclic diester alkaloids is discussed. The direction of buckling of the saturated ring can be ascertained from the H5,H6 vicinal coupling constants or from the width of the H7 multiplet if H7 bears an oxygen substituent. In general, retronecine derivatives are exo-buckled whereas heliotridine derivatives consist of interconverting exo- and endo-buckled forms.

13C nuclear magnetic resonance spectra of alkyl indoles including derivatives of hexahydroechinulin

1976 ◽  
Vol 54 (18) ◽  
pp. 2915-2918 ◽  
Author(s):  
Robert R. Fraser ◽  
Salvatore Passannanti ◽  
Franco Piozzi
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Original Data ◽  
Single Frequency ◽  
Methyl Groups ◽  
Methyl Substituent ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
A Site ◽  
Derivatives Of ◽  
C Nmr

Revised structures for 4-bromohexahydroechinulin and 6-nitrohexahydroechinulin have been established using 13C nmr spectroscopy. For this purpose the substituent parameter for the nitro group at a site flanked by two methyl groups has been measured. Inconsistencies in previous data on alkyl indoles in comparison with hexahydroechinulin suggested a reassignment of the C4 and C6 signals in 5-methylindole, which we have proven by single frequency spin-decoupling experiments. The original data on methyl indoles has been retabulated to include the above reassignments and others recently reported by Gribble et al. A more consistent and reliable set of methyl substituent parameters is thereby obtained.

Carbon-13 nuclear magnetic resonance spectra of organic sulfur compounds. Substituent chemical shift (s.c.s.) effects in the 4-thiazoline-2-thione series

1976 ◽  
Vol 54 (10) ◽  
pp. 1660-1664 ◽  
Author(s):  
I. W. J. Still ◽  
N. Plavac ◽  
D. M. McKinnon ◽  
M. S. Chauhan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Sulfur Compounds ◽  
Organic Sulfur ◽  
Organic Sulfur Compounds ◽  
Nmr Data ◽  
Nuclear Magnetic Resonance Spectra ◽  
C Nmr ◽  
Magnetic Resonance Spectra

13C nmr data have been obtained for a series of 4-thiazoline-2-thiones. Substituent chemical shift (s.c.s.) effects for methyl and phenyl substitution have been collated and are discussed in comparison with s.c.s. effects in other heterocyclic systems. Some attempt has also been made to compare our data with those reported previously for the thiazoles and for some thiones in the isothiazole series.

Sign in / Sign up

Export Citation Format

Share Document