Carbon-13 chemical shift assignments of chromones and isoflavones

1980 ◽  
Vol 58 (12) ◽  
pp. 1211-1219 ◽  
Author(s):  
Hem Chandra Jha ◽  
Fritz Zilliken ◽  
Eberhard Breitmaier
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Chemical Shift Assignments ◽  
Resonance Effects ◽  
Naturally Occurring ◽  
Methoxy Groups ◽  
General Relations

Carbon-13 chemical shifts of 8 chromones and 35 isoflavones variously substituted by hydroxy-, acetoxy-, and methoxy-groups are assigned. The applicability of chemical shift increments reflecting inductive and resonance effects is discussed. Some general relations between substitution patterns and carbon shielding useful for the identification of naturally occurring isoflavones are outlined. Typical C—H couplings of chromone and phenyl carbons are analyzed for a 4′,6,7-trisubstituted derivative.

13C Chemical Shifts of Quinolizidines. 2. 13C Spectra of Some Nuphar Alkaloids

1975 ◽  
Vol 53 (12) ◽  
pp. 1714-1725 ◽  
Author(s):  
Robert T. LaLonde ◽  
Thomas N. Donvito ◽  
Amy I-M. Tsai
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Methyl Groups ◽  
Hydroxyl Groups ◽  
Chemical Shift Assignments ◽  
Oxide Formation ◽  
Model Compounds ◽  
Methyl Group ◽  
13C Chemical Shifts

The 13C n.m.r. spectra of nine Nuphar alkaloids: deoxynupharidine, 7-epideoxynupharidine, nupharidine, 7-epinupharidine, nupharolutine, 7-epinupharolutine, thiobinupharidine, thionu-phlutine B, and neothiobinupharidine, have been determined. Also examined were the spectra of five model compounds, 2,2,4,4-tetramethylthiolane, 3(a)-methyl-3(e)-methylthiomethylquinolizidine, 3(e)-methyl-3(a)-methylthiomethylquinolizidine, 3(e)-methylthio-3(a)-methylquinolizidine, and 3-methylfuran. This latter group of spectra were used to assist the chemical shift assignments of the Nuphar alkaloids. The most significant findings of this study are: (i) axial methyl and thiomethylene groups are shielded more than their equatorial counterparts in all cases; (ii) axial and equatorial hydroxyl groups substituted at C-7 of deoxynupharidine and 7-epideoxynupharidine give α-, β-, and γ-effects in ring B similar to those in carbocyclic systems but also produce small upfield shifts in ring A especially at the carbons α to nitrogen; (iii) the effect of a 3-furyl group located at C-4 appears to have nearly the same effect on quinolizidine ring carbons as a methyl group in the same position, the effects being shielding and deshielding at the various ring carbons; (iv) N-oxide formation results in α-, β-, γ-, and δ-shielding and deshielding effects consistent with the incorporation of an axial oxygen into a trans-fused system or the formation of a cis-fused quinolizidine N-oxide; and (v) methylene or methyl groups attached to C-2 and C-4 of a thiolane, including that in the skeleton of the C30 thiaspirane alkaloids, experience deshielding δ-effects.

A carbon-13 nuclear magnetic resonance study of a series of 5-substituted benzimidazoles

1982 ◽  
Vol 60 (24) ◽  
pp. 2987-3092 ◽  
Author(s):  
Barry J. Blackburn ◽  
Douglas W. Ankrom ◽  
Harold M. Hutton
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Nuclear Magnetic Resonance Study ◽  
Excess Charge ◽  
Chemical Shift Assignments ◽  
Magnetic Resonance Study ◽  
Nmr Chemical Shift Assignments ◽  
Density Values

Carbon-13 nmr chemical shift assignments are reported for a series of 5-substituted benzimidazoles, 2-methylbenzimidazole, and 5,6-dimethylbenzimidazole. By employing the three-parameter equation of Smith and Proulx, the chemical shifts of all the ring carbons of the 5-substituted compounds are correlated with F and R of Swain and Lupton and Q of Schaefer; only the ipso carbon, C-5, has chemical shifts with a correlation coefficient less than 0.953. These correlations are compared with those obtained from the Swain–Lupton and Taft relationships; in general those from the latter two approaches are found to be less satisfactory. Correlations of the same chemical shifts with excess charge density values, calculated at the INDO level of approximation, are also presented.

13C chemical shifts in medium ring and macrocyclic ketolactones

1977 ◽  
Vol 55 (18) ◽  
pp. 3261-3267 ◽  
Author(s):  
Jaswant R. Mahajan ◽  
Hugo C. Araújo
Keyword(s):  
Chemical Shift ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Natural Abundance ◽  
Chemical Shift Assignments ◽  
Substituted Benzenes ◽  
13C Chemical Shifts ◽  
Naphthalene Series ◽  
Medium Ring

Natural abundance 13C Ft nmr spectra of four different series of title compounds have been examined. Unambiguous chemical shift assignments could be made for all the carbons of the 11-membered cis-3,3-dimethyl-5-keto-6-alkyl-8-decenolides. In the rest of the 9- to 16-membered ketolactones, unique as well as logical assignments have been made using the standard 13C chemical shift rules. In the case of two benzo- and naphthoketolactone series examined, the available shielding parameters for the substituted benzenes were employed with success to the naphthalene series for the assignment of aromatic carbons.

Models for the assignment of the chemical shifts for protons on the epoxide ring of 2,3-anhydroglycopyranosides

1968 ◽  
Vol 46 (9) ◽  
pp. 1481-1486 ◽  
Author(s):  
F. Sweet ◽  
R. K. Brown
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Epoxide Ring ◽  
Chemical Shift Assignments ◽  
Close Resemblance ◽  
Proton Signal

The signal assignments for the protons of the epoxide ring in several 3,4-epoxy-2-alkoxytetrahydropyrans have been made by spin decoupling. Because of the close resemblance of these tetrahydropyrans to 2,3-anhydroglycopyranosides, these results have been used to make chemical shift assignments for the H-2 and H-3 protons of the latter compounds. For the compounds examined, the H-2 proton signal occurs at higher field compared to the position of the H-3 proton signal.

13C nuclear magnetic resonance spectra of steroids: the assignments of chemical shifts for C-15 and C-16 in 17β-acetyl steroids

1976 ◽  
Vol 54 (23) ◽  
pp. 3766-3768 ◽  
Author(s):  
Dong Je Kim ◽  
Lawrence D. Colebrook ◽  
T. J. Adley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Chemical Shift Assignments ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Previously reported 13C chemical shift assignments for C-15 and C-16 of a number of 17β-acetyl steroids related to progesterone have been shown to be reversed. Based on the revised assignment the effect of bromo- and hydroxy-substitution at C-17 on C-12, C-14, C-15, and C-16 is assessed.

scholarly journals Backbone and nearly complete side-chain chemical shift assignments of the human death-associated protein 1 (DAP1)

2020 ◽  
Author(s):  
Christoph Wiedemann ◽  
Johanna Voigt ◽  
Jan Jirschitzka ◽  
Sabine Häfner ◽  
Oliver Ohlenschläger ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Intrinsically Disordered Protein ◽  
Potential Interaction ◽  
Chemical Shift Assignments ◽  
Cell Growth And Migration ◽  
Structural Investigations ◽  
Intrinsically Disordered ◽  
Spectral Dispersion ◽  
And Migration

AbstractDeath-associated protein 1 (DAP1) is a proline-rich cytoplasmatic protein highly conserved in most eukaryotes. It has been reported to be involved in controlling cell growth and migration, autophagy and apoptosis. The presence of human DAP1 is associated to a favourable prognosis in different types of cancer. Here we describe the almost complete $${{^{1}}\text {H}}$$ 1 H , $${{^{13}}\text {C}}$$ 13 C , and $${{^{15}}\text {N}}$$ 15 N chemical shift assignments of the human DAP1. The limited spectral dispersion, mainly in the $${{^{1}}\text {H}{^{\text{N}}}}$$ 1 H N region, and the lack of defined secondary structure elements, predicted based on chemical shifts, identifies human DAP1 as an intrinsically disordered protein (IDP). This work lays the foundation for further structural investigations, dynamic studies, mapping of potential interaction partners or drug screening and development.

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