Carbon-13 Magnetic Resonance Spectra Research Articles

The effect of the bilayer phase transition on the carbonyl carbon-13 chemical shift anisotropy

Proton enhanced (PE), natural abundance carbon-13 magnetic resonance spectra have been obtained of the carbonyl groups in hydrated dispersions of 1,2-dimyristoyl- sn-glycero-3-phosphocholine. A four-fold change in the overall linewidth results on passing from the fluid to crystalline phase. The carbonyl resonance provides a sensitive measure of the changes in mobility experienced by the lipid molecule above and below the phase transition temperature. The spectral shapes derived from both the fluid ( T = 45°C) and crystalline ( T = 15°C) phases indicate that even in the crystalline phase sufficient molecular motion is present to average the chemical shielding tensor. It is suggested that this motion in the L β′ phase is a result of dislocations and packing faults diffusing in the plane of the bilayer. Because of the small size of the chemical shielding interaction (approx. 3 kHz for ω 0 = 22.63 MHz) lipid diffusion coefficients of order 10 −10 cm 2/sec observed in the L β′ phase [1] are effective in averaging the shielding tensor. A comparison is made with the perturbation suffered by the carbonyl groups in the L α phase in the presence of substantial amounts of cholesterol or the polypeptide gramicidin A.

Biosynthesis of the Antibiotic Grananticin: Assignment of the Carbon-13 Magnetic Resonance Spectrum

Biosynthesis of the Antibiotic Grananticin: Assignment of the Carbon-13 Magnetic Resonance Spectrum

Biosynthesis of the Antibiotic Chlorothricin: Assignment of the Carbon-13 Magnetic Resonance Spectrum

Biosynthesis of the Antibiotic Chlorothricin: Assignment of the Carbon-13 Magnetic Resonance Spectrum

Carbon-13 magnetic resonance spectra of diamagnetic cyano complexes

Carbon-13 magnetic resonance spectra of diamagnetic cyano complexes

Carbon-13 Magnetic Resonance Spectra of Benzothiophene and Dibenzothiophene

Abstract The 13C n. m. r. spectra of benzothiophene and dibenzothiophene, not mentioned so far in literature are presented. The presence of six signals in the 13C {1H } n, m.r. dibenzothiophene spectrum confirms the symmetry of its electronic structure and magnetic effects and indicates the molecule to be flat. In the case of dibenzothiophene the carbons which are common to both the thiophene and benzene rings show somewhat lower chemical shifts if compared with benzothiophene.

13C nuclear magnetic resonance spectra of some C-19-hydroxy, C-5,6 epoxy, C-24 ethyl, and C-19-norsteroids

The carbon magnetic resonance spectra of a series of C-19 hydroxy, C-5β,6β epoxy, C-5α,6α epoxy, and C-24 ethyl steroids have been assigned. Shift parameters for the C-19 hydroxyl function are listed. The data presented has led to a reassignment of the published spectra of several C5α,6 α epoxy steroids. In addition, 13Cmr spectral data for several bicyclic enones and a Δ5(10)-3-estrone are presented.

Carbon-13 and proton magnetic resonance spectra of hexacarbonyltungsten methylenetriphenylphosphorane adducts

The adducts of methylenetriphenylphosphine with hexacarbonyltungsten have been studied by1H and13C n.m.r. spectroscopy. The methyl, (CO)5WC(OMe)CHPPh3, and trifluoromethanesulphonate, (CO)5WC(OSO2CF3)CHPPh3, derivatives have been prepared and an attempt has been made to prepare the acetylenic complex, $$(CO)_5 \bar WC \equiv C\mathop P\limits^ + Ph_3 $$ from these adducts.

Metabolites of bird's nest fungi. Part 10. Carbon-13 nuclear magnetic resonance studies on the cyathins

The carbon-13 magnetic resonance spectra of cyathin A3 and several related compounds have been measured and the chemical shifts have been assigned. The chemical shift data have been used to determine the stereochemistry at C-1 in cyafrin A4 and to determine the position of the bromine in 1-bromoallocyathin A3 methyl acetal.

Oxidation of methyl glycopyranosides by Acetobactersuboxydans

A synthesis of methyl pentopyranosid-4-uloses bas been achieved by microbiological oxidation by Acetobacter suboxydans of some methyl pentopyranosides. The oxidation products were isolated as their O-methyloxime derivatives, and the assignment of the configuration of the oximes was made on the basis of the carbon-13 magnetic resonance spectra. An analysis of the oxidative specificity of A. suboxydans towards methyl glycopyranosides is presented.

Carbon-13 and proton magnetic resonance spectra of 2,2-dialkyl-5,5-dimethylcyclohexane-1,3-diones (2,2-dialkyldimedones)

Proton and natural abundance carbon-13 Fourier transform n.m.r. spectra of ten 2,2-dialkyldimedones have been examined at 100 and 20 MHz respectively. Chemical shifts have been assigned in each case. In contrast to the significant long-range anisotropic shielding observed in the 1H n.m.r. spectra of 2-benzyl compounds, there was a slight deshielding of the corresponding carbon nuclei in the 13C spectra. The preparation of several new dialkyldimedones is also described.

Studies on nucleosides and nucleotides. LXXXI. Carbon-13 magnetic resonance spectra of 8-substituted purine nucleotides. Effects of various phosphate groups on the chemical shifts and conformation of nucleotides.

Carbon-13 magnetic resonance spectra of 8-substituted purine nucleotides and the corresponding parent nucleotides were measured. The 8-substituted derivatives included the 2'-, 3'-, 2', 3'-cyclic, 5'-and 3', 5'-cyclic phosphates of 8-bromoadenosine and the 5'-phosphates of 8-bromoguanosine, 8-methylinosine and 2-methylthio-8-methylinosine. All the 8-substituted nucleotides showed a characteristic upfield shift (-0.9 to -3.7 ppm) of the 2'-carbon with respect to the corresponding parent nucleotides. These results show that they take a syn conformation in aqueous solution to some extent. It was concluded from consideration of the sugar puckerings in the published PMR data that the 5'-phosphate of 8-bromoadenosine takes a more rigid syn conformation than the 2'-, 3'-and 2', 3'-cyclic phosphates. It is also suggested that 8-bromoadenosine has flexible glycosidic conformation similar to those for the latter compounds in water while in DMSO it adopts a more rigid conformation. The 5'-phosphates of the other 8-substituted nucleosides were also assumed to adopt a rigid syn conformation. The influences of various types of phosphate groups on the carbon chemical shifts are also discussed. Relatively large upfield shifts were observed for the C (4') signal of the 8-substituted 5'-nucleotides which has been assumed to be a reflection of a high population of non-gg conformations about the C (4')-C (5') bond.

Gardneria alkaloids. XII. Carbon magnetic resonance spectra of gardneria alkaloids. A study on the configuration of the side chain double bonds of indole alkaloids.

^ C-NMR spectra of several Gardneria alkaloids and their derivatives were studied. The chemical shifts of C(15) and C(21) were found to be diagnostic for the configuration of the side chain double bonds between C(19) and C(20). As a result of the present study the E configuration of the ethylidene side chain of chitosenine (V) was confirmed.

The Constituents of Rubus rosifolius. The Structure of Rosifoliol, a Biogenetically Significant Sesquiterpenoid

Chemical investigation of the steam-volatile oil of the shrub Rubus rosifolius yielded pregeijerene (2), β-caryophyllene (3), humulene (4), dihydroagarofuran (5), an unidentified sesquiterpene ether, hedycaryol (6) and the novel epieudesmol rosifoliol for which structure (1) is proposed. The bio- genetic significance of these constituents and the carbon-13 magnetic resonance spectra of rosifoliol and related compounds are discussed.

Three nuclei n.m.r. spectroscopy of dimethoate compounds. A large solvent effect on the 31PSC1H vicinal coupling

AbstractProton, phosphorus and carbon magnetic resonance spectra of dimethoate, dimethoxon, des‐N‐methyldimethoate, ω‐hydroxydimethoate, trimethyldithiophosphate and O,O‐dimethyldithiophosphate in different solvents have been measured. Most of the n.m.r. parameters were characteristic of the structural environment of the corresponding nucleus and solvent‐independent. However, in the amide structures dimethoate, dimethoxon, des‐N‐methyldimethoate and ω‐hydroxydimethoate the 31PSC1H vicinal coupling showed an unusually large solvent effect of a 2.3 to 6.5 Hz decrease when CDCI3 was replaced by acetone‐d6 or DMSO‐d6.

1H and 13C n.m.r. spectra of dichloro(trans‐2‐chlorovinyl)arsine

AbstractProton and carbon magnetic resonance spectra of Lewisite or dichloro(trans‐2‐chlorovinyl)arsine have been measured and the results are compared with the n.m.r. spectral parameters of other trans‐1,2‐substituted ethylenes. The coupling constants can be rationalized by substituent electronegativity. The chemical shifts show an unusually large paramagnetic effect from the AsCl2 group.

Carbon-13 magnetic resonance spectra of 8-substituted purine nucleosides. Characteristic shifts for the syn conformation.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCarbon-13 magnetic resonance spectra of 8-substituted purine nucleosides. Characteristic shifts for the syn conformationSeiichi Uesugi and Morio IkeharaCite this: J. Am. Chem. Soc. 1977, 99, 10, 3250–3253Publication Date (Print):May 1, 1977Publication History Published online1 May 2002Published inissue 1 May 1977https://doi.org/10.1021/ja00452a008RIGHTS & PERMISSIONSArticle Views358Altmetric-Citations136LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (479 KB) Get e-Alerts Get e-Alerts

Oxidation of a branched-chain alditol by Acetobacter suboxydans: A stereospecific synthesis of l-dendroketose

A synthesis of l-dendroketose ( 5) has been achieved by microbiological oxidation by Acetobacter suboxydans of the branched-chain alditol 2- C-(hydroxymethyl)- d- erythro-pentitol ( 4). Treatment of the oxidation product with acetone, copper(II) sulfate, and sulfuric acid afforded the two di- O-isopropylidene- l-dendroketose derivatives 6 and 7. Assignment of configuration at the branching carbon atom (C-4) and at the anomeric center in 6 and 7 was made on the basis of the carbon-13 magnetic resonance spectra of these derivatives.

Stereochemistry of quinolizidines. II. Carbon-13 magnetic resonance spectra of N-methylquinolizidinium ions.

The carbon magnetic resonance spectra of trans-(I) and cis-N-methylquinolizidinium ion (II) were examined in relation to the stereochemistry of these compounds. Ring inversion of the cis-N-methylquinolizidinium ion was observed in variable temperature experiments and results afforded ΔGc≠=13.7 kcal/mole. The observed carbon chemical shift difference between I and II was compared with that estimated empirically, and shown to be a measure of the stereochemical difference between the trans-and cis-forms of the quinolizidine nucleus.

13C-NMR of double and triple bond carbon atoms of unsaturated fatty acid methyl esters

The carbon magnetic resonance spectra of many fatty acid methyl esters with cis and trans double bonds and triple bonds at various positions and in many different combinations have been investigated. The influence of the ester group on double and triple bonds in the fatty acid chain depends strongly on the positions of these bonds. For a given position the influence is constant, even if one or more other double or triple bonds are present. Together with the evaluated chemical shift parameters for the effects of double and triple bonds on each other, complete assignments are possible and spectra of various types of unsaturated esters can be predicted with high accuracy (±0.1 ppm).

N.M.R. Spectral Studies of Some Quinolone Derivatives. Part V.1Further Studies of the Carbon-13 Magnetic Resonance Spectra of 2- and 4-Quinolone Derivatives

Abstract The 13C n.m.r. spectra of a series of 4-quinolone derivatives are presented and discussed, the existence of a peri shielding effect in the 2-quinolone series has been verified. Long range 13C - 1H coupling constants are reported for some methylquinolones which have been correlated with 1H - 1H coupling constants.