Application Of 13C NMR Research Articles

Spectroscopic characterization of the 1-substituted 3,3-diphenyl-4-(2′-hydroxyphenyl)azetidin-2-ones: Application of 13C NMR, 1H– 13C COSY NMR and mass spectroscopy

The article deals with spectroscopic characterization of azetidin-2-ones. The presence of substituents like hydroxyl, fluoro, methoxy and benzhydryl, etc., on the azetidin-2-one ring significantly affects the IR absorption and 13C NMR frequencies of the carbonyl group present in these compounds. The presence of an ester carbonyl group or too many methine protons in the molecule has been observed to limit the scope of IR and 1H NMR spectroscopy in unambiguous assignment of the structure. The application of 13C NMR, 2D NMR ( 1H– 13C COSY) and mass spectroscopy in characterization of complex azetidin-2-ones is discussed. An application of the latter two techniques is described in deciding unequivocally between an azetidin-2-one ring and chroman-2-one ring structure for the product obtained by treatment of the 1-substituted 3,3-diphenyl-4-[2′-( O-diphenylacyl)hydroxyphenyl]-2-azetidinones with ethanolic sodium hydroxide at room temperature.

Application of13C NMR to the identification of surfactants in mixture

AbstractThe possibility of using the13C NMR technique as a preliminary screening for the analysis of manufactured household products is presented. Spectra for several surfactants and related products in water solution were obtained for reference. The application of13C NMR to commercial products shows that many surfactants can easily be distinguished from one another and determined from a single spectrum without laborious separative pretreatments.

Application of13C NMR in studying the dynamics and structure of liquid phenol

1. Correlation times τ of rotational motion of liquid phenol have been measured over a broad temperature range, as well as the correlation times of certain organic compounds dissolved in phenol. 2. The non-Arrhenius temperature dependences of τ, together with the temperaturerelated changes in anisotropy of rotation of the “guest” molecules, indicate strong association of phenol molecules. 3. By means of a modification of the theory of Steele and Huntress, the temperature dependence of τ has been calculated for phenol monomers, and it has been shown that void spaces may be formed in the phenol structure, with most probable dimensions 5–10 A.

Application of13C NMR spectroscopy and of fab mass spectrometry in the investigation of the minor triterpenoids ofThalictrum minus

Five minor triterpenoids have been isolated from the chloroform-soluble fraction of a methanolic extract ofThalictrum minus by chromatography on silica gel: (I) — oleanolic acid; (II) — oleanolic acid 3-0-α-L-arabinopyranoside; (III) — oleanolic acid 3-0-[0-β-D-glucopyranosyl-(1 → 3)-α-L-arabinopyranoside]; (IV) — oleanolic acid 3-0-[0-α-L-rhamnopyranosyl(1 → 2)-0-β-D-glucopyranosyl-(1 → 3)-α-L-arabinopyranoside]; and (V) — oleanolic acid 28-0-β-D-glucopyranoside 3-0-[0-β-D-glucopyranosyl-(1 → 3)-α-L-arabinopyranoside]. This is the first time that any of the compounds isolated have been detected in plants of the genusThalictrum. The possibility has been shown of determining the structures of triterpene glycosides on the basis of13C NMR spectroscopy and FAB mass spectrometry without chemical transformations of the glycosides.

Biotransformation and excretion: in vivo studies utilizing stable isotopes and nuclear magnetic resonance.

Specific 13C labeling in combination with nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for the study of metabolism. Nuclear magnetic resonance allows both the extent and distribution of 13C labels in metabolites to be quantified without the need to isolate or degrade them. In addition, NMR is nonperturbing to living cells, allowing real-time observation of metabolic processes. To date, the application of 13C-NMR to in vivo studies has been confined to the study of metabolic processes in cell suspensions, perfused organs, and small animals. The continuing development of large-bore high field magnets and surface coils will, in principle, allow in vivo metabolic studies to be extended to humans.

Some applications of13CNMR spectroscopy in heterocyclic structure assignments

The usefulness of13CNMR spectral data in solving otherwise intractable structural problems in heterocyclic chemistry is illustrated with ring systems such as imidazoles, pyrazoles, thiazoles, pyrimidines, benzodioxoles, benzodioxanes, benzoxazines, benzothiazines, quinoxalines, imidazopyrazoles, imidazothiazoles, pyridobenzoxazines, thiazolobenzimidazoles, thiazinobenzimidazoles, pyrimidobenzimidazoles, naphthodioxanes and perimidines. For example, using both chemical shifts and coupling constants, especially the one across three bonds, it has been possible to assign unique structures to the addition products of acetylenedicarboxylic esters to a variety of dinucleophiles such as thioureas, guanidines, 2-aminophenol, 2-aminothiophenol, 1,8-dihydroxy and 1,8-diaminonaphthalenes and 8-hydroxy-1,2,3,4-tetrahydroquinoline. These parameters also allow easy differentiation of isomeric imidazoles arising from N-alkylation of nitroimidazoles or nitration of imidazoles and of isomeric pyrazoles obtained from the reaction of hydrazines with ethoxymethylene derivatives of 1,3-dicarbonyl compounds.

Use of double-tuned surface coils for the application of 13C NMR to brain metabolism

Use of double-tuned surface coils for the application of 13C NMR to brain metabolism

Direct non-invasive observation of metabolism in living cells by 13C nuclear magnetic resonance spectroscopy

Applications of 13C nmr in following the metabolism and fate of 13C enriched substrates in whole cells are described. Studies on the elaboration of coproporphyrinogens I (2a) and III (2b) from [5-13C]-δ-aminolevulinic acid (1) and [11-13C-porphobilinogen (PBG, 3), in Rhodopseudomonasspheroides and Propionibacteriumshermanii, respectively, the randomization of 13C from [3-13C]-propionate by P. shermanii, the biosynthesis of citrate, gentisalcohol (4), and patulin (5) from [2-13C]-acetate by Penicilliumurticae, and the anaerobic metabolism of [1-13C]-glucose in rabbit erythrocytes are reported.