1H and13C NMR spectra of polycyclic compounds

Using 2D¹H and¹³C correlation NMR spectroscopy, all signals in the¹H and¹³C NMR spectra of five stereoisomeric bicyclo[2.2.1]heptadiene trimers, decacyclo[9.9.1.0^2.10.0^3.8.0^4.6.0^5.9.0^12.20.0^13.18.0^14.16.0^15.19]heneicosanes, obtained by Pd-catalyzed codimerization of norbornadiene dimer with quadricyclane followed by homocyclotrimerization of the latter were assigned unambiguously. Independent stereochemical identification of the trimers was performed using data on the nuclear Overhauser effect.     

1H and 13C NMR spectra of benzyl compounds

Proton and carbon-13 spectra of benzyl compounds of the general formula (C₆H₅CH₂)_nX with a large variety of X substituents have been measured. While a linear relationship between the CH₂ chemical shift and the substituent electronegativity was found both for ¹H and ¹³C, large deviations from linearity were observed for transition metals such as titanium and zirconium. These later results are correlated with the X-ray studies of the latter compounds.     

13C NMR spectra of biologically active compounds.

The¹³C spectra of 25 new substituted cyclopropanes of the pyrethoid series have been investigated and a stereochemical assignment has been made of the stereoisomers formed. As the criterion for stereochemical assignment it is proposed to use the values of the chemical shifts for the -carbon atoms of the substituents in the cyclopropane ring.Institute of Chemistry, Bashkir Branch, USSR Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 266–272, March–April, 1989.     

13C NMR spectra of biologically active compounds. VIII. Stereochemistry of a triterpeneglycoside — Glycyrrhizic acid — And its derivatives

Details of the¹³C NMR spectra of glycyrrhizic acid and four of its derivatives are given, and on their basis the configurations of the anomeric centers of the carbohydrate chain have been redetermined and the β-configuration of the C-1′ carbon atom has been suggested. Institute of Chemistry, Bashkir Scientific Center, Urals Branch, USSR Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 500–505, July–August, 1989.     

Research on 1-AZA two-ring systems. 21. Basicities,stereochemistry, and 1H and 13C NMR spectra of pyrrolizidine and its homologs in aqueous and aqueous acetonitrile solutions. Prediction of the pKa value of trans-fused pyrrolizidine

The basicities of pyrrolizidine and its homologs in aqueous and aqueous acetonitrile solutions at 25 ° C were determined. It is shown that among 3-alkylpyrrolizidines, the isomers with cis configurations have higher pK_a values than the isomers with trans configurations. On the basis of a comparative study of the ¹H and ¹³C NMR spectra it was concluded that cis-3,8-H-cis-5,8-H-3,5-dimethylpyrrolizidine in aqueous solutions exists chiefly in the trans-fused form, whereas conformationally heterogeneous pyrrolizidines with primarily cis-fused rings experience a shift of the equilibrium to favor an increase in the cis-fused conformations when a nonpolar solvent is replaced by a polar solvent. The basicity of the trans-fused conformation of pyrrolizidine is predicted on the basis of the data obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 39–46, January, 1982.     

Carbon-13 NMR spectra of retinal1 and its related compounds

Carbon-13 NMR spectra of all-trans retinal₁ and vitamin A₁ were measured by the pulse Fourier transform method in CCl₄. All peaks in these spectra were assigned from considerations of chemical shifts, half proton-decoupled spectra, spin-lattice relaxation times and induced chemical shift by the addition of shift reagent. The carbon-13 NMR spectrum was also measured for all-trans retinal₁ which had been exposed to the sunlight for three hours, and the induced isomer was proposed to be 11-s-cis retinal₁.     

13C NMR spectra of azolopyridines and their quaternary salts

¹³ C NMR spectra of some azole series have been investigated: 2-pyridylbenzimidazoles, 2-pyridylimidazo [4,5-b]-pyridines, 2-pyridylimidazo[4,5-c]-pyridines, analogous oxazole compounds, as well as their mono- and bisquaternary salts. Some problems, related to the structure of these compounds in solution, have been discussed.V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow 117975. Torino University, Italy. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 866–872, April, 1992.     

13C NMR spectra of biologically active compounds

The diastereomeric effects on the¹³C NMR chemical shifts of thirteen epimeric pairs of 16-aryloxy-11-deoxyprostaglandins of the E₁ and F₁ series caused by the change in the configuration of the 15-hydroxy group, which are differential parameters for assigning epimers to the 15- and 15-stereochemical series, have been determined.For Communication (VIII), see [1].Institute of Chemistry, Bashkir Scientific Center, Urals Branch, Academy of Sciences of the USSR, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 123–128, January–February, 1991.     

13C NMR spectra of benzofuroxan and related compounds

The ¹³C n.m.r. spectrum of benzofuroxan at ?15°C is assigned on the basis of selective decoupling experiments and by comparison with the ¹³C chemical shifts of model compounds. The ¹³C spectra were also measured in trifluoroacetic acid as a solvent. From the temperature dependence of the ¹³C spectrum of benzofuroxan in CDCl₃, a barrier of 14·0 ± 0·2 kcal mol^?1 is obtained for the degenerate tautomerism in this compound.     

13C NMR spectra of polycyclic compounds: Stereochemistry of trimers of bicyclo[2.2.1]heptadiene

¹³C NMR spectra have been obtained for six isomers of bicyclo[2.2.1]heptadiene (norbornadiene) trimers, and a complete stereochemical assignment of these isomers has been made by means of a computer-assisted calculation of chemical shifts.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1973–1978, September, 1990.     

13C NMR spectra of 3-substituted phlorophenone compounds

The ¹³C NMR spectra of a series of 3-allyl-, 3-prenyl- and 3-benzyl-phlorophenone compounds are reported. Relative substituent effects are discussed.     

13C NMR spectra of pyridinium betaines and related compounds

¹³C NMR spectra of 1-methyl-, 1-phenyl- and 1, 6-dimethyl-pyridinium-3-oxide, 3-methylphthalazinium 1-oxide and anhydro-3-methanesulphonamido-1-methylpyridinium hydroxide, together with the corresponding amines and quaternary salts, were determined with and without proton noise-decoupling. The assignment of resonances was based on the analysis of the fine splitting pattern caused by long range couplings whenever appropriate. A procedure for the estimation of chemical shifts of the salts and betaines is proposed.     

13C NMR spectra of handelin and its derivatives

The¹³C spectra of the diguaiane lactone handelin (I), deacetylhandelin (II), handelin diacetate (III), and deacetyldehydrohandelin (IV), and also cumambrin A (V) — a known sesquiterpene lactone that is a component part of the molecule of the compound (I) and is isolated together with it from a single source — have been studied. The identification of the resonance lines was based on a comparison with one another of the¹³C NMR spectra of compounds (I–IV) and (V) obtained under conditions of complete and partial decoupling from protons, and an analysis of the chemical shifts of certain carbon atoms of the model lactone cumambrin A and their comparison with the analogous parameters of handelin and its derivatives. The -, -, and -contributions of the neighboring groups to the chemical shifts of the carbon atom considered, and, in individual cases, the contributions due to steric factors, were also taken into account. A complete assignment of the lines of the spectra has been made on the basis of the comparative consideration performed.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 329–334, May–June, 1979.     

13C NMR spectra of bromine derivatives of fatty acids

Summary The¹³C spectra of the methyl esters of the cis and trans isomers of 9,10-dibromostearic, of cis,cis-9,10,12,13-tetrabromostearic, and of 10,11-dibromoundecanoic acid have been obtained, and the assignment of all the signals has been performed. It has been shown that the presence of bromine atoms in the chain of a fatty acid leads to the magnetic non-equivalence of the¹³C nuclei of the methylene groups present at a distance of three carbon-carbon bonds from the nucleus to which the halogen is directly attached. A dependence has been found of the shift parameter of the carbon nuclei in a fatty acid chain on the relative arrangement of the bromine atoms.V. I. Lenin Tashkent State University. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 26–30, January–February, 1977.     

13C n.m.r. spectra of some pyrylium salts and related compounds

The ¹³C chemical shifts of several alkyl and phenyl substituted pyrylium perchlorates, together with related pyridine and pyridinium salts, are reported. The shifts in the isoelectronic series benzene, pyridine, pyrylium cation correlate well with charge densities calculated by INDO MO theory. Charge densities also account for the shift changes found at C-3, C-4 and C-5 for protonation of pyridine and 2,4,6-trimethylpyridine. The shift changes observed on protonation for C-2 and C-6, along the series pyridine, 2,4,6-trimethylpyridine and 2,4,6-triphenylpyridine can only be rationalized by consideration of both charge density and π-bond order changes. The effects of alkyl substitution on the shifts of the pyrylium cations are not accounted for by charge density changes. Empirical correlations of these shifts with literature data for the alkylbenzenes and the shifts of the phenyl substituted 6-membered heterocycles are discussed.     

Configuration and 13C NMR spectra of 1-pyrazolines

A comparative study of the ¹³C spectra of 13 1-pyrazolines is reported. The results show that the chemical shifts of some carbons are very sensitive to the relative positions of substituents on the 3,4 and 4,5 bonds.     

1H and 13C NMR spectra of N-vinylpyrroles

The position of the substituants in 2, 3-dialkyl-1-vinylpyrroles and 7-methyl-1 vinyl-4,5,6,7-tetrahydroindole was established on the basis of the ¹H and ¹³C NMR spectra. It was found that the S-trans conformation of the N-vinyl group is preferred. It is shown that the condensation of ketoximes with acetylene proceeds through the formation of free pyrroles and that vinyl oximes are not intermediates in the condensation.     

13C NMR spectra of cephalosporins. Signal assignments of free acids and esters

¹³C NMR signals were assigned for several cephalosporin free acids and esters as well as cephalosporinate ions using T₁ measurements, selective NOE, and pD-dependent chemical shifts to investigate the structure-reactivity relationship.