The 13C NMR spectrum of abietic acid and its methyl ester

The assignment of lines in the ¹³C NMR spectrum of abietic acid and its methyl ester have been made using carbon T₁ values and lanthanide induced shift effects. Structure–NMR parameter values are briefly discussed.     

The 13C NMR spectrum of coumarandione

A re-examination of the ¹³C NMR spectra of coumarandione and isatin with the aid of proton-coupled ¹³C NMR spectra and selective proton decoupling experiments is reported.     

Investigation of the structure of aminodicarboxylic acids by 13C NMR method

The protonation of ethylenediaminedisuccinic acid was investigated over a wide range of pH by the ¹³C NMR method. The degrees of protonation of the donor groups and the fractions of the trans and gauche conformers in the partially and fully protonated forms of this complexone were determined. A comparison is made of the conformational states of aspartic, iminosuccinic, and ethylenediaminedisuccinic acids. It is shown that complication in the structure has an effect on the conditions of the trans-gauche transitions, which determine the form of the ligand most favorable for combination with the metal ion.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 4, pp. 499–504, July–August, 1989.     

Interpretation of the 13C NMR spectrum of physostigmine

The 25.1 MHz ¹³C nmr spectrum of physostigmine in deuteriochloroform has been reanalysed with the aid of high resolution proton coupled spectrum and selective proton irradiation experiments. In addition to unambiguous assignment the analysis yielded values for carbon-proton coupling constants.     

13C NMR spectrum of lagochilin and its derivatives

Summary The¹³C NMR spectra of lagochilin and its derivatives have been studied. A complete assignment has been made of the lines of the spectrum and the values of the chemical shifts of the carbon atoms have been discussed in connection with the spatial structure of the molecules of these compounds.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 41–43, January–February, 1979.     

13C NMR spectra and the structure of dithizone

The structural characteristics of dithizone in the solid state and in solution were studied by a high-resolution¹³C NMR method. A highly symmetrical structure of dithizone was established in the crystalline state, and it was suggested that it exhibits dual behavior in complexation reactions with metal ions.V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 117975 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 113–117, January, 1992.     

Synthesis, 13C NMR spectrum and crystal structure of 10-Phenylpyrido[3,2-b][1,4]benzothiazine 5-Oxide

The compound 10-phenylpyrido[3,2-b][1,4]benzothiazine 5-oxide, 1 , has been obtained in nearly quantitative yield oxidation of 10-phenylpyrido[3,2-b][1,4]benzothiazine with oxygen in dioxane solution. The ¹³C nmr chemical shift assignments of 1 are reported. Its structure has been determined by X-ray single crystal methods. The crystals of 1 are monoclinic, space group P2₁/n. There are four molecules in a unit-cell of dimensions a = 12.347(3), b = 12.947(3), c = 8.987(1)Å, β = 106.73(1)° and V = 1375.8(5) ų. The central ring is in a boat conformation and the sulfoxide oxygen atom occupies the axial position. The folding angle between the planes of the pyrido and the benzo planes is 161.55(9)°.     

13C NMR Investigation of Si-alkylsubstituted 1,3,5-Trisilacyclohexanes

¹³C NMR spectra of Si-alkylsubstituted derivatives of 1,3,5-trisilacyclohexanes have been recorded and analyzed. A systematic preparation of alkyl derivatives with mixed substituents made it possible to evaluate substituent-induced chemical shift (SCS) values for the ring carbon atoms in β and δ position. It is found that the β_e effect decreases in the order Me > Et > i-Pr > t-Bu. For the alkyl groups Me, Et, and i-Pr the β_a effect is smaller than the β_e effect. Axial SCS values for the t-Bu group are not accessible because chair conformations with an axial t-Bu group are unfavourable and tend to escape into a twisted boat form. The observed δ effects are small and do not show any obvious tendencies.     

The 13C NMR spectrum of 5- O-β-D-primeverosyl genkwanine

The ¹³C NMR spectra of 5-O-β-D-primeverosyl genkwanine and its acetate are studied and assignments are proposed.     

1H and 13C NMR studies of lanthanide complex with 5-sulfosalicylic acid

In this paper, paramagnetic shifts have been measured for all ¹H and ¹³C nuclei of 5-sulfosalicylic acid (SSA) in the presence of the lanthanide ions in the second half of the series. The ligand forms isostructural complexes with these ions in aqueous solution. The separation of LISs was carried out by the use of the Reilley method and the calculated dipolar shifts were used to simulate the coordination structure of the complex. The result reveals that SSA is coordinated to lanthanide ion via two oxygens, one from the carboxylic group and the other from the phenolic group with Ln–O bond lengths equal to 2.47 Å. The lanthanide ion lies on the benzene plane and the carboxylic group is twisted 20° from the benzene ring. Of all the nuclei examined, those in the six-membered chelate ring experience significant dipolar interactions and contact interactions. Small |G/A| ratios were obtained for two protons five bonds away from the central lanthanide ion, which shows that the number of bonds alone cannot be used as a criterion for neglecting contact shifts in aromatic ligand.     

13C NMR spectra and electronic structure of alkenylalanes

The parameters of¹³C NMR spectra of linear and cyclic alkenylalanes synthesized from mono- and disubstituted acetylene and the simplest alkylalanes have been obtained. A strong paramagnetic effect of the aluminum atom on shielding of α- and β-carbon atoms at the double bond has been observed for the dimeric form of organoaluminum compounds (OAC) in inert solvents, unlike that for the monomeric form solvated in electron-donor solvents (Et₂O, THF, and Et₃N). The results were interpreted in terms of the model of the electron density redistribution on going from the dimeric structure of OAC to the monomeric one. The PM3 method describes most adequately (as compared to MNDO and AM1) the equilibrium geometry of cyclic dimers of OAC.     

13C NMR spectra and structure of some coumarin derivatives

The results are given of a study of the¹³C NMR spectra of (?)-3(R)-decursinol, obtusifol, bergapten, isoimperatorin, and oxypeucedanin and its hydrate. The possibility has been shown of using the principle of additive contributions in the assignment of the signals of the carbon atoms in the compounds under investigation.     

13C NMR spectra of 5-substituted 8-mercaptoquinolines

The increments of the substituents were determined from the ¹³C NMR spectra of 5-substituted quinolines. It is shown that the increments correlate with those in benzenes, as well as with the Swain-Lupton constants. The ¹³C chemical shifts of some 5-substituted 8-mercapto-, 8-(methylthio)-, and 8-hydroxyquinolines were investigated. Their values are in satisfactory agreement with the additive contribution. of the increments of the substituents. The deviations from additivity are associated with the steric hindrance to interaction of the substituents with the ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 932–936, July, 1981.     

Comprehensive 1H and 13C NMR assignment of 13 protobassic acid saponins

This study aimed to carry out complete ¹H and ¹³C NMR assignment of 13 protobassic acid saponins, including arganins A–C ( 1 – 3 ) and F ( 4 ), butyrosides B–D ( 5 – 7 ), tieghemelin ( 8 ), 3′-O-glucosyl-arganin C ( 9 ), Mi-saponins A–C ( 10 – 12 ), and mimusopsin ( 13 ), recorded in methanol-d₄. This was accomplished by the analysis of high-resolution one-dimensional (1D) NMR (¹H and ¹³C), two-dimensional (2D) NMR (¹H–¹H COSY, HSQC, and HMBC), and selectively excited 1D TOCSY spectra. Before this study, ¹H and ¹³C NMR data of arganins A–C ( 1 – 3 ) and F ( 4 ) were partially assigned. Our effort leads to their complete assignment, especially the glycon residue, and revises some reported data. Some revisions of the ¹H and ¹³C NMR data in the glycon part of butyroside C ( 6 ), tieghemelin ( 8 ), Mi-saponin A ( 10 ), and mimusopsin ( 13 ) were made. Those data of butyrosides B and D ( 5 & 7 ) and Mi-saponin B ( 11 ), which had not been recorded in methanol-d₄, are provided. In addition, the ¹H and ¹³C NMR data of Mi-saponin C ( 12 ) are reported for the first time. These data, being recorded in methanol-d₄, should be more friendly for use as a reference for identifying the related triterpenoid saponins.