13C NMR spectra of 1-stearoyl-2-linoleyl-sn-glycero-3-phosphorylcholine and 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine in CDCl3 solution and in sonicated dispersions in 2H2O

Two mixed-acid lecithins: 1-stearoyl-2-linoleyl-sn-glycero-3-phosphorylcholine (SLL) and 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (SAL) have been synthesized by phospholipase A₂ digestion of 1,2-distearoyl-sn-glycero-3-phosphorylcholine (DSL), followed by reacylation of the lysolecithin with the desired fatty acid anhydride. ¹³C (25.2 MHz) NMR spectra of SLL and SAL in CDCl₃ solution and in sonicated dispersions in ²H₂O have been obtained. Complete spectral assignments are reported for the two molecules in both systems. ¹³C nuclear spin-lattice relaxation times (T₁) of SLL and SAL in sonicated aqueous dispersions have also been measured. Relaxation rate profiles as a function of the chain segment position are in general agreement with those recently obtained from ²H NMR for similar systems.     

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.     

1H and 13C NMR spectra of N-substituted morpholines

(1)H and (13)C NMR data for N-substituted morpholines 1-20 were measured using 1D (DEPT, 1D NOE difference) and 2D NMR spectroscopic methods including (1)H-(1)H COSY, long-range (1)H-(1)H COSY, NOESY, gHMBC and gHMQC experiments. At room temperature the (1)H NMR spectra of protonated compounds 2 and 9 show the chair conformation for the morpholine ring. Spin-spin coupling constants were deduced from the resolution-enhanced proton spectra.     

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.     

Hydrogen bonding of N-methylacetamide in CDCl3 solution studied by NMR and IR spectra

The amide proton NMR chemical shifts have been widely used for the determination of the population fraction of the non-hydrogen-bonded states in studies of hydrogen bonding in peptides and proteins. However, in such works the determination of the limiting chemical shifts for the fully hydrogen-bonded state and for the non-hydrogen-bonded state is quite problematic, because they cannot be measured directly. In the present study, we carried out variable-temperature ¹H NMR and IR measurements for N-methylacetamide in CDCl₃ solution. We derived the expression for the limiting chemical shift for the fully hydrogen-bonded state as a function of IR band intensity and chemical shift. According to the equation, we determined the values of the limiting shifts at various temperatures. The present method may be applicable to other hydrogen-bonding systems.     

13C and proton NMR spectra of 2(1H)pyrazinones

¹³C and proton NMR spectra data are given for eleven 2(1H)pyraziones. Assignments of chemical shifts were made by methods which included: deuterium exchange with certain protons of 3-alkyl substituents; change of chemical shifts of certain carbon atoms with change in pH; the use of long-range coupling constants for ¹³C to protons; and various correlations among assigned spectra.     

1H and13C NMR spectra of 3-methyl-3-cyanocyclopropene and 3-phenyl-3-methylcyclopropene

Conclusions The¹H and¹³C NMR spectral parameters were found for 3-methyl-3-cyanocyclopropene and 3-phenyl-3-phenyl-3-methylcyclopropene. The proton-carbon coupling constants indicate the acetylenic nature of bonding in the cyclopropene ring.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1405–1408, June, 1985.     

1H and 13C NMR spectra of new 2-thiabicyclo[3.2.0]hept-3-enes

Three new compounds, one with the molecular formula C₆H₈S and two corresponding to C₇H₁₀S have been isolated together with the main product, divinyl sulphide, from the reaction products of acetylene with sodium sulphide. Structure determination through ¹H and ¹³C NMR with selective ¹³C? {¹H} decoupling, showed C₆H₈S to be a new heterocyclic compound, 2-thiabicyclo[3.2.0]hept-3-ene, and the two C₇H₁₀S compounds its exo- and endo-6-methyl derivatives. Since the spectral parameters of these heterocycles were not known, all possible structures corresponding to the molecular formulae were considered.     

2H and 13C NMR spectra of deuterated adamantan-2-ols

The composition of a mixture of adamantan-2-ol and its two epimeric 4-deuterio derivatives was determined by ²H NMR spectroscopy with the aid of Eu(fod)₃. In addition, unambiguous assignments of the two H-4 signals and the two δ carbon signals were possible; these assignments had previously been speculative.     

1H and 13C NMR spectra and solution structures of novel derivatives of 5-substituted creatinines

Five creatinine derivatives were prepared by the treatment of creatinine with activated carbon and appropriate alcohol (1-4), or ammonia solution (5). Product structures were determined by 1H and 13C NMR spectroscopy in solution, including 2D HSQC and HMBC experiments. Then, the proton and carbon chemical shifts for these compounds were calculated using GIAO-DFT [B3LYP/6-311G(2d,p)] method and the Gaussian 03W program and furthermore for 1 and 5 using polarizable continuum model (PCM). The conclusions coming from the comparison of the experimental and theoretical spectra supported the adopted signal assignments and solved the structural problems due to the potential annular tautomerism of the investigated compounds. One can predict that 5-substituted creatinines, just like creatinine, appear in solution in the form of 2-amino-1,5-dihydro-1-methyl-4-imidazolone. Correlations between experimental and calculated substituent-induced chemical shifts for two tautomeric forms of 5-substituted creatinines indicate that the mechanism of the substituent influence in both tautomers for the investigated compounds appears to be analogous. We can predict that in solution this accepting inductive effect of substituent groups does not significantly influence the structure of creatinine molecule in solution. The analysis of coupling constants for 5-substituted creatinines gives information about conformation of the investigated molecules in solution.     

Manifestation of microgel-like particles of styrene-ethylene dimethacrylate copolymers in solution in 1H and 13C NMR spectra

From the integrated intensities of ¹H NMR bands it has been found that in solutions of styrene (St)-ethylene dimethacrylate (EDMA) copolymers, a considerable part of the monomer units do not show directly in high-resolution ¹H NMR spectra and it is suggested that these monomer units form compact structures, probably acting as cores of microgel-like particles. In ¹³C NMR spectra all monomer units are shown, including those which are part of the compact microgel structures. From a comparison of ¹H NMR spectra with other analytical methods (elemental analysis, infrared spectra) it follows that the composition of the copolymer in the core of the microgel is the same as the overall composition of the copolymer. The content of the compact structures in the microgel increases with the content of the EDMA component. The results are discussed from the point of view of structural features and of the motional restrictions of the St/EDMA copolymers in CCl₄ solution. The consequences for ¹H NMR analysis of copolymer composition are also discussed.     

1H and 13C NMR spectra of Strychnos alkaloids: Selected NMR updates

The PBE0/pcSseg-2//pcseg-2 calculations of ¹H and ¹³C NMR chemical shifts were performed for a classical series of 12 Strychnos alkaloids (except for the earlier studied parent strychnine), namely akuammicine, isostrychnine, rosibiline, tsilanine, spermostrychnine, diaboline, cyclostrychnine, henningsamide, strychnosilidine, strychnobrasiline, holstiine, and icajine. It was found that the calculated ¹H and ¹³C NMR chemical shifts show markedly good correlations with available experimental data, as characterized by a mean absolute error of 0.22 ppm for the range of 8 ppm for protons and 1.97 ppm for the range of 180 ppm for carbons. Complementarily, the present results provide essential NMR update and fill a gap in the NMR data of this distinguished group of vitally important natural products.     

1H, 13C and 15N NMR studies on adducts formation of rhodium(II) tetraacylates with some azoles in CDCl3 solution

Adduct formations of rhodium(II) tetraacetate and tetratrifluoroacetate with some 1H-imidazoles, oxazoles, thiazoles, 1H-pyrazoles and isoxazole have been investigated by the use of 1H, 13C, 15N NMR and electronic absorption spectroscopy (VIS) in the visible range. Azoles tend to form axial adducts containing rhodium(II) tetraacylates bonded via nitrogen atom. Bulky substituents close to the nitrogen atom prevent the Rh--N bond formation, and in several cases switch over the binding site to the oxygen or sulphur atoms. The (15)N adduct formation shift Deltadelta(15N) (Deltadelta = delta(adduct) - delta(ligand)) varied from ca - 40 to - 70 ppm for the nitrogen atom involved in complexation, and of a few parts per million only, from ca - 6 to 3 ppm, for the non-bonded nitrogen atom within the same molecule. The Deltadelta(1H) values do not exceed one ppm; Deltadelta(13C) ranges from - 1 to 6 ppm. Various complexation modes have been proved by electronic absorption spectroscopy in the visible region (VIS). For comparison purposes, some adducts of pyridine, thiophene and furan derivatives have been measured as well. The experimental findings were compared with calculated chemical shifts, obtained by means of DFT B3LYP method, using 6-311 + G(2d,p), 6-31(d)/LanL2DZ and 6-311G(d,p) basis set.     

1H and13C NMR spectra of C- and N-substituted oxazolidines

An interrelationship between the structure of oxazolidines and the character of their¹H and¹³C NMR spectra was ascertained, and the most characteristic signals of the individual groups, which make it possible to establish the structure of the investigated compounds, were found.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 900–903, July, 1982.     

Conformational distributions of N-acetyl-L-proline N-methylamide in CDCl3 solution studied by NMR and IR spectra

The amide proton NMR chemical shifts have been widely used for the determination of the population fractions of hydrogen bonding states in peptides. However, in such works the determination of the limiting chemical shift for each hydrogen bonding state is quite problematic. In our previous paper, we derived the expression for the limiting chemical shift as a function of IR band intensity and chemical shift, and then determined the values of the limiting chemical shifts at various temperatures. In the present study, the method was improved, and was applied to conformational studies of N-acetyl-L-proline N-methylamide (APM) in CDCl₃ solution. The population fractions obtained led to thermodynamic quantities of APM for both intra- and intermolecular hydrogen bondings, and also to the complete interpretation of the temperature dependence of the amide proton resonance.     

1H and 13C NMR spectra of condensed benzimidazole and imidazobenzodiazepines

Benzimidazoles are heterocyclic compounds that have awakened great interest during the last few years because of their proven biological activity as antiviral, antimicrobial, and antitumoral agents. For this reason, the development of a systematic NMR study of condensed benzimidazole compounds constitutes a significant tool in understanding the molecular dynamics and the structural parameters that govern their behavior. The ¹H and ¹³C NMR spectra of new imidazobenzodiazepines were investigated. Based on the study of NMR chemical shifts, we discuss the environmental effect of the nucleus ¹³C. The correlation ¹H–¹³C proved to be a useful method for distinguishing the assignment of carbon.