The Composition of Keto Aldoses in Aqueous Solution as Determined by NMR Spectroscopy

Keto aldoses usually form complex mixtures of equilibrating isomers in solution. This is due to the two different positions that may be used for ring closure in dicarbonyl sugars. The composition of various 2‐keto aldoses 1 – 5 and 8 , the 3‐keto aldose 2‐deoxy‐D ‐erythro‐hexos‐3‐ulose ( 9 ), and the ketose 1‐deoxy‐D ‐ribulose ( 10 ) in aqueous solution has been determined by NMR spectroscopy. The investigated keto aldoses form equilibria containing three to fifteen isomers. Among various furanose and pyranose ring structures stemming from 1,4‐, 1,5‐, 2,5‐, and 2,6‐cyclization, bicyclic forms were also found in several cases. The 2‐keto aldoses mainly exist as hydrated isomers in H₂O. Therefore, these forms and their proportions were compared to forms found in two homomorphous aldoses and one homomorphous ketose as model compounds. Besides the NMR data, also the composition of the 2‐keto aldoses agreed with the average of forms found in the model compounds, a finding that might eventually be useful for deducing the composition of other keto aldoses.     

The Isomeric Composition of D-Xylo-hexos-5-ulose (5-Keto-glucose) in Aqueous Solution

Abstract

1,2-O-Isopropylidene-α-D-xylo-hexofuranos-5-ulose (2) was deprotected in aqueous acid solution to give a mixture of at least six isomeric forms and one anhydro form of the parent ketoaldohexose, D-xylo-hexos-5-ulose (3), commonly referred to as 5-keto-glucose. Structural assignment of each form was made based on high field ¹H and ¹³C NMR studies of the mixture in aqueous (D₂O) solution. The dominant isomeric form of 3 was observed to have the pyranose structure 1R,5R-D-xlyo-hexo-pyranos-5-ulose (3a, 67 %) with the next most abundant form being an anhydro structure, 1S,5S-l,6-anhydro-D-xylo-hexopyranos-5-ulose (3c, 18 %). Included among the other isomers were the a and β-1,4-furanose (3d, 3e) and 1-aldehydrol β-5,2-furanose (3f) structures. The isomer present in least amount (3g, > 1 %) is assigned as the α-anomer of 3f. Experimentally determined J_C-1,H-1 values were useful in support of assigned isomer structures.     

1H NMR Analyses of Rotameric Distribution of C5-C6 bonds of D-Glucopyranoses in Solution

Abstract

¹H NMR signals of H-6proR and H-6proS protons of D-glucoses and their per-O-acylated (acetyl and benzoyl) derivatives were unambiguously assigned by chiral deuteration at the C-6 position. The J_H5,H-6proR and J_H5,H-6proR values thus obtained enabled us to calculate the rotameric distributions of gg, gt and tg conformers. For the calculations, conventional equations (A and B) and novel equations accounting for possible departure of the three conformers from perfect staggering, were employed. The results showed that D-glucoses irrespective of solvents and protecting groups were predominant in two conformers gg and gt in an approximate ratio of 60 and 40, respectively, with a negligibly low population of the tg conformer. These results were in complete accordance with the statistical study of X-ray data of D-glucoses.     

Protonation of pyrimidotriazinediones by1H and13C NMR spectroscopy

On the basis of an analysis of the changes in the chemical shifts of the signals in the¹H and¹³C NMR spectra on the pyrimidotriazinedione and trifluoric acid concentrations in CDCl₃ it was established that the protonation of rheumycin and fervenulin takes place at the N(₂) atom, whereas the protonation of isofervenulin takes place competitively at the N(₁), N(₂), and O(₆) atoms. The equilibrium constants of the investigated protonation processes were measured.A study of the chemical peculiarities of the behavior of Ia, b in aqueous acidic media (H₂O-HCl, D₂O-DCl) was described in [6].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1532–1538, November, 1988.     

Cyanocuprates as Homo-dimer in Etheral Solution:1H,6Li and 1H,1H Distances Information by NMR

Despite of the wide application of organocuprates in many areas of organic synthesis, little is known about their detailed structures in solution. Recently we found by NMR that organocuprates in etheral solution exist as an equilibrium between solvent separated ion pairs (SSIPs) and contact ion pairs (CIPs) with the preference of the equilibrium mainly dependent of the solvent properties, and the CIPs as the reactive species. We focus here on ¹H, ⁶Li and ¹H, ¹H distances investigation by NMR spectroscopy of Me₂CuLi(l) and Me₂CuLi*LiCN (1*LiCN) in Et₂O as models for the structure of salt-free and salt-containing CIPs in solution.     

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.     

Structural analysis of 1-vinylbenzazoles by 1H and 13C NMR spectroscopy

Analysis of ¹H and ¹³C NMR spectral parameters for 1-vinylbenzazoles has shown that the vinyl group has a predominantly trans orientation with respect to the condensed benzene ring. Additional evidence is given for a long range effect of the nitrogen lone pair electrons on the one bond ¹³C-¹H and ¹H-¹H spin-spin couplings and on the ¹H chemical shifts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 499–501, April, 1988.     

A 1H and 13C NMR and UV Study of the State of Hydroxyacetone in Aqueous Solutions

The state of hydroxyacetone in neutral aqueous solutions was studied by ¹H and ¹³C NMR and UV spectroscopy. In the concentration range 0.1-1.41 M, 96-98% of hydroxyacetone exists in the carbonyl form. The content of the hydrated form of hydroxyacetone is 2-4%. No dimeric and polymeric species were detected.     

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.     

Aromatic imine stereochemistry as studied by 13C and 1H NMR of 15N-enriched materials

A series of thirteen ¹⁵N-enriched N-aryl imines derived from benzaldehydes and acetophenones have been prepared and examined by ¹³C and ¹H NMR. Preferred conformations of the C-arvl and N-aryl rings have been deduced from ¹³C chemical shifts and ¹³C-¹⁵N couplings. Evidence for steric inhibition of resonance in O-alkylated materials is presented. Relative signs of ¹J(CN) and ²J(CCN) have been determined in some compounds. An E: Z interconversion barrier of 21.6 kcal mol^?1 has been obtained from ¹H NMR coalescence data.     

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.     

A 13C and 1H NMR analysis of perfumes

Composition of a series of formulations used in Russia for production of various perfumes, among them car air fresheners, was studied by ¹³C and ¹H NMR. The main components were identified, approximate compositions of several perfumes were determined, and spectral data are given. These spectral data can be used for prompt analysis for composition of commercial odorants with the aim of monitoring their quality and hygienic characteristics.     

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.     

1H NMR Study of Heteroassociation of Daunomycin and Propidium Iodide in Aqueous Solution

Heteroassociation of an anthracycline antibiotic Daunomycin (DAU) and phenanthridine dye Propidium iodide (PI) in aqueous solution was studied by ¹H NMR spectroscopy. The complex PI-DAU is stabilized mainly by dispersion van der Waals interactions and hydrogen bond between the 3(8)-amino group of the dye and 9-acetyl group of DAU. This conclusion follows from comparison of parameters of DAU-PI heteroassociation and complex formation of DAU with aromatic dyes, Proflavine and Ethidium bromide, under the same conditions.     

NMR研究溶液中正十四烷基硫酸钠/正十四烷基聚氧乙烯醚(3)表面活性剂之间的相互作用

采用¹HNMR弛豫、自扩散系数和二维相敏(2DNOESY)实验研究了正十四烷基硫酸钠[n-CH₃(CH₂)₁₃OSO₃Na(STS)]和正十四烷基聚氧乙烯醚(3)[n-CH₃(CH₂)₁₃O(C₂H₄O)₃H(C₁₄E₃)]在溶液中的自聚集以及二者混合后的相互作用.结果表明,STS与C₁₄E₃混合后存在相互作用,并形成混合胶束;弛豫实验表明,混合胶束中STS疏水链质子运动更加受阻,C₁₄E₃的α-(4″)和β-CH₂(3″)处链堆积紧密.C₁₄E₃的亲水端(CH₂CH₂0)₃链卷曲紧贴在疏水壳表面外链堆积较紧密处.自扩散系数测量表明,混合胶束比单一阴离子表面活性剂形成的胶束大.单一非离子型胶束和混合胶束的亲水端(CH₂CH₂0)₃(5″)链构成相应较软和松散的外壳.单一C₁₄E₃在极性溶剂氯仿溶液中,质子运动比在水中自由度大,但2DNOESY谱中出现了少量分子间的交叉峰,也可能形成了一些小的聚集体.     

1H NMR Analysis of Heteroassociation of Caffeine with Mitoxanthrone in Aqueous Solution

Heteroassociation of caffeine (CAF) with the antibiotic mitoxanthrone (novatrone, NOV) in aqueous solution was studied by one-dimensional (1D) and two-dimensional (2D) ¹H NMR spectroscopy (500 MHz). The concentration and temperature dependences of the proton chemical shifts of the molecules in aqueous solution have been measured. The equilibrium constants of heteroassociation between CAF and NOV and the limiting proton chemical shifts of the aromatic ligands of the associates have been determined. The most plausible structure of the 1:1 CAF–NOV heterocomplex in aqueous solution was inferred from the calculated values of the induced proton chemical shifts and quantum-mechanical screening curves for CAF and NOV. The thermodynamic parameters of the formation of the CAF–NOV heterocomplex have been calculated. The relatively high heteroassociation constant (K = 256 ± 31 M^–1, T = 318 K), the positive value of entropy for heteroassociation [ S = 15.3 ± 4.0 J/(moleK)], and the structural features of the chromophore of the novatrone molecule indicate that hydrophobic interactions play a significant role in stabilization of the CAF–NOV heterocomplex.