NMR Spectroscopic Properties Research Articles

A Water-Soluble Synthetic Bilirubin with Carboxyl Groups Replaced by Sulfonyl Moieties

The first symmetrical bilirubin analog with CO2H groups replaced by SO3H, 8,12-bis-(2-sulfo-ethyl)-3,17-diethyl-2,7,13,18-tetramethyl-(10H,21H,23H,24H)-bilin-1,19-dione, was synthesized from methyl (2,4-dimethyl-5-ethoxycarbonyl-1H-pyrrol-3-yl) acetate in nine steps via the sulfonic acid analog of xanthobilirubic acid (XBR) and isolated as its disodium salt. The sulfonic acid group was introduced at an early stage of the synthesis by reaction of an intermediate, ethyl 4-(2-bromoethyl)-3,5-dimethyl-1H-pyrrole-2-carboxylate, with sodium sulfite. The disodium bilirubin disulfonate exhibits NMR spectroscopic properties rather similar to those of the parent carboxylic acid, mesobilirubin-XIIIα; however, its UV/Vis spectra are blue-shifted and broadened relative to those of the parent compound. Like mesobilirubin, the disulfonate displays a positive exciton chirality circular dichroism spectrum, albeit with weaker Cotton effects, in a buffered aqueous solution (pH = 7.4) containing a 2:1 molar ratio of human serum albumin.

Formation, isolation, spectroscopic properties, and calculated properties of some isomers of C(60)H(36).

Isomers of C(60)H(36) and He@C(60)H(36) have been synthesized by the Birch or dihydroanthracene reduction of C(60) and isolated by preparative high-pressure liquid chromatography. (3)He, (13)C, and (1)H NMR spectroscopic properties were then determined. A comparison of experimental chemical shifts against those computed using density functional theory (B3LYP) with polarized triple- and double-zeta basis sets for He and C,H, respectively, allowed provisional assignment of structure for several isomers to be made. Theoretical calculations have also been carried out to identify low-energy structures. The transfer hydrogenation method using dihydroanthracene gives a major C(60)H(36) isomer and a minor C(60)H(36) isomer with C(3) symmetry as determined by the (13)C NMR spectrum of C(60)H(36) and the (3)He NMR spectrum of the corresponding sample of (3)He@C(60)H(36). In view of the HPLC retention times and the (3)He chemical shifts observed for the Birch and dihydroanthracene reduction products, the two isomers generated by the latter procedure can be only minor isomers of the Birch reduction. A significant energy barrier apparently exists in the dihydroanthracene reduction of C(60) for the conversion of the C(3) and C(1) symmetry isomers of C(60)H(36) to the T symmetry isomer previously predicted by many calculations to be among the most stable C(60)H(36) isomers. Many of the (1)H NMR signals exhibited by C(60)H(36) (and C(60)H(18), previously reported) are unusually deshielded compared to "ordinary" organic compounds, presumably because the unusual structures of C(60)H(36) and C(60)H(18) result in chemical shift tensors with one or more unusual principal values. Calculations clearly show a relationship between exceptionally deshielded protons beta to a benzene ring in C(60)H(18) and C(60)H(36) and relatively long C-C bonds associated with these protons. The additional information obtained from 1D and 2D (1)H NMR spectra obtained at ultrahigh field strengths (up to 900 MHz) will serve as a critical test of chemical shifts to be obtained from future calculations on different C(60)H(36) isomers.

Synthesis, 183W NMR spectroscopic characterization and properties of trisubstituted heteropolytungstates containing Group 3A elements

The heteropolytungstates α,β-K a H b XW 9M 3O 37(H 2O) 3· nH 2O (X=Si,Ge; M=Al, Ga, In, a+ b=7) are reported. All their 183W NMR spectra consist of two lines with an intensity ratio 2:1, as expected for the C 3 v structure of trisubstituted Aα, Aβ-Keggin anions. They have characteristic patterns of 183W NMR chemical shifts: δ belt W> δ cap W, Δ= δ belt− δ cap>0 and Δ α isomer >Δ β isomer. In addition, the chemical shifts of tungstosilicates shift 15±5 ppm upfield with respect to tungstogermanates, probably resulting from the different ionic radii of silicon and germanium.

Synthesis and metabolism of the first thia-bilirubin.

A symmetrical C(10)-thiabilirubin analogue, 8,12-bis(2-carboxyethyl)-2,3,17,18-tetraethyl-7,13-dimethyl-10-thia-(21H,23H,24H)-bilin-1,19-dione (1), was synthesized from 8-(2-carboxyethyl)-2,3-diethyl-7-methyl-10H-dipyrrin-1-one in one step by reaction with sulfur dichloride. The thia-rubin exhibited the expected IR, UV-vis, and NMR spectroscopic properties, which are rather similar to those of mesobilirubin-XIIIalpha. Like bilirubin and mesobilirubin, 1 adopts an intramolecularly hydrogen-bonded conformation, shaped like a ridge-tile but with a steeper pitch. The longer C-S bond lengths and smaller bond angles at C-S-C, as compared to C-CH(2)-C, lead to an interplanar angle between the two dipyrrinones of only 74 degrees -or considerably less than that of bilirubin (approximately 100 degrees). On normal- and reversed-phase chromatography, 1 is substantially less polar than bilirubin. Despite this conformational distortion, 1 is metabolized in normal rats to acyl glucuronides, which are secreted into bile. In mutant (Gunn) rats lacking bilirubin glucuronosyl transferase, 1 (like bilirubin) was not excreted in bile.

A new class of triazepine–ruthenium(II) complexes: synthesis, crystal structure and NMR spectroscopic properties

Two unprecedented three-dimensional ruthenium(II) complexes I and II derived from 2-methyl-5-oxo-7-phenyl-3-thioxo-3,4,5,6-tetrahydro-2 H-1,2,4-triazepine (HTAZO) and 2-methyl-7-phenyl-3,5-dithioxo-3,4,5,6-tetrahydro-2 H-1,2,4-triazepine (H 2TAZS) have been prepared by the reaction of these triazepines with [Ru( p-cymene)Cl 2] 2 in the presence of triethylamine. NMR spectroscopic and X-ray diffraction studies of the structures of the resulting complexes reveal different behavior of HTAZO and H 2TAZS in the coordination process.

Correlations between structural, NMR and IR spectroscopic properties ofN-methylacetamide

Bond lengths, quadrupole coupling constants, chemical shifts and vibrational frequencies are important probes of hydrogen bonding. This was previously demonstrated for liquid N-methylacetamide (NMA) showing that cooperativity and non-additive contributions of hydrogen bonds play a significant role. The spectroscopic properties were calculated by standard ab initio methods in combination with a quantum cluster equilibrium (QCE) model and compared with measured data from NMR and IR spectroscopy. We have now extended the QCE model to larger molecular clusters and obtained better agreement between calculated and measured liquid-phase properties over large temperature ranges. The obtained linear correlations between spectroscopic properties and bond lengths and between different spectroscopic properties allow predictions for the gas- and the solid-phase values. The results can be used as a prediction tool for larger biomolecular structures where some experimental methods cannot be used or are not accurate enough. Copyright © 2001 John Wiley & Sons, Ltd.

Microstructure and morphology of polyphenylacetylene prepared in compressed carbon dioxide

Polyphenylacetylene was prepared by transition metal catalysis in compressed (liquid and supercritical) CO2. Surface morphology, IR and NMR spectroscopic properties of the resulting materials are discussed in terms of the microstructure of polymers. Copyright © 2001 John Wiley & Sons, Ltd.

New rearranged limonoids from Harrisonia perforata.

Two new rearranged limonoids, named haperforine A (1) and haperforine E (2), were isolated from a sample of Harrisonia perforata leaves collected in Center Vietnam and their structures determined by X-ray diffraction analysis. The structure of a minor compound was established as 12-desacetylhaperforine A (3) by chemical correlation. Their NMR and mass spectroscopic properties are reported.

A Study on the Spectra Characterization of Ruthenium(Ii) Complexes

A series of Ru(II) complexes have been synthesized, and their electronic spectra and NMR spectroscopy properties were characterized. the chemical shifts of aromatic protons of [Ru(bpy)3] (PF6)2, [Ru(phen)3](ClO4)2 and [Ru(bqdi)3](PF6) move downfield, but the resonance peaks of cis-Ru(bpy)2Cl2 shift upfield. Within the visible spectra of the ruthenium(II) complexes appear a relatively high oscillator strength which is referred to as the π(Ru)→* (ligands) transition.

The Solid State Conformation of Diaryl Ditellurides and Diselenides: The Crystal and Molecular Structures of (C4H3E2)2E'2 (E = O, S; E' = Te, Se)

The crystal and molecular structures of dithienyl ditelluride (C4H3S)2Te2 (1), difuryl ditelluride (C4H3O)2Te2 (2), dithienyl diselenide (C4H3S)2Se2 (3), and difuryl diselenide (C4H3O)2Se2 (4) are reported in this paper and compared to those of other simple diaryl ditellurides and diselenides. The chalcogen-chajcogen bonds exhibit approximately single bond lengths [Te-Te = 2.7337(8) and 2.7240(4) Å in 1 and 2, respectively; Se-Se = 2.357(1) and 2.368(2) Å in 3 and 4, respectively], as do the chalcogen-carbon bond lengths [Te-C = 2.095(9) - 2.104(6) in 1 and 2.091(6) - 2.105(9) Å in 2; Se-C = 1.87(1) - 1.90(1) Å in 3 and 1.887(8) - 1.897(10) Å in 4]. The aromatic rings are disordered. The dihedral angles C-E-E-C range from 79(2) to 96(1)° are consistent with the concept of minimized p lone-pair repulsion of adjacent chalcogen atoms. The dependence of molecular parameters on the angle between the aromatic rings and the chalcogen-chalcogen bonds follow trends established previously for aromatic disulfides. Though the bond parameters and conformations of 1 - 4 are similar, the packing of the molecules is different. The two ditellurides 1 and 2 show short Te···Te contacts (3.900 - 4.002 Å in 1 and 4.060 - 4.172 Å in 2). The two diselenides 3 and 4 do not exhibit close chalcogen-chalcogen interactions. The NMR spectroscopic properties of 1 - 4 are discussed.

Synthesis, Multinuclear (1H, 13C and 17O ) Magnetic Resonance Spectroscopy and Conformational Analysis of Some Substituted Aryl Naphthoates

The synthesis of 16 title compounds and their NMR spectroscopic properties is described. The spectra reveal evidences of the preferred conformation (acetyl group orientation and non-coplanarity) of the aroyl moieties.

1-Metallacyclopropene Complexes and η1-Vinyl Complexes Containing the Cp*W(NO) Fragment

The solid-state molecular structure of Cp*W(NO)(CH2SiMe3)(η2-CPhCH2) reveals that the vinyl ligand in this complex exists in a distorted form in the solid state that cannot be readily described by either of the classic η1-vinyl or 1-metallacyclopropene limiting structures, by comparison to other crystallographically characterized vinyl complexes reported in the literature. However, the NMR parameters for the CPhCH2 fragment in this complex are characteristic of those of a 1-metallacyclopropene unit. In addition to these studies, a series of vinyl-containing species of the general formulas Cp*W(NO)(η2-CPhCH2)(X) and Cp*W(NO)(η1-CPhCH2)(LX) (X = Cl, OTf; LX = O2CPh, NHtBu, (PPh3)(H)) has been prepared, and the solid-state metrical parameters and solution NMR spectroscopic properties of these complexes have been examined and compared to those of other vinyl-containing complexes reported in the literature. It has been found that the nature of the tungsten−vinyl interaction in these compounds is dependent upon...

Tantalum μ-Alkylidyne Compounds Containing o-Phenyl- and o-(1-Naphthyl)phenoxides: Probing Molecular Structure and Dynamics

The new o-(1-naphthyl)phenols 2-(1-naphthyl)-4,6-di-tert-butylphenol, 2,6-bis(1-naphthyl)phenol, 2,6-bis(1-naphthyl)-3,5-dialkylphenol (alkyl = Ph, Me, But), and 2-(1-naphthyl)-3,5,6-triphenylphenol have been synthesized. The reaction of these phenols and their o-phenyl counterparts with the compound [Ta2(μ-CSiMe3)2(CH2SiMe3)4] has been investigated. This reaction produces the monosubstitution products [(ArO)(Me3SiCH2)Ta(μ-CSiMe3)2Ta(CH2SiMe3)2] at rates which are strongly dependent on the nature of the phenol substituents. The NMR spectroscopic properties of the resulting derivatives can be used to probe the phenoxide structure. Nonchiral phenoxides yield singlets for the CH2SiMe3 methylene protons and one set of μ-CSiMe3 resonances, whereas the presence of a chiral phenoxide generates diastereotopic CH2SiMe3 protons and nonequivalent μ-CSiMe3 groups. The solid-state structure of the 2-(1-naphthyl)-3,5,6-triphenylphenoxide and 2,6-bis(1-naphthyl)phenoxide derivatives shows that the 1,3-dimetallacyclobuta...

Synthesis and structure of niobium and tantalum derivatives of bis(dicyclohexylphosphino)methane (dcpm)

The sodium amalgam reduction (2 Na per M) of the Group 5 metal chlorides [M 2Cl 10] (M=Nb, Ta) in the presence of bis(dicyclohexylphosphino)methane (dcpm) leads to the binuclear compounds [(dcpm)Cl 2M(μ 2-Cl) 2MCl 2(dcpm)] (M=Nb, 1; Ta, 2). Solution NMR spectroscopic properties of 1 and 2 indicate that the dcpm ligand does not bridge (binucleate) the di-metal unit but is chelated to a single metal center. A single crystal X-ray diffraction study of 1 confirms this and shows two independent molecules both with an edge shared bis-octahedral geometry with NbNb distances of 2.738(1) and 2.749(1) Å. The addition of dcpm to the tantalum trichloride [Ta(OC 6H 3Pr i 2-2,6) 2Cl 3] 2 initially leads to the adduct cis- mer-[Ta(OC 6H 3Pr i 2-2,6) 2Cl 3(dcpm)] ( 3). The molecular structure of 3 is found to contain an η 1-bound dcpm ligand. In the 31P NMR spectrum of 3 well resolved doublets are present for the coordinated and ‘dangling’ phosphorus atoms. The sodium amalgam reduction of 3 in hydrocarbon solvents does not lead to any isolable binuclear compounds. Instead the reaction leads to the compound [Ta(OC 6H 3Pr i-η 2-CMeCH 2)Cl(dcpm)] ( 4). Compound 4 contains an aryloxide ligand chelated to the metal via an η 2-interaction with a vinyl group formed by the dehydrogenation of an ortho-isopropyl group. The structural parameters are consistent with a metallacyclopropane bonding description for this interaction.

The Biogenesis of β-N-(γ-Glutamyl)-4-Hydroxymethylphenylhydrazine (Agaritine) in Agaricus Bisporus in Honour of Professor G. H. Neil Towers 75th Birthday

According to the biogenetic scheme of Schütte etal. (An. Quim., 1972, 68, 899), agaritine [AG; β-N-(γ-glutamyl)-4-hydroxymethylphenylhydrazine (HMPH)], a constituent of the fruit body of the common mushroom Agaricus bisporus, is generally held to be a shikimate-derived metabolite. A critical evaluation of the methodological basis of this tenet showed it is not supported by the experimental data presented. A major doubt concerns the conditions used for hydrolysis of the hydrazide bond; therefore, two derivatives of HMPH, 2- and 4-nitrobenzaldehyde hydrazones, were synthesized as reference compounds for the assessment of the desglutamyl product. The UV-, IR- and 1H NMR spectroscopic properties of the two new substances are listed. Using (i) the established shikimate-derived metabolite γ-glutaminyl-4-hydroxybenzene, which co-occurs with AG, as the positive control, (ii) the shikimate-chorismate pathway inhibitor ‘glyphosate’ as a tool, and (iii) complementary results from physiological experiments, it was demonstrated that there is no de novo synthesis of the desglutamyl moiety of AG in the fruit body. The likely site of AG synthesis is the vegetative hyphae in contact with the wheat straw compost. A speculative scheme is presented for the assembly of AG, which postulates an exogenous origin of both the aryl and the hydrazide moieties of this, resulting, respectively, from the breakdown of lignin by the fungus and the diazotrophic activity of a bacterial commensal in the substratum.

A tetranuclear silver complex with dppm and i-mnt ligands. Synthesis and structural characterization of [Ag 4( μ-dppm) 4( μ4 i-mnt) 2] · 0.5 DMF (i-mnt  2,2-dicyano-1,1-ethylenedithiopate; dppm  bis(diphenylphosphino)methane)

The reaction of [Ag(dppm) (NO 3)] 2 ( 1) with potassim i-mnt  2,2-dicyano-1,1-ethylenediothiolate; dppm  bis (diphenylphosphino)methane) in DMF at room temperature gave rise to the complex [Ag 4( μ-dppm) 4( μ 4-S 2C=C(CN) 2) 2] ( 2). The crystal structure of 2 has been determined by single crystal X-ray diffraction analysis. 2 is a tetranuclear complex with a silver-silver separation of 3.376(2) Å and the four silver atoms form a distorted square plane bridged by four dppm and two i-mnt ligands. Each silver atom is coordinated by two phosphorus and two sulfur atoms in a distorted tetrahedral environment. The IR, 1H and 31P NMR spectroscopic properties of 2 have also been investigated.

Synthesis and X-ray Crystal Structure of a Triple-Stranded Helical Supramolecular Complex Formed between Tris(3-(pyridin-2-yl)pyrazole)ruthenium(II) and Copper(I).

Reaction between [Ru(py-pzH)3](ClO4)2 (where py-pzH = 3-(pyridin-2-yl)pyrazole) and Cu(II) or Cu(I) in methanol, in the presence of excess NEt3, affords the triple-strand helical supramolecular {[Ru(py-pz)3]2Cu3}(ClO4). The X-ray crystal structure and 1H NMR and electronic spectroscopic properties of {[Ru(py-pz)3]2Cu3}(ClO4) are reported.

Synthesis and nuclear magnetic resonance spectroscopic properties of some acetylenic tellura fatty acid esters

Five positional isomers of acetylenic tellura stearate ( 1– 5) have been synthesized by three different routes. The number of methylene groups located between the acetylenic system and the tellurium metal varies from 0 to 4. The 1H and 13C NMR spectroscopic properties have been studied. The tellurium atom induces strong deshielding effects on the adjacent methylene protons, which in combination with the deshielding effects of the acetylenic system allows most of the methylene groups between the tellurium and the triple bond to be identified by 1H NMR spectroscopic analysis. The tellurium causes a very strong shielding effect (ca. −27.1 ppm) on the carbon shift of the adjacent α-methylene carbon atom, but weak deshielding effects on the β-(ca. +2.6 ppm) and γ-(ca. +2.3 ppm) methylene carbon atoms. Carbon shifts of methylene carbon atoms, especially those which are located between the tellurium atom and the triple bond, are found very much upfield ( δ C 0.65–4.81) and in one case in the negative region ( δ C−17.95) of the 13C NMR spectrum. Most of the signals of the carbon nuclei of these analogue have been identified and from the results of these analyses the number of methylene groups between the acetylenic system and the tellurium atom can be determined.

Syntheses, structures and spectroscopic properties of [Ag(dppm)(O 2CCH 2Ph)] 2 and [Ag 2(dppm) 3](NO 3) 2·3H 2O

The reaction of [Ag(dppm)(NO 3] 2 with sodium phenylacetate and dppm in THF at room temperature gave rise to the silver complexes [Ag(dppm)(O 2CCH 2Ph)] 2 ( 1) and [Ag 2(dppm) 3](NO 3) 2 ( 2), respectively. Their crystal structures have been determined by single crystal X-ray diffraction analysis. Complex 1 is binuclear with a silver-silver separation of 3.080 Å and bridged by two dppm ligands. The cation in complex 2 possesses a Ag 2P 6 core with AgAg distance of 2.987 Å and the silver atoms are each coordinated by three phosphorus atoms in an ideal trigonal-planar environment. Their IR, Raman, 1H and 31P NMR spectroscopic properties are also reported.

Synthesis of the First Fluorinated Bilirubin

A symmetrical difluorinated bilirubin analog, 8,12-bis(2-carboxy-2-fluoroethyl)-3,17-diethyl-2,7,13,18-tetramethyl-10H,21H,23H,24H-biline-1,19-dione (9), was synthesized from methyl 3-[2,4-dimethyl-5-(methoxycarbonyl)-1H-pyrrol-3-yl] propionate (1) in nine steps. Fluorine was introduced by reaction of an intermediate methyl 3-[1-(tert-butoxycarbonyl)-2,4-dimethyl-5-(methoxycarbonyl)-1H-pyrrol-3-yl]-2-hydroxypropionate (5), with (diethylamino)sulfur trifluoride (DAST). The fluorinated rubin exhibited the expected IR, UV-vis, and NMR spectroscopic properties, similar to those of the unfluorinated parent, mesobilirubin XIIIalpha. However, the solubility properties unexpectedly differed, with the fluorinated rubin being less soluble in organic solvents than its parent. While this phenomenon may be attributed to the much increased acidity of the carboxylic acid hydrogens in 9, it probably also arises from less effective intramolecular hydrogen bonding due to a decreased basicity of the propionic acid carbonyl groups.