Complete 1H Assignments Research Articles

Characterization of UDP amino sugars as major phosphocompounds in the hyperthermophilic archaeon Pyrococcus furiosus.

The archaeon Pyrococcus furiosus is a strictly anaerobic heterotroph that grows optimally at 100 degrees C by the fermentation of carbohydrates. It is known to contain high concentrations of novel intracellular solutes such as beta-mannosylglycerate and di-myo-inositol 1,1'-phosphate (DIP) (L. O. Martins and H. Santos, Appl. Environ. Microbiol. 61:3299-3303, 1995). Here, 31P nuclear magnetic resonance (NMR) spectroscopy was used to show that this organism also accumulates another type of phospho compound, as revealed by a major multiplet signal in the pyrophosphate region. The compounds were purified from cell extracts of P. furiosus by anion-exchange and gel filtration chromatographic procedures and were structurally analyzed by 1H, 13C, and 31P NMR spectroscopy. They were identified as two uridylated amino sugars, UDP N-acetylglucosamine and UDP N-acetylgalactosamine. Unambiguous characterizations and complete assignments of 1H and 13C resonances from such sugars have not been previously reported. In vitro 31P NMR spectroscopic analyses showed that, in contrast to DIP, which is maintained at a constant intracellular concentration (approximately 32 mM) throughout the growth phase of P. furiosus, the UDP amino sugars accumulated (to approximately 14 mM) only during the late log phase. The possible biochemical roles of these compounds in P. furiosus are discussed.

Complete Assignment of1H and13C NMR Spectra and Conformational Analysis of Thioamide Cannabinoids

The complete assignment of the 1H and 13C NMR spectra of two carbothioamide- substituted meroterpenes is presented. Resonance assignments were achieved by the use of one- and two- dimensional NMR, NOED, selective decoupling measurements and the deuterium isotope effect on the 13C chemical shifts. Six-membered ring conformations were determined by analysis of proton spin coupling constants with the aid of spectral simulations in conjunction with molecular mechanics calculations and equations correlating coupling constants and dihedral angles. The anisotropy effect of benzene rings was used for structural assignments.

Regio and stereo selective hydrogenation of 17-Substituted 13β-ethyl-11β-hydroxy-gona-4,9-dien-3-ones and NMR study

Selective hydrogenation of 17-Substituted 13β-ethyl-11β-hydroxy-gona-4,9-dien-3-ones (3a,b) in Pd(0)/SrCO3-pyridine media gives the corresponding 11β-hydroxy-gon-4-en-3-ones (4a,b). The complete assignments of 1H and 13C NMR spectra of the main products (4a,b) are made by one and two dimensional NMR techniques, such as J-MOD or ATP, 1H-1H COSY, HETCOR and COLOC, with the aid of the templates for recognition of proton signals suggested by Kirk and co-workers. The substituent effects of 10-CH3, 11β-OH and 18-CH3 in 4-en-3-one steroids are summarised from model compounds and the good correlation is found between experimental and calculated carbon-13 chemical shifts of 4a,b and 15. The high stereo selectivity is due to steric hindrance of substituents at β-side. The solvent effects are also discussed

Stereochemicai study of 7-aryl-1,7,8,8a-tetrahydro-3(2H)indolizinones by1H and13C NMR

Stereochemistry of 7-aryl-1,7,8,8a-tetrahydro-3(2H)-indolizinones was studied by1H and13C NMR. Complete assignment of1H NMR signals and analysis of1H-1H coupling constants were performed using the iterative PANIC program. Values of3J6,7,3J7,8endo, and4J5,7 allow one to unambiguously identify the correspondingexo- andendo-stereoisomers. For stereoisomers with exo-orientation of H(7), complete assignment of13C NMR signals was performed on the basis of analysis of the13C-1H coupling constants using two dimensional heteronuclear shift-correlating spectroscopy.

Conformational analysis of c3′‐c8 connected biflavones

AbstractTwo biflavones isolated from Taxus cuspidata were identified with ginkgetin (1) and sciadopitysin (2) which belong to C3′‐C8 connected biflavones. The conformation of 2 in the solid state was determined by X‐ray analysis and the conformations of 1 and 2 in the liquid state were discussed using nmr techniques. Complete assignments of 1H and 13C nmr spectra about 1 were made on the basis of COSY, HMQC, HMBC and nOe experiments.

Prosapogenins from Dodonaea attenuata

AbstractSaponins have been extracted from the seed of Dodonaea attenuata and converted to prosapogenins by mild acid hydrolysis. Partially acetylated derivatives of the sapogenin, R1‐barrigenol, were characterized by extensive two dimensional nuclear magnetic resonance spectroscopy. The complete assignments of 1H and 13C resonances and nuclear Overhauser effects of these partly acetylated sapogenins has allowed a straightforward assignment of the structures of the prosapogenins, including the location of the individual ester groups and the presence of artefacts from the acidic hydrolysis conditions.

Complete 1H and 13C NMR assignments of two steroid 5, 6β‐epoxides using 1D TOCSY and 2D HMQC TOCSY experiments

AbstractThe complete assignments of 1H and 13C data for two steroid epoxides, 3β‐acetoxy‐5,6β‐epoxyandrostan‐17‐one and 3β‐acetoxy‐5,6β‐epoxycholestane, based on DEPT, 1H1H DQF COSY, HMQC, 1D TOCSY and 2D HMQC TOCSY sequences are described. Especially the 1D TOCSY and 2D HMQC TOCSY techniques were essential to the structure elucidation of theses steroids.

Triterpene caffeates from bark of Betula pubescens

Three new caffeic acid esters [3β,23-dihydroxy-olean-12-en-28-oic acid 3β-caffeate, 3β,23-dihydroxy-olean-12-en-28-oic acid 23-caffeate and 3β,23-dihydroxy-lup-20(29)-en-28-oic acid 3β-caffeate] of triterpene alcohols and another four known compounds of this type were isolated from the outer bark of Betula pubescens. Complete assignments of 1H and 13C NMR spectra of these compounds are given.

Synthesis and NMR Spectroscopic Investigation of a Macrocyclic Diphosphine Ligand and its nickel(II) and palladium(II) complexes

AbstractThe preparation of a macrocyclic diphosphine ligand 5 incorporating a binaphthyl unit and its NiII and PdII complexes, 6 and 7, is described. A complete assignment of 1H,‐ 13C‐, and 31P‐NMR data on the basis of 2D NMR spectroscopy (1H, 1H‐, 13C, 1H‐, 31P, 1H‐, 31P, 13C‐COSY) was possible for 5, and also – in part – for 6 and 7.

Absolute Structure of 2'-Desacetoxyaustrospicatine Established by X-Ray Analysis and Circular Dichroism Spectroscopy.

Three taxane diterpenes, taxinine (1), taxinine B (2), and 2'-desacetoxyaustrospicatin (3), have been isolated from Taxus cuspidata SIEB et ZUCC. The absolute stereostructure of 3 has been determined by a combination of X-ray analysis and circular dichroism (CD) spectroscopy. Complete assignments of 1H- and 13C-nuclear magnetic resonance (NMR) signals for 1 and 2 have been made on the basis of two-dimensional (2D) NMR techniques.

Application of two‐dimensional NMR to the structure determination of an unsymmetrical monosubstituted bisporphyrin

AbstractThe complete assignment of 1H and 13C data of an unsymmetrical monosubstitute bisporphyrin based on an extensive application of two‐dimensional 1H1H, 1H13C and 13C‐13C shift spectroscopy is described. The 1H1H shift correlation through dipolar interaction (2D NOESY) was essential to prove the connection of the alkyl fragments and to distinguish protons spatially close but belonging to different units. The additive structural increments method allowed the assignment of the quatenary carbons of tolyl residues.

NMR studies of oligosaccharides derived from hyaluronate: complete assignment of 1H and 13C NMR spectra of aqueous di- and tetra-saccharides, and comparison of chemical shifts for oligosaccharides of increasing degree of polymerisation

A series of oligosaccharides was prepared from hyaluronate by depolymerisation with bovine testicular hyaluronidase. Complete assignment of the 1H and 13C NMR spectra was obtained for the disaccharide, the tetrasaccharide, and the NaBH 4-treated tetrasaccharide, by using various 1D and 2D NMR methods. The 1H assignments for the tetrasaccharide differ from the incomplete data reported recently (ref. 11). The 13C NMR spectra of the aqueous di, tetra-, hexa-, and octa-saccharides of this series show that all resonances, apart from those subject to obvious end effects, have chemical shifts comparable to those of the corresponding resonances of hyaluronate in D 2O. The observed 13C chemical shifts suggests that cooperative intramolecular hydrogen bonds probably play a minor role in determining the conformation of hyaluronate in water.

Complete Assignment of 1H and 13C Nuclear Magnetic Resonance Chemical Shifts of β-1,2-Linked Mannooligosaccharides Isolated from the Phosphomannan of the Pathogenic Yeast Candida albicans NIH B-792 Strain

To confirm correctness of the previous assignment study of H-i protons of β-1,2-linked mannooligosaccharides provided by Shibata et al. (Biochemistry 31, 5680-5686, 1992), anotber type of nonempirical assignment of the H-1 signals of be same oligosaccharides was achieved by adopting a sequential NMR assignment method that combines two-dimensional 1H-13C correlated spectroscopy, two-dimensional 1H-1H correlated spectroscopy, and two-dimensional heteronuclear multiple-bond connectivity. Based on the above results, all of the 1H and most of the 13C signals in each oligosaccharide could also be assigned. The results of the proton assignment study provided sufficient evidence to confirm the correctness of that obtained in the previous H-1 proton assignment study. Furthermore, the existence of a regularity rule between the order of mannose units and its 1H and 13C chemical shifts has been revealed.

1H and 15N resonance assignments and secondary structure of the human thioredoxin C62A, C69A, C73A mutant.

The complete assignment of 1H and 15N backbone resonances and near-complete 1H side-chain resonance assignments have been obtained for the reduced form of a mutant of human thioredoxin (105 residues) in which the three non-active site cysteines have been substituted by alanines: C62A, C69A, C73A. The assignments were made primarily on the basis of three-dimensional 15N-separated nuclear Overhauser and Hartmann-Hahn spectroscopy, in conjunction with two-dimensional homonuclear and heteronuclear correlation experiments. Based on comparisons of short-range and interstrand nuclear Overhauser effects, patterns of amide exchange, and chemical-shift differences, the structure appears essentially unchanged from that of the previously determined solution structure of the native protein [Forman-Kay, J.D. et al. (1991) Biochemistry, 30, 2685-2698]. An assay for thioredoxin shows that the C62A, C69A, C73A mutant retains activity. The assignment of the spectrum for this mutant of human thioredoxin constitutes the basis for future studies aimed at comparing the details of the active-site conformation in the reduced and oxidized forms of the protein.

The Synthesis and NMR Study of 2,4-Diaryl-6-(fluoren-2-yl)pyridines

The reaction of 2-cinnamoylfluorene II with quaternary pyridinium salts IIIa, IIIb in the presence of ammonium acetate, gave 2-fluorenyl-2,6-diarylpyridines IV. The complete assignment of 1H and 13C resonances by 2D NMR methods is given.

Synthesis and characterization of platinum(II) and palladium(II) complexes with 2,5-dimethyl-4-hydroxypyrimidine

The binding of Pt(II) and Pd(II) ions to 4-amino-2,5-dimethyl pyrimidine (ADMPY) has been compared with the binding of these same metal ions to 2,5-dimethyl-4-hyroxy pyrimidine (HDMPY), analogue of ADMPY in which the amino group has been replaced by a hydroxyl group. A brief comparison is made with the corresponding Pt(II) and Pd(II) complexes of thiamine and oxythiamine. In this paper we report the synthesis, elemental analyses, infrared spectral data, proton and carbon-13 nuclear magnetic resonance studies of these new complexes. A complete assignment of 1H and 13C NMR spectra resonance is presented for both the ligand and the complexes. The results show that the metallation site is the N-1′ position of the ligand in agreement with earlier works [1–3], however, the chemical shifts observed for this ligand upon complexation are larger than the corresponding chemical shifts observed for the 4-amino-2,5-dimethyl pyrimidine analogue contrary to the thiamine/oxythiamine system.

Complexes of platinum(II) and palladium(II) with N-(2-methyl-4-aminopyrimidinyl-5)methylaniline

The reactions of K 2MX 4, where M = Pt(II), Pd(II) and X = Cl, with thiamine derivative, L, N-(2-methyl- 4-aminopyrimidinyl-5)methylaniline have been studied in aqueous medium (1:2 molar ratio). The products of the general formula MLX 2 have been isolated and characterized by elemental analyses, infrared, proton and carbon-13 nuclear magnetic resonance spectra. A complete assignment of 1H and 13C NMR spectra resonances for both the free ligand and its metal complexes is presented for the first time. The results show that this ligand behaves like a bidentate ligand, coordinating through either the exocyclic amino group and the side chain nitrogen donor atom or the endocyclic nitrogens, N-1′ and N′-3′.

Swinholide‐A, a new marine macrolide. Complete assignment of 1H and 13C spectra by 2D NMR techniques

Abstract1H and 13C NMR spectra of the novel marine macrolide swinholide‐A, which provide the basis for its structure elucidation, have been completely assigned by parallel use of 1D and homo‐ and hetero‐nuclear 2D NMR techniques. Swinholide‐A (1) probably a polyketide, is a 22‐membered macrolide embodying a dihydropyran ring and a 10‐carbon side‐chain ending with a substituted tetrahydropyran ring. The high degree of overlap of eleven CH—O and nine CH2 signals in the 1D proton NMR spectrum of 1 necessitated the structure elucidation of swinholide‐A tetraformate (2) by 2D homo‐ (up to 6J with formyl groups) and hetero‐nuclear NMR correlations. Formyl groups can be good structural probes in complex polyalcohols, as shown by the observed 5J and 6J formate couplings in 2.

Hydrogen-bonded 2-hydroxybenzalazines: Complete assignment of1H and13C NMR spectra

The 80 MHz 1H NMR and 20 MHz 13C NMR spectra of eleven substited benzalazines (subsituenst: α-methyl, α,α′-dimethyl, 2-hydroxy, 2,2′-dihydroxy, 4-n-octyloxy, 4,4′-di-n-octyloxy) possessing mesogenic acivity have been assigned using a variety of one-dimensional techniques. These include homonuclear NOE measurements, selective heteronuclear 13C{1H} NOE difference spectroscopy, singlefrequency off-resonance decoupling, spin—echo multiplicity sorting (SEFT) and long-range heteronuclear coupling constant determintion via both gated decoupling and selective excitation (DANTE).

Assignment of 1H and 13C NMR spectra by a combination of homo- and heteronuclear shift correlated two-dimensional NMR. Application to oligosaccharides related to arabinoxylane

It is shown that a combination of homo- and heteronuclear shift correlated 2 D NMR yields correct and complete assignment of 1H and 13C NMR spectra. The amount of the work necessary can be considerably reduced if some of the lines can be unambiguously assigned on the basis of other information or if suitable model compounds are available.The pattern of homonuclear cross-peaks is characteristic for molecular fragments and can be used with advantage to trace out the lines in the spectral regions with heavy overlap. The exactly assigned 13C chemical shifts of disaccharide and trisaccharide related to arabinoxylan agree satisfactorily with the shifts predicted according to the shifts found in the spectra of model mono- and disaccharides measured under the same conditions.