13C-labeled platinum(IV)-carbohydrate complexes: structure determination based on (1)H-(1)H, (13)C-(1)H, and (13)C-(13)C spin-spin coupling constants

The reaction of D-mannose and D-allose with [PtMe(3)(Me(2)CO)(3)]BF(4) 1 in acetone affords complexes [PtMe(3)L]BF(4) 5 and 6 (5, L = alpha-D-mannofuranose; 6, L = beta-D-allofuranose). The coordination mode and conformation of the carbohydrate ligands in 5 and 6 in acetone-d(6) have been determined from an analysis of J(HH), J(CH), and J(CC) in complexes formed using site-specific (13)C-labeled D-mannose and D-allose. These coupling data are compared to those measured in (13)C-labeled complex [PtMe(3)L]BF(4) 2 (L = 1, 2-O-isopropylidene-alpha-D-glucofuranose) and 1, 2-O-isopropylidene-alpha-D-glucofuranose 3, whose solid-state structures are known, and in (13)C-labeled 1,2;5, 6-di-O-isopropylidene-alpha-D-glucofuranose 4. The preferred furanose ring conformations in 2 and 5 are very similar ((3)E/E(4) and E(4)/(o)E/E(1), respectively; eastern hemisphere of the pseudorotational itinerary), with platinum coordination involving O3, O5, and O6 of the saccharide. In contrast, the furanose ring of 6 prefers an (4)E/E(o)/(1)E geometry (western hemisphere of the pseudorotational itinerary) resulting from altered complexation involving O1, O5, and O6. Couplings within the exocyclic fragments of 2, 5, and 6 also support the existence of two different platinum coordination modes. In addition to establishing the structures and conformations of 2, 5, and 6 in solution, one-, two-, and three-bond J(CH) and J(CC) observed in these complexes provide new insights into the effect of structure and conformation on the magnitudes of these couplings in saccharides. Weak platinum(IV) complexation with the carbohydrate conformationally restricts the furanose and exocyclic fragment without introducing undesirable structural strain, thereby allowing more reliable correlations between structure and coupling magnitude.     

A Convenient Synthesis of (1 1E, 13E)-11, 13-Hexadecadienal and (11Z, 13E)-Hexadecadienal

A simple method for synthesizing (11E, 13E)-11, 13-hexadecadienal 7, a component of the female sex pheromone of cabbage webworm, and its geometrical isomer (11Z, 13E)-11, 13-hexadecadienal 8 is described.     

(13)C-(1)H and (13)C-(13)C NMR J-couplings in (13)C-labeled N-acetyl-neuraminic acid: correlations with molecular structure

N-acetyl-neuraminic acid (Neu5Ac, 2) was prepared enzymatically containing single sites of (13)C-enrichment at C1, C2, and C3. Aqueous solutions of the three (13)C isotopomers were studied by (1)H and (13)C NMR spectroscopy at p(2)H 2 and pH 8 to obtain J(CH) and J(CC) values involving the labeled carbons. Experimental studies were complemented by DFT calculations of the same set of J-couplings in protonated and ionized structural mimics of 2 to determine how well theoretical predictions match the experimental findings in saccharides bearing ionizable functionality. Results show that: (a) (2)J(C2,H3ax/eq) values in 2 depend on anomeric configuration, thus complementing (3)J(C1,H3ax/eq) behavior, (b) J(CH) and J(CC) values involving C2 depend on anomeric configuration, the C1-C2 bond torsion, and solution pH, and (c) long-range (4)J(C2,H7) is sensitive to glycerol side-chain conformation. Intraring J(HH) and most (2)J(CH), (3)J(CH), (2)J(CC), and (3)J(CC) involving C1-C3 of 2 appear largely unaffected by the ionization state of the carboxyl group. In vacuo and solvated DFT calculations of geminal and vicinal J(CH) and J(CC) values are similar and reproduce the experimental data well, but better agreement with experiment was observed for (1)J(C1,C2) in the solvated calculations. The present work provides new information for future treatments of trans-glycoside couplings involving Neu5Ac residues by (a) providing new standard values of intraring J(CC) for coupling pathways that mimic those for trans-glycoside J(CC), (b) identifying potential effects of solution pH on trans-glycoside couplings inferred through the behavior of related intraring couplings, and (c) providing specific guidelines for more reliable DFT predictions of J(CH) and J(CC) values in ionizable saccharides.     

Order parameters based on (13)C(1)H, (13)C(1)H(2) and (13)C(1)H(3) heteronuclear dipolar powder patterns: a comparison of MAS-based solid-state NMR sequences

Order parameters describing conformational exchange processes on the nanosecond to microsecond timescale can be obtained from powder patterns in solid-state NMR (SSNMR) experiments. Extensions of these experiments to magic-angle spinning (MAS) based high-resolution experiments have been demonstrated, which show a great promise for site-specific probes of biopolymers. In this study, we present a detailed comparison of two pulse sequences, transverse Manfield-Rhim-Elleman-Vaughn (T-MREV) and Lee-Goldburg cross-polarization (LGCP), using experimental and simulation tools to explore their utility in the study of order parameters. We discuss systematic errors due to passively coupled (13)C or (1)H nuclei, as well as due to B(1) inhomogeneity. Both pulse sequences can provide quantitative measurements of the order parameter, but the LGCP experiment is capable of greater accuracy provided that the B(1) field is highly homogeneous. The T-MREV experiment is far better compensated for B(1) inhomogeneity, and it also performs better in situations with limited signal.     

First principles study of the stability and electronic structure of the icosahedral La13, La(-1) (13), and La(+1) (13) clusters

The structural stability and electronic-structure of icosahedral La(13), La(-1) (13), and La(+1) (13) clusters have been studied by DMOL cluster method based on density-functional theory. The ground state of all-electron with relativity results is shown to be a distorted D(2h) icosahedron by the Jahn-Teller effect. However, the binding energies of D(3d) and D(5d) are very close to that of the D(2h) structure for La(13), La(-1) (13), and La(+1) (13) clusters. The effective core potential results show that the true ground state is D(5d) structure. The clusters have small magnetic moments and the symmetry of cluster is an important factor in determining the magnetic moments of the clusters. The effects of interatomic spacing and coordination on atomic magnetic moment are discussed. Further, 5d electrons dominate the hybrid orbitals below the Fermi level in the neutral cluster and contribute the main spin of clusters.     

Synthesis of 12(R),13(S)-oxido-9z-octadecenoic (vernolic) and 13(S)-hydroxy-9z, 11E-octadecadienoic (coriolic) acids

(-)-Vernolic acid was prepared enantiospecifically from a readily available carbohydrate precursor and Isomerized to (+)-coriolic acid using the methylmagnesium salt of     

Substituenteneffekte auf die NMR-Spektren von Pentafulvenen. (13C, 13C)-NMR-Kopplungskonstanten (1J(C,C))

Substituent Effects on NMR Spectra of Pentafulvenes. ¹³C, ¹³C-NMR Coupling Constants (¹J(C, C)) ¹H- and ¹³C-NMR spectra of 6-monosubstituted pentafulvenes 1 – 8 have been analysed, and ¹J(C, C) coupling constants have been determined from ID-inadequate spectra of ¹³C satellites. It turns out that ¹³C,¹³C coupling constants of the ring C-atoms, and especially J(1,2)/J(3,4) and J(2,3), reflect the extent of π delocalisation in the fulvene ring. With increasing electron-donating capacity of the substituent R, J(1,2)/J(3,4) values are decreasing, while J(2,3) (and J(1,5)/J(4,5) as well) are increasing, and linear correlations of Hammett substituent constants σ⁺ and ¹J(C,C) values are obtained.     

Structure and stability of Al13H(n) (n=1-13) clusters: exceptional stability of Al13H13

We have performed density functional calculations for the structure and stability of Al(13)H(n) (n=1-13) clusters. Population analysis has shown significant charge transfer occurring from the Al cluster to the H atoms. The population for Al(13) varies from 0.24 (Al(13)H) to 2.83 (Al(13)H(13)). The shape of Al(13) moieties in the Al(13)H(n) (n>/=8) clusters is significantly distorted from the icosahedral structure of Al(13) and is a "cagelike" form. Al(13)H(13) has a capped icosahedron as the ground-state structure, similar to B(13)H(13), while the shape of B(13) (planar) is different from Al(13) (icosahedral). The Al(13)H(13) cluster is predicted to be exceptionally stable on the basis of the high stabilization energy and the negative nucleus independent chemical shift value.     

13-Acetoxy-heptadecadien-(8, 10)-ol-(1), Octadien-(3, 5)-ol-(1)-Isomere und verwandte Verbindungen

Zusammenfassung Es werden diecis,cis- undtrans,trans-Isomeren der primären Alkohole Octadien-(3,5)-ol-(1) (I), 15-Acetoxy-nonadeca-dien-(10,12)-ol-(1) (IV), 17-Acetoxy-heneikosa-dien-(10,12)-ol-(1) (V), 12-Acetoxy-pentadeca-dien-(8,10)-ol-(1) (VII) und 13-Acetoxy-heptadeca-dien-(8,10)-ol-(1) (VI) synthetisiert und zusammen mit einigen Zwischenprodukten und Analogen unter Verwendung des Seidenspinners (Bombyx mori L.) und des Schwammspinners (Lymantria dispar L.) auf Attraktivität getestet. DieL. E.-Werte der synthetisierten cis,cis-VI-Präparate liegen in der Größenordnung von 10^–9 g/ml.

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Thecis, cis- andtrans, trans-isomere of the primary alcohols octadien-(3,5)-ol-(1) (I), 15-acetoxy-nonadecadien-(10,12)-ol-(1) (IV), 17-acetoxy-heneicosadien-(10,12)-ol-(1) (V), 12-acetoxypentadecadien-(8,10)-ol-(1) (VI) have been synthesized and tested for effectiveness as attractant together with several intermediates and analogues using the Silk Moth (Bombyx mori L.) and the Gipsy Moth (Lymantria dispar L.) The values of the attractant units of the cis, cis-VI-compounds synthesized are of the order 10^–9 g/ml.

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4. Mitt. der Reihe Synthese und Wirksamkeit von Sexualduftstoff-Analogen; 3. Mitt.:R. Riemschneider, A. Kühnl undK. Brockmeyer, unveröffentlichte Versuche; 2. Mitt.:R. Riemschneider undG. Kasang, Z. Naturforschg.18 b, 646 (1963); 1. Mitt.:R. Riemschneider, Vortrag vom 1. 9. 1962 in S. Paolo.     

Simultaneous and accurate determination of one-bond (15)N-(13)C' and two-bond (1)H(N)--(13)C' dipolar couplings

Using the echo-anti-echo manipulation, the 15N-1HN cross-peaks split in the E.COSY spectrum by the 13CO couplings are separated into different, distinct regions in the HSQC spectrum. From this novel E.COSY 15N-1HN HSQC spectrum, the small one-bond 15N-13C' and two-bond 1HN-13C' residual dipolar couplings can be extracted easily and accurately. These dipolar couplings provide a set of important long-range constraints for protein structure determination.     

STRUCTURE OF 3-(N-METHYL- β-NAPHTHYLAMINO)-ACROLEIN,C_(14)H_(13)NO

<正> M=211.28, monoclinic, P21/c, a=10.268(2), b=11.581(2), c=9.605(2)A, β=100.40(2)°, V=1123.5(4)A3, 2=4, Dx=1.25 g/cm3, λ=0.71069A, u=0.73 cm-1, F(000)=448, room temperature, R=0.041. The planes of the formylvinyl groupand the naphthyl ring are tilted with respect to the plane of nitrogen frameN by 8.6 and 33.6 , respectively. The O atom and the methyl group are in Z position.     

13th European Symposium on Organic Chemistry (13 ESOC)

Russian Journal of Organic Chemistry -     

Measurement of (13)C(alpha)-(13)C(beta) dipolar couplings in (15)N,(13)C,(2)H-labeled proteins: application to domain orientation in maltose binding protein.

TROSY-based HN(CO)CA 2D and 3D pulse schemes are presented for measurement of (13)C(alpha)-(13)C(beta) dipolar couplings in high molecular weight (15)N,(13)C,(2)H-labeled proteins. In one approach, (13)C(alpha)-(13)C(beta) dipolar couplings are obtained directly from the time modulation of cross-peak intensities in a set of 2D (15)N-(1)HN correlated spectra recorded in both the presence and absence of aligning media. In a second approach 3D data sets are recorded with (13)C(alpha)-(13)C(beta) couplings encoded in a frequency dimension. The utility of the experiments is demonstrated with an application to an (15)N,(13)C,(2)H-labeled sample of the ligand free form of maltose binding protein. A comparison of experimental dipolar couplings with those predicted from the X-ray structure of the apo form of this two-domain protein establishes that the relative orientation of the domains in solution and in the crystal state are very similar. This is in contrast to the situation for maltose binding protein in complex with beta-cyclodextrin where the solution structure can be generated from the crystal state via a 11 degrees domain closure.     

13C,13C coupling constants from a mixture of isotopomers (13C) of substituted aromatic compounds; 1-nitronaphthalenes

¹³C Homonuclear decoupling experiments led to the assignment of the carbon-carbon coupling constants of ¹³C-enriched 1-nitronaphthalene obtained by nitration of [1-¹³C]naphthalene. The effects of substituents on coupling constants can be explained on the basis of the electronegativity of the first atom of the substituent, and the observed substituent effects are shown to be parallel to previous data for oxygen containing substituents.