bluuebunny/crossref_metadata_2025_split huggingface dataset:
Die Synthese und der thermische Zerfall des 1,2‐Diazabenzo[e]‐semibullvalens und dessen Beziehung zur Thermolyse des Benzobenzvalens
Authors: Burger Ulrich , Mentha Yves , Jean Thorel Pierre 
Published: December 2004

The Synthesis and the Thermal Decay of 1,2‐Diazabenzo[e]semibullvalene and its Relation to the Thermolysis of BenzobenzvaleneThe [4 + 2]‐photoadduct of naphthalene and 4‐phenyl‐4H‐1,2,4‐triazol‐3,5‐dione (PTAD) was subjected to a triplet‐sensitized di‐π‐methane rearrangement. Hydrolysis of the resulting urazol 15 gave a stable semicarbazide 16 which by nickel‐peroxide oxidation gave 1,2‐diazabenzo[e]semibullvalene (10). At 40 °C, the latter decays in CHCl3 solution to produce benzofulvene (2) as the principal product, accompanied by benzobenzvalene (1) and small amounts of naphthalene. This decay reaction is rationalized in terms of a 1,3‐dipolar cycloreversion which is followed by denitrogenation to give indenyl carbene (19). The thermolysis of 1 in solution is believed to proceed via the same carbene. At present, these findings provide only a partial answer to the benzobenzvalene enigma (i.e., in solution at 150°, 1 gives 2, but in the gas‐phase at 300°, 1 yields naphthalene). MeOH is shown to add readily to 10 in a homologous Michael addition.
Approaches to 1H‐Cyclopropa[l]phenanthrenes. Eliminations with 1a,9b‐Dihydro‐1H‐cyclopropa[l]phenanthrene Derivatives
Authors: Müller Paul , Thi Huong Can Nguyen , Pfyffer Jean 
Published: December 2004

AbstractBase‐induced elimination of the sulfonium salt2iin the presence of furan affords the addition products7and8, derived from 1H‐cyclopropa[l]phenanthrene (1) and the isomeric cyclopropene5a(Scheme 3). Upon oxidation, the selenide2cyields phenanthrene‐9‐methanol (9), presumablyvia1. No evidence for the intermediate1is obtained from sulfoxide pyrolysis with2e, which leads to products formed by radical pathways(Scheme 5). Reductive elimination of the disulfone3bgives half‐reduction to monosulfone2gand complete reduction to cyclopropane2as well as 9‐methylphenanthrene (15), but no evidence for the intermediate1.
Intramolecular Oxygen Transfer on the Ozonolysis of a Diphenylcyclopentene Derivative
Authors: Jefford Charles W. , Boukouvalas John , Jaggi Danielle , Kohmoto Shigeo , Bernardinelli GéRald 
Published: December 2004

AbstractThe ozonolysis of cis‐3,4a,7,7a‐tetrahydro‐3,3‐dimethyl‐6,7a‐diphenylcyclopenta[1,2,4]trioxine (1) in CH2Cl2 at −78° gave the secondary endo ozonide 2 (43% yield) and an acetal 3 (27% yield) derived from O‐insertion at the ortho position of the C(7a) phenyl substituent. Both structures were elucidated by X‐ray. Repetition of the ozonolysis in MeOH/CH2Cl220:3 at −78° also gave the same two products in 12 and 15% yields, repectively, together with the hemiperacetal 4 (54% yield) formally derived from the secondary ozonide by addition of MeOH.
(+)‐(5R,6S)‐2‐(1′‐Aminoalkyl)‐6‐(hydroxyalkyl)penem‐3‐carboxylic Acids
Authors: Lang Marc , Hungerbühler Ernst , Schneider Peter , Scartazzini Riccardo , Tosch Werner , Konopka Edward A. , Zak Oto 
Published: December 2004

AbstractIn continuation of our work on penem antibiotics, novel chiral (5R,6S)‐2‐(1′‐aminoalkyl)‐6‐(hydroxyalkyl)‐derivatives1have been synthesized by two essentially different strategies. Whereas the starting materials for1a‐f, azetidinones2and5, were obtained from chiral building blocks (6‐aminopenicillanic acid and L‐threonine, resp.), the one for1g, azetidinone9, was derived from racemic 4‐acetoxyazetidinone and, as chiral auxiliary, (2R)‐2‐mercaptopropan‐1‐ol. The 2‐aminomethyl derivatives1a(CGP 30 779) and1f(CGP 31 608) proved the most potent compounds in the antibacterial testsin vitroand showed a well‐balanced spectrum of activity by comparison with that of established β‐lactams.
Membrane Structure of Substance P. I. Prediction of Preferred Conformation, Orientation, and Accumulation of Substance P on Lipid Membranes
Authors: Schwyzer Robert , Erne Daniel , Rolka Krzysztof 
Published: December 2004

AbstractPreferred conformation, orientation, and accumulation of substance P on a neutral hydrophilic‐hydrophobic interface was estimated and extrapolated to interactions with neutral and anionic lipid bilayer membranes according to our general procedure. Nine residues at the C‐terminus were predicted to be transferred to the hydrophobic phase as an α‐helical domain, oriented quite perpendicularly on the membrane surface. The N‐terminal residues remained in the aqueous phase with their charges exposed to H2O. The molecular amphiphilic moment vector was strong (338 arbitrary units) and pointed its hydrophilic end towards the N‐terminus, only 15° away from the helix axis. The molecular electric dipole moment vector was also strong (124 debye) and pointed its positive end towards the N‐terminus, only 9° away from the helix axis. Thus, it reinforced the effect of the amphiphilic moment of a peptide intruding into the membrane dipole layer. The estimated dissociation constant for the equilibrium between membrane‐bound and free substance P was Kd ≈︁ 46 mM for neutral membranes, and Kd ≈︁0.43 mM for anionic membranes with a Gouy‐Chapman surface potential of −40 mV. Thus, substance P behaved similarly to dynorphin A and adrenocorticotropin peptides which insert their N‐terminal message segments as perpendicularly oriented helical domains into membranes, whereas their C‐terminal address segments remain in the aqueous phase as random coils. Substance P is the first instance of a neuropeptide which is expected to insert a C‐terminal message into lipid membranes.
Membrane Structure of Substance P. II. Secondary Structure of Substance P, [9‐Leucine]substance P, and Shorter Segments in 2,2,2‐Trifluoroethanol, Methanol, and on Liposomes Studied by Circular Dichroism
Authors: Rolka Krzysztof , Erne Daniel , Schwyzer Robert 
Published: December 2004

AbstractComparative CD studies with substance P (1), [Leu9]substance P ([Leu9]‐1), and their shorter peptide segments supported the membrane structures predicted for substance P and [Leu9]substance P. They indicated that the C‐terminal segments (from residue 3 or 4 onward) can adopt α‐helical conformations in hydrophobic environments and on lipid membranes. The N‐terminal segment, (residues 1–4) had a poly(proline)‐like conformation in aqueous and hydrophobic surroundings. Residues 3 and 4 (Lys‐Pro) appeared to belong to both domains and bring about the transition between the two. The estimated free energies of transfer for 1 and [Leu9]‐1 from their random conformations in H2O to their partially helical conformations on an aqueous‐hydrophobic interface are too small to allow detectable interaction with neutral lipid membranes at low concentrations. The two peptides should, however, interact detectably with anionic membranes because of favourable Boltzmann distribution factors. This prediction was shown to be correct for liposomes prepared from 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (neutral) and phosphatidylserine (anionic).
IR Laser Chemistry and CF Chromophore Absorption of 1,2‐Dichloro‐1,1,2‐trifluoroethane
Authors: Lupo Donald W. , Quack Martin , Vogelsanger Beat 
Published: December 2004

AbstractThe photochemical‐reaction yields after IR multiphoton excitation of CHFCl‐CF2Cl are reported and evaluated in terms of the steady‐state rate coefficient for reactant decay

The dominant primary reaction channels are α,β HCl and HF elimination, although minor pathways seem to include Cl2 elimination and other channels, which are discussed. The major uncertainty in the comparison with theoretical estimates resides in the fraction of CF chromophore band strength which contributes to excitation. The total band strength for the range from 940 cm−1 to 1310 cm−1 is reported to be G = ∫σ(ṽ) (dṽ/ṽ) = 8.2 pm2.
A Short Synthesis of (±)‐(cis‐6‐Methyltetrahydropyran‐2‐yl)Acetic Acid, a Constituent of Civet
Authors: Nussbaumer Cornelius , Fráter Georg 
Published: December 2004

AbstractThe title compound has been synthesized in four steps from (±)‐4‐penten‐2‐ol via a novel β‐alkenyloxyacrylate cyclization reaction 3→6 as the key step (overall yield 35%).
Steric Effects on Reaction Rates. Part IX. Force‐Field Parameters for Bridgehead and Rigid Tertiary Carbenium Ions
Authors: Müller Paul , Mareda Jiri 
Published: December 2004

AbstractMolecular‐mechanics calculations for strain of carbenium ions are tested using Bentley's unified reactivity scale for bridgehead solvolysis as reference. Excellent correlations are obtained for solvolytic bridgehead reactivity with the calculated steric‐energy difference (ΔEst) between substrate (RH or ROH) and cation (R+). After adjustment of appropriate force‐field parameters, the approach is successfully extended to the rigid, but planar cations derived from structures 15–20; however, the general set of parameters cannot be applied to highly strained systems such as the cation formed from 17. With all of the 18 sets of parameters tested, the 2‐endo‐norbornyl derivative 16, is adequately correlated, while the exo isomer 15 exhibits enhanced reactivity by a factor of ca. 102 to 103.
Synthese makrocyclischer, α,β‐ungesättigter γ‐Oxolactone durch Ringerweiterungsreaktionen; ein neuer Weg zum makrocyclischen Lacton‐Antibiotikum A 26771 B
Authors: Bienz Stefan , Hesse Mauhad 
Published: December 2004

Synthesis of Macrocyclic α,β‐Unsaturated γ‐Oxolactones by Ring‐Enlargement Reactions; a New Path to the Macrocyclic Lactone Antibiotic A 26771 BA new synthetic route to the α,β‐unsaturated γ‐oxolactones 2a and 2b, involving two ring‐enlarement reactions, is described. Ring opening of bicyclic α‐nitroketones of the type 3 gave ring‐enlarged compounds of the type 4 which were converted to monoprotected diketones of the type 10 by using a variation of the Nef reaction as a key step. Macrocyclic lactones of the type 11 were obtained by Baeyer‐Villiger oxidation and converted into compounds of the type 2. The conversion of 2b to the macrocyclic lactone antibiotic A 26771 B (1) is already described in the literature.
Synthese Eines Optisch Aktiven Penem‐Zwischenprodukts Mittels Asymmetrischer Amidoalkylierung
Authors: Allmendinger Thomas , Rihs Grety , Wetter Hansjürg 
Published: December 2004

Synthesis of an Optically Active Penem Intermediate by Asymmetric AmidoalkylationThe amidoalkylation of an optically active, cationic glycine derivative with methyl acetoacetate furnishes an intermediate 10a (Scheme 2) that is transformed in six steps to the optically active, silyl‐protected 4‐acetoxy‐3‐(1‐hydroxyenthyl)‐2‐azetidinon 18a, a well known intermediate in penem synthesis.
Dediazoniations of arenediazonium ions part 25 Influence of Substituents on the Exchange of the Diazonio Group for External Molecular Nitrogen and on the N(α), N(β)‐Rearrangement in the Diazonio Group
Authors: Ravenscroft Michael D. , Zollinger Heinrich 
Published: December 2004

AbstractThe N(α), N(β)‐rearrangement of the two N‐atoms which can be observed in solutions of [β‐15N]‐labelled p‐substituted benzenediazonium ions follows dual substituent parameter treatments. The reaction yields a negative field and a positive resonance reaction constant (pF =−3.35, pR = 2.47). The magnitude of these constants is, within experimental error, the same as the respective reaction constants for solvolytic dediazoniation. The exchange of the diazonio group of 15N‐labelled p‐substituted benzenediazonium ion yields, however, field and resonance reaction constants which are close to zero. This result is attributed to cancellation of the reaction constants for the forward and reverse steps in the complex mechanism of the exchange reaction.
Metal Complexes with Macrocyclic Ligands. Part XXVIII.. Structures and stabilities of the Cu2+ complexes with 1,4,7‐triazacyclononane‐1‐acetic acid
Authors: Studer Martin , Riesen Andreas , Kaden Thomas A. 
Published: December 2004

AbstractThe potentiometric study of the complexation of 1,4,7‐triazacyclononane‐l‐acetic acid (1) with Cu2+ (I = 0.5 (KNO3), T = 25°) indicates the presence of the species [Cu(1)], [Cu(1)OH], [Cu(1)2], and [(Cu(1))2OH], the stability constants of which are determined. The two complexes [Cu(1)]ClO4 and [(Cu(1)2)OH]ClO4 were also characterized by X‐ray structure analysis. In both cases, the Cu2+ ion is in a distorted square‐pyramidal arrangement, penta‐coordinated by the three N‐atoms of the macrocycle, an O‐atom of the carboxylate, and an additional O‐atom either from a second carboxylate or from an OH−, acting as a bridge between two metal centres.
Asymmetric Induction on Copper(I) Chloride catalyzed 1,4‐addition of alkylmagnesium chlorides to α, β‐disubstituted (E)‐enoylsultams and subsequent protonation
Authors: Oppolzer Wolfgang , Kingma Arend J. 
Published: December 2004

AbstractSuccessive treatment of conjugated N‐enoylsultams 2 with alkyl Grignard reagents/CuCl and aq. NH4Cl solution generated selectively two stereogenic centers at C(α) and C(β) providing, after flash chromatography and crystallization, acylsultams 5 in high purity. Mild cleavage afforded the recovered sultam auxiliary 1 and enantiomerically pure carboxylic acids 7.
Synthesis of cycloproparenes via aromatization of 7‐Oxanorbornenes with Low‐Valent titanium
Authors: Müller Paul , Schaller Jean‐Pierre 
Published: December 2004

Abstract1H‐Cyclopropa[b]naphthalene 3c and the 2,7‐diphenyl‐substituted derivative 3a have been synthesized via cycloaddition of the appropriate isobenzofurans 1a and 1b to 1‐bromo‐2‐chlorocyclopropene and aromatization of the adducts with low‐valent Ti. The same procedure afforded the 2,7‐dimethyl‐H‐cyelopropa[g]isoquinoline (15), but failed for the parent azacompound. Reaction of adducts of furans to 1‐bromo‐2‐chlorocyclopropenes with low‐valent Ti produced mixtures of cyclopropabenzenes 19 and 1,6‐dihalogeno‐1,3,5‐cycloheptatrienes 18. The latter could be converted to cyclopropabenzenes with BuLi.
Thermal Valence Rearrangements of Heterocycles. Part 2. A new synthetic approach towards the indole ring system
Authors: Bennett Grace A. , Mullen George B. , Georgiev Vassil St. 
Published: December 2004

AbstractA new synthetic approach towards the indole ring system is described. When dimethyl 1‐methyl‐2‐oxa‐1‐aza‐spiro[4.5]dec‐3‐ene‐3,4‐dicarboxylate (6) was refluxed in toluene, the previously known dimethyl 4,5,6,7‐tetra‐hydro‐1‐methyl‐1H‐indole‐2,3‐dicarboxylate (7) was obtained in 71% yield, via a 2,3‐dihydroisoxazole‐pyrrole rearrangement. After treatment with DDQ, the tetrahydro analogue 7 was converted to the corresponding dimethyl 1‐methyl‐1H‐indole‐2,3‐dicarboxylate (8).
Technical Procedures for the Syntheses of Carotenoids and Related Compounds from 6‐Oxo‐isophorone: Syntheses of (3R,3′R)‐Zeaxanthin. Part I
Authors: Widmer Erich , Soukup Milan , Zell Reinhard , Broger Emil , Wagner Hans Peter , Imfeld Marquard 
Published: December 2004

AbstractStarting from the readily available, optically active (4R)‐4‐hydroxy‐2,2,6‐trimethylcyclohexanone (1), a new technical synthesis of (3R,3′R)‐zeaxanthin is described. According to a 2(C9 + C6) + C10 = C40 construction scheme, the ketone 1 was first transformed with (E)‐3‐methylpent‐2‐en‐4‐yn‐1‐ol (5) into a C15‐intermediate which, by a three‐step sequence, could be converted into the known olefinic C15‐Wittig salt 4. Optimized conditions for the final Wittig reaction of 4 with the C10‐dialdehyde 3 are discussed. Based on 1, the overall yield of the entire technical process is ca. 40%.
Reduction of Indolin‐2‐ones and Desulfurization of Indoline‐2‐thiones to Indoline and Indole Derivatives
Authors: Nishio Takehiko , Okuda Norikazu , Kashima Choji 
Published: December 2004

AbstractReduction of indolin‐2‐ones with lithium aluminium hydride (LAH) or diisobutylaluminum hydride (DIBAL) and desulfurization of indoline‐2‐thiones with Raney‐Ni were investigated. Treatment of indoline‐2‐ones 1 with LAH or DIBAL yield indoles 4 and/or indolines 3 in moderate‐to high yield depending on the substituents at N and C(3) of 1. Indoline‐2‐thiones 2 were desulfurized with Raney‐Ni to give indoles 4 and/or indolines 3.
Relative Configuration and Conformation of 5‐(Dimethoxyphosphoryl)‐2‐methoxy‐1,2λ5‐oxaphospholan‐2‐ones by Multinuclear NMR Spectroscopy
Authors: Kalchhauser Hermann , Öhler Elisabeth 
Published: December 2004

AbstractInformation on the hitherto unknown relative configuration and on the conformation of the title compounds in solution can be derived from nuclearOverhausereffects and coupling constants. Whereas the bridged 5‐(dimethoxyphosphoryl)‐2‐methoxy‐1,2λ5‐oxaphospholan‐2‐ones6and7are sterically strained and, therefore, conformationally rigid, the C(3)‐unsubstituted compound1does not show a preferred solution conformation. Phenyl substituents at C(3) (compounds2–5) tend to adopt a pseudoequatorial position, this way leading to a definite conformation of the respective compounds. The influence of the conformation on the NMR spectra is discussed.31P‐NMR Spectroscopy is ideally suited for the characterization and quantification of the isomers2–5present in the reaction mixture.
Rogiolenyne D, the likely immediate precursor of rogiolenyne A and B, branched C15 acetogenins isolated from the red seaweed Laurencia microcladia of II Rogiolo. Conformation and absolute configuration in the whole series
Authors: Guella Graziano , Mancini Ines , Chiasera Giuseppe , Pietra Francesco 
Published: December 2004

AbstractIt is shown that in the red seaweed Jaurencia microcladia, collected in the Mediterranean off the torrent Il Rogiolo, the new branched C15 acetogenin rogiolenyne D ( = (+)‐(2S,3S,7R))‐3‐(bromomethyl)‐7‐[(Z)‐1‐chlorohexen‐3‐en‐5‐nyyl)]‐2‐ethyl‐2,3,6,7‐tetrahydrooxepin; (+)‐−3 co‐occurs with the already reported rogiolenyne A ((−)‐1) and B ((−)‐2a, suggesting the lineage (+)‐3→(−)‐1(−)‐2a,Which is realized here chemically. The relative configurations are established via NMR analysis and chemical transformations as regards the seven‐membered ring, while recourse is made to conformational analysis for the side chain. The absolute configuration is established via the Mosher's NMR method applied to the MPTA esters of (−)‐2a.
Glycosylidene Carbenes. Part 6. Synthesis of alkyl and fluoroalkyl glycosides
Authors: Briner Karin , Vasella Andrea 
Published: December 2004

AbstractThe syntheses of glycosides from the diazirine 1 and a range of alcohols under thermal and/or photolytic conditions are described. Yields and diastereoselectivities depend upon the pKHA values of the alcohols, the solvent, and the reaction temperature. The glycosidation of weakly acidic alcohols (MeOH, EtOH, i‐PrOH, and t‐BuOH, 1 equiv. each) in CH2Cl2 at room temperature leads to the glycosides 2–5 in yields between 60 and 34% (Scheme 1 and Table 1). At −70 to −60°, yields are markedly higher. In CH2Cl2, diastereoselectivities are very low. In THF, at −70 to −60°, however, glycosidation of i‐PrOH leads to α‐D‐/β‐D‐4 in a ratio of 8:92. More strongly acidic alcohols, such as CF3CH2OH, (CF3)2 CHOH, and (CF3)2C(Me)OH, and the highly fluorinated long‐chain alcohols CF3(CF2)5(CH2)2OH (11) and CHF2(CF2)9CH2OH (13) react (CH2Cl2, r.t.) in yields between 73 and 85% and lead mainly to the β‐D‐glucosides β‐D‐6 to β‐D‐8, β‐D‐12, and β‐D‐14 (d.e. 14–68%). Yields and diastereoselectivities are markedly improved, when toluene, dioxane, 1,2‐dimetoxyethane, or THF are used, as examined for the glycosidation of (CF3)2C(Me)OH, yielding (1,2‐dimethoxyethane, 25°) 80% of α‐D‐/ β‐D‐8 in a ratio of 2:98 (d.e. 96%; Table 4). In EtCN, (CF3)2C(Me)OH yields up to 55% of the imidate 10. Glycosidation of di‐O‐isopropylideneglucose 15 leads to 16 (CH2Cl2, r.t.; 65%, α‐D/ β‐D = 33:67). That glycosidation occurs by initial protonation of the intermediate glycosylidene carbene is evidenced, for strongly acidic alcohols, by the formation of 10, derived from the attack of (CF3)2MeCO− on an intermediate nitrilium ion (Scheme 4), and for weakly acidic alcohols, by the formation of α‐D‐9 and β‐D‐9, derived by attack of i‐PrO− on intermediate tetrahydrofuranylium ions. A working hypothesis is presented (Scheme 3). The diastereoselectivities are rationalized on the basis of a protonation in the σ plane of the intermediate carbene, the stabilization of the thereby generated ion pair by interaction with the BnOC(2) group, with the solvent, and/or with the alcohol, and the final nucleophilic attack by RO− in the π plane of the (solvated) oxonium ion.
An Alternative Access to (±)‐α‐Irones and (±)‐β‐Irone via Acid‐Mediated Cyclisation
Authors: Schulte‐Elte Karl H. , Pamingle Hervé , Uijttewaal Arnold P. , Snowden Roger L. 
Published: December 2004

AbstractAcid‐mediated cyclisation of trienone 8, readily available from 2,3‐dimethylbutanal (1; five steps: 47% yield), using fluorosulfonic acid (6.8 mol‐equiv.) in 2‐nitropropane at −70°, afforded a 14:9:1 mixture (70% yield) of (±)‐cis‐α‐irone (9), (±)‐trans‐α‐irone (10), and (±)‐β‐irone (11). Other acidic conditions examined, using 95% aq. H2SO4 solution, 85% aq. H3PO4 solution, or SnCl4, gave inferior results.
Structural and Photophysical Properties of Lanthanide Nitrate 1:1 Complexes with planar tridentate nitrogen ligands analogous to 2,2′:6′,2′‐terpyridine
Authors: Piguet Claude , Williams Alan F. , Bernardinelli Gérald , Moret Emmanuel , Bünzli Jean‐Claude G. 
Published: December 2004

AbstractThe ligand 2,6‐bis(1‐methylbenzimidazol‐2‐yl)pyridine (mbzimpy, 1) reacts with EuIII to give [Eu(mbzimpy)(NO3)3(CH3OH)] [4] whose crystal structure (EuC22H21N8O10, a = 7.658(3) Å, b = 19.136(2) Å, c = 8.882 Å, β = 104.07(1)°, monoclinic, P21, Z = 2) shows a mononuclear structure where EuIII is ten‐coordinate by a meridional tridentate mbzimpy ligand, three bidentate nitrates, and one CH3OH molecule, leading to a low‐symmetry coordination sphere around the metalion. Essentially the same coordination is found in the crystal structure of [Eu(obzimpy)(NO3)3] (8) (EuC35H45N8O9, a = 9.095(2) Å, b = 16.624(2) Å, c = 26.198(6) Å, β = 95.85(1)°, monoclinic, P21/c, Z = 4) obtained by reaction of 2,6‐bis(1‐octylbenzimidazol‐2‐yl)pyridine (obzimpy, 2) with EuIII. Detailed photophysical studies of crystalline [Ln(mbzimpy)(NO3)3(CH3OH)] and [Ln(obzimpy)(NO3)3] complexes (Ln = Eu, Gd, Tb, Lu) show that 1 and 2 display 1ππ* and 3ππ* excited states very similar to those observed in 2,2′:6′,2″‐terpyridine, leading to efficient ligand to LnIII intramolecular energy transfer. Spectroscopic results show that an extremely efficient mbzimpy‐to‐EuIII transfer occurs in [Ln(mbzimpy)(NO3)3(CH3OH)] and in the case of TbIII, a TbIII‐to‐mbzimpy back transfer is also implied in the deactivation process. The origin of these peculiar effects and the influence of ligand design by going from mbzimpy to obzimpy are discussed. 1H‐NMR and luminescence data indicate that the structure found in the crystal is essentially maintained in solution.
Peptide Conformation from Coupling Constants: Scalar Couplings as Restraints in MD Simulations
Authors: Eberstadt Matthias , Mierke Dale F. , Köck Matthias , Kessler Horst 
Published: December 2004

AbstractThe question of how far one can go in the determination of conformation with the sole use of coupling constants as restraints in MD simulations was addressed. Couplings are being used ever more frequently as constraints as measuring heteronuclear long‐range coupling constants becomes easier. For this investigation, cyclosporin A, which has previously been extensively examined with NOE‐restrained simulations, is used as a model system. Many additional one‐and three‐bond coupling constants have been measured. The MD simulations were carried out with the addition of a potential‐energy penalty function based directly on the Karplus curve. It is shown that, for dihedral angles with more than one coupling, the restraints are very efficient, in agreement with the structure observed from NOEs. However, it turned out that the structure of CsA is not adequately described, when only J couplings are used.