bluuebunny/crossref_metadata_2025 huggingface dataset:
Organophosphorus Compounds, 119. The Phosphaalkyne Cyclotetramer System — Syntheses, Valence Isomerizations, and Reactions
Authors: Mack Andreas , Regitz Manfred
Published: July 2007

In contrast to their all‐carbon analogues, phosphaalkyne cyclooligomers only became accessible a few years ago. A milestone in the chemistry of cyclotetramers was the synthesis and structural characterization of the tetraphosphacubane 5, obtained as a thermolysis product of tert‐butylphosphaacetylene (1). Since then, the construction of eleven cyclotetramers has been achieved, covering seven different frameworks (A‐G). As a consequence of the use of kinetically stabilized phosphaalkynes as starting materials, all known cyclotetramers bear sterically demanding substituents (tert‐butyl, tert‐pentyl, 1‐adamantyl). Cyclotetramerizations are not only achieved by thermolysis of 1, but also by alternative and selective routes such as transition‐metal‐mediated, Lewis acid‐ and base‐induced processes, as well as by cycloadditions to phosphaalkyne cyclotrimers. Interestingly, these tetramers can be interconverted by various valence isomerizations. The results of thermal and photochemically‐induced rearrangements are in good agreement with MO calculations carried out for the parent compounds. Phosphaalkyne cyclotetramers exhibit a highly interesting reactivity and other peculiar features. One outstanding example is the tetraphosphacubane 5, which shows unusual structural and spectroscopic properties as a result of its unique bonding arrangement.
Organoamido‐ and Aryloxo‐Lanthanoids, 17 Novel Low‐Coordinate Lanthanoid (II) and ‐(III) Aryloxide Complexes ‐ the X‐ray Structures of Bis (2,6‐diphenylphenolato) tris(tetrahydrofuran)‐ytterbium (II), Bis(1,2‐dimethoxyethane)bis(2,6‐diphenylphenolato)ytterbium(II),‐neodymium(III)
Authors: Deacon Glen B. , Feng Tiecheng , Junk Peter C. , Skelton Brain W. , White Allan H.
Published: July 2007

Reduction of [Yb(Odpp)3(THF)2(HOdpp = 2,6‐diphenylphenol; THF = tetrahydrofuran) with ytterbium powder and mercury metal yields [Yb(Odpp)2(THF)3] (1) which on crystallization from DME gives [Yb(Odpp)2(DME)2] (2) (DME = 1,2‐dimethoxyethane). Crystallization of the reactant [Yb(Odpp)3(THF)2] from DME yields [Yb(Odpp)3(DME)]. (DME)0,5 (3) and of [Nd(Odpp)3(THF)2] from DME/THF the analogous [Nd(Odpp)3(DME)]. (THF) (4). The X‐ray crystal structure of 1 reveals distorted trigonal bipyramidal five‐coordinate ytterbium with axial Odpp ligands [O‐Yb‐O 164.6(3)˚], and unsymmetrically distributed equatorial THF ligands [O‐Yb‐O 137.5(3), 138.8(3), 83.7(4)°] owing to two close H(Ph)...Yb approaches (3.1‐3.2 Å). In 2, there is trigonal prismatic six‐coordination with an Odpp ligand on each triangular face and DME ligands bridging the triangular faces. Both 3 and 4 have distorted square planar five‐coordination for the lanthanoid metals with an apical Odpp ligand and cisoid Odpp ligands and a chelating DME in the square plane.
Cp3Zr(acetonitrile)+: Structure of an Electron‐Rich Organometallic d0‐Cation
Authors: Brackemeyer Thomas , Erker Gerhard , Fröhlich Roland , Prigge Jörg , Peuchert Ulrich
Published: July 2007

The organometallic salt [Cp3Zr(N≡C‐CH3)]+[CH3B‐(C6F5)3]−(3a) has been prepared by treatment of Cp3ZrCH3with B(C6F5)3followed by the addition of acetonitrile. X‐ray crystal structure analysis of3ashows that its cation consists of three uniformly coordinated η5‐cyclopentadienyl ligands about the zirconium atom. The acetonitrile ligand is end‐on coordinated. In the linear [Zr] ‐N≡C‐CH3unit the C≡N triple bond [N‐C2 1.126(5) Å] is slightly shorter than in the free acetonitrile molecule [dC≡N= 1.141(2) Å], the structure of which was determined as a reference by X‐ray diffraction of a crystal obtained by IR‐laser‐induced zone melting on the diffractometer.
Contribution to the Chemistry of Boron, 238 Synthesis and Assembly Mechanism for Spirocyclic Cage Compounds Containing, B, P and Si Atoms
Authors: Chen Tuqiang , Duesler Eileen N. , Paine Robert T. , Nöth Heinrich
Published: July 2007

Reactions of 1‐lithio · DME‐2,4‐bis(dialkylamino)‐l,3,2,4‐diphosphadiboretanes (1a, 1b) with SiCl4 followed by dehydrohalogenation with tBuLi produce spirocyclic compounds [(R2NB)2P2]2Si (2a, 2b). The compounds have been characterized by spectroscopic methods and X‐ray crystallography. The assembly process has also been followed and one intermediate species [(iPr2NB)2P2][(iPr2NB)P(H)(iPr2NB)P]SiCl (3) has been isolated and fully characterized.
(η6‐Arene)ruthenium(II) Labeling of Amino Acids and Peptides with Aromatic Side‐Chains
Authors: Wolff Jens M. , Sheldrick William S.
Published: July 2007

Bis(arene)ruthenium(II) complexes of the type [(η6‐cymene)Ru(η6‐aa)](CF3SO3)n (2‐9) containing L‐tyrosine and L‐tryptophan derivatives may be prepared by treatment of [(η6‐cymene)Ru({CH3)2CO}3](CF3SO3)2 with the appropriate bioligand in CH2Cl2, for fully protected compounds and CF3COOH for α‐amino acids (aa) with unprotected amine or carboxylic acid groups. Whereas the tyrosine and tryptophan methyl ester complexes [(η6‐cymene)Ru(η6‐H2tyrOMe)](CF3SO3)3 (4) and [(η6‐cymene)Ru(η6‐H2trpOMe)](CF3‐SO3)3 (8) contain trications with protonated amino functions, the remaining compounds all exhibit dications. The crystal structure analysis of [(η6‐cymene)Ru(η6‐HtyrOH)](CF3SO3)2 (5) confirms a marked distortion towards an η5‐oxohexadienyl coordination with deprotonation of the aromatic side chain. Although facial isomers are formed in an effectively 1:1 ratio for all tryptophan derivatives fractional crystallization allowed an X‐ray structural characterization of the β‐isomer of [(η6‐cymene)Ru(η6‐ActrpOMe)](CF3SO3)2 (6). Chemospecific labeling of the tryptophan side chain was established for the mixed dipeptide phenylalanyltryptophan.
Enantioselective Catalysis, XV Preparative and Structural Chemistry of Diastereomeric Derivatives of 3‐Phosphanylpyrrolidine and Their Palladium(II) Complexes ‐ Asymmetric Grignard Cross‐Coupling Reaction
Authors: Nagel Ulrich , Nedden Hans Günter
Published: July 2007

The preparation of both diastereomeric derivatives of 3‐(diphenylphosphanyl) pyrrolidine with chiral (tetrahydrofuran‐2‐yl)methyl and [(N‐neopentyl)pyrrolidin‐2‐yl]methyl groups as substituents on the pyrrolidine nitrogen atom and of (2S,4S)‐1‐benzyl‐4‐(diphenylphosphanyl)‐2‐(methoxymethyl) pyrrolidine is reported. [3S,P(RS)]‐3‐(phenylphosphanyl) pyrrolidine, bearing an additional chiral center on phosphorus, is the starting material for the preparation of phosphanes, in which one phenyl group of the PPh2moiety is substituted by an 2‐methoxyphenyl (=An) or 2,4,6‐trimethoxyphenyl (=TMP) group. PdI2complexes of these ligands were separated into diastereomers by chromatography on silica gel columns. The structural chemistry of these novel phosphane diastereomers and their PdI2complexes is investigated by X‐ray crystallography and NMR. At theP,N‐coordinated palladium center displacement of an iodide anion is found for P,N,N′ ligands only. In the nickel complex catalysed cross‐coupling reaction, yielding 3‐phenyl‐1‐butene, we obtain the highest enantioselectivities in the case of simple 1‐alkyl‐3‐(diphenylphosphanyl)pyrrolidine ligands. The enantioselectivity obtained with diastereomeric derivatives, bearing additional ether or amine ligating sites is mainly determined by the chiral center in 3‐position of the 3‐(phosphanyl) pyrrolidine part of these ligands. Optimisation of enantioselectivity with these ligands can be carried out by a variation of the ligand to nickel ratio and by the choice of the vinyl halide used as starting compound. The catalytic cycle must contain at least one catalytically active species, bearing more than one β aminoalkylphosphane ligand.
Pseudoelement Compounds, X Synthesis and Crystal Structure of New Complexes of the Type trans‐[Pt(H)X(PPh3)2 with Cyanamide and Cyanomethanide Ligands
Authors: Jäger Lothar , Tretner Carola , Hartung Helmut , Biedermann Mathias
Published: July 2007

The new coordination compounds trans‐[Pt(H)X(PPh3)2] with NCN‐ and C(CN)2‐functionalized anions (X− = [N(O)C(CN)2]−, [NO2NCN]−, [N{C(CN)2}2]−, [NCC{C‐(CN)2}2]−, have been characterized by 1H‐, 31P‐, 13C‐NMR, and IR spectroscopy and elemental analyses the crystal structures of trans‐[Pt(H)N(O)C(CN)2(PPh3)2], trans‐ [Pt(H)N{C(CN)2}2(PPh3)2], and trans‐[Pt(H)NCC{C(CN)2}2‐(PPh3)2) have been determined by X‐ray diffraction. Remarkably, [N(O)C(CN)2]− is coordinated through the central nitrogen atom, while [N{C(CN)2}2]− and [NCC(C(CN)2]2]− are bonded through terminal nitrogen atoms of a C(CN)2 unit.
The Reactivity of Complexes of Nickel(0) and Platinum(0) Containing Benzyne and Related Small‐Ring Alkynes
Authors: Bennett Martin A. , Wenger Eric
Published: July 2007

The preparation and reactivities of cyclohexyne and aryne complexes of platinum(0) and nickel(0) are reviewed. These complexes undergo insertions with unsaturated molecules such as alkenes, alkynes, isocyanides, CO and CO2. In the case of the nickel‐ benzyne complexes, consecutive insertions are observed with alkynes, leading to substituted naphthalenes with good regioselectivities. A possible mechanism for these double insertions, based on a combination of steric and electronic factors, is discussed in detail.
Thio‐Ligation to Vanadium: The NSSN and S′N′O Donor Sets (N = Pyridine, N′ = Enamine; S = Thioether, S′ = Thiolate)
Authors: Farahbakhsh Mahin , Nekola Henning , Schmidt Häke , Rehder Dieter
Published: July 2007

The tetradentate, neutral disulfide [bis(thioether)] ligand 1,6‐bis(o‐pyridyl)‐2,4‐dithiahexane, NSSN, reacts with [VCI2(tmeda)2] to form the octahedral (all‐cis; C2v‐symmetric) complex [VCl2(NSSN)] 1, the first low‐valent vanadium complex in which the thio functions are exclusively organic sulfides. Treatment of (VOCl2(thf)2] with O‐mercaptoaniline, followed by reaction with o‐hydroxynaphthaldehyde yields the non‐oxo V′” complex [V(S′N′O)2] 2, derived from the Schiff base HS′N′OH, where 0 and S′ are phenolate and thiophenolate functions, respectively, and N′ is the Schiff base (enamine) nitrogen. Complex 2, with the ligands in a distorted trigonal‐antiprismatic array, is a rare example of a structurally characterized complex where the Schiff base is preserved at the expense of its thiazoline tautomeric form.
Ab Initio Studies on Disubstituted closo‐Icosahedral Heteroboranes, X2B10H10 [X = CH, SiH, N, P, and Sb]
Authors: Jemmis Eluvathingal D. , Kiran Boggavarapu , Coffey Dewitt
Published: July 2007

Ab initio theoretical studies on X2B10H10 (X = CH, SiH, N, P and Sb) have been done for all the three possible isomers. Unlike lower‐vertex heteroboranes, all the hetero derivatives have shown similar trends in the relative stabilities, the 1,12‐isomer being more stable followed by 1,7‐ and 1,2‐isomers, except for N and Sb. No conventional 1,2‐isomer for N could be found. Instead, a new nido isomer which is 18.1 kcal/mol higher in energy than the most stable isomer has been located. Any hetero group substitution to icosahedral R12H122− is found to be thermodynamically destabilizing. However, the Nucleus Independent Chemical Shift criterion shows that all compounds, except for 8, have similar aromaticity.
The Molecular Structures of Triaminosilanes
Authors: Huber Gerald , Mitzel Norbert W. , Schier Annette , Schmidbaur Hubert
Published: July 2007

The structural chemistry of a series of triaminosilanes XSi(NR2)3 has been investigated in order to determine the ground‐state configuration and conformation of these molecules. Theoretical studies and analogy with the isoelectronic XP(NR2)3 (X = CH2, O, Se, NSiMe3 etc.) and P(NR2)3 molecules suggest structures of Cs or C3 symmetry, with small energy differences between them. The molecular structure of HSi(NMe2)3 (1) has been determined by a single‐crystal X‐ray diffraction study at low temperature. Surprisingly, the molecules have a non‐standard conformation with an irregular orientation of the three NMe2 groups. The hydrido‐, chloro‐, methyl‐, and vinyltris(morpholino)silanes XSi[N(CH2CH2)2O]3 (X = H, Cl, Me, Vi; 2–5) were prepared from the corresponding chlorosilanes and morpholine (2, 3) or lithium morpholide (4,5). Their variable‐temperature NMR spectra were studied and the molecular structures determined by single crystal X‐ray diffraction. Compound 2 has a molecular geometry approaching mirror symmetry with one morpholino group significantly different from the other two. This structure resembles that of isoelectronic tris(amino)phosphines. Compounds 3–5 have structures with a propeller‐like arrangement of the three morpholino rings approaching C3 symmetry for this part of the molecules. The chloro compound 3 shows the shortest Si‐N bond lengths (average 1.690 Å), followed by 2 (1.708Å),5 (1.709Å) and 4 (l.712Å). The configuration of all nitrogen atoms is almost planar, with sums of the angles close to 360°, and the morpholino rings adopt a chair conformation. According to the solution NMR spectra the ring inversion is slow at low temperature, but the rings rotate freely about the Si‐N bonds on the NMR time scale. The molecular structures are discussed in terms of steric and electronic effects of the substituents. Other model compounds, including (Me2N)3SiC6H4‐4‐Br (6), MeSi[N(CH2CH2)2NMe]3 (7) and PhSi[N(CH2)4]3 (8), could not be crystallized, but were characterized by their analytical and spectroscopic data.
Organometallic Chemistry sans Organometallic Reagents: Modulated Electron‐Transfer Reactions of Subvalent Early Transition Metal Salts
Authors: Eisch John J. , Shi Xian , Alila Joseph R. , Thiele Sven
Published: July 2007

The potential of low‐valent, early transition‐metal reagents as selective reductants in organic chemistry has been foreshadowed by intensive research on the ill‐defined and heterogeneous subvalent titanium intermediates generated in the McMurry reaction and its numerous variants. As part of the long‐term research effort to develop soluble, well‐defined transition‐metal reductants of modulated and selective activity toward organic substrates, the THF‐soluble reductant, titanium dichloride, has been throughly examined, as well as the analogous ZrCl2 and HfCl2 reagents, all of which are readily obtainable by the alkylative reduction of the Group tetrachloride by butyllithium in THF. Noteworthy is that such interactions of MCl4 with butyllithium in hydrocarbon media lead, in contrast, to M(III) or M(IV) halide hydrides. Analogous alkylative reductions in THF applied to VCl4, CrCl3, and MoCl5 have yielded reducing agents similar to those obtained from Mcl4 but gradated in their reactivity. Such reductants have proved capable of coupling carbonyl derivatives, benzylic halides, acetylenes and certain olefins in a manner consistent with an oxidative addition involving a two‐electron transfer (TET). Such a reaction pathway is consistent with the observed stereochemistry of pinacol formation from ketones and for the reductive dimerization of alkynes. In contrast of the reaction of CrCl3 with two equivalents of butyllithium, which leads to a CrCl intermediate, the interaction of CrCl3 in THF with four equivalents of butyllithium at –78°C yields a reagent of the empirical formulation, LiCrH4.2LiCl.2 THF, as supported by elemental and gasometric analysis of its protolysis. This hydridic reductant cleaves a wide gamut of s̀ carbon–heteroatom bonds (C–X, C–O, C–S and C–N), towards which the CrCl reductant is unreactive. The type of cleavage and/or coupled products resulting from the action of “LiCrH4” on these substrates in best understood as arising from single‐electron transfer (SET). In light of the aforementioned findings, the gradated reducing action noted among TiCl2, HfCl2 and CrCl, as well as the contrasting reducing behavior between CrCl and LiCrH4, there is no doubt that future research with early transition metals will continue to yield novel reductants of modulated and site‐selective reactivity.
Photochemical Reactions of a Binuclear Naphthalene‐Manganese Complex with 2‐Butyne
Authors: Kreiter Cornelius G. , Georg Andreas , Reiß Guido J.
Published: July 2007

Pentacarbonyl(μ‐.4:6‐1,4‐dimethylnapthalene)dimanganese‐(Mn–Mn) (1), upon UV irradiation at 193 K in the presence of 2‐butyne (2), yields tetracarbonyl(μ‐.2:2‐2‐butyne)(μ−1,2,3,4‐.:1,4,4a,8a‐.‐1,4‐dimethylnaphthalene)dimanganese (3) and tricarbonyl(4a,6,7,8,8a‐.−5‐hydro‐1,4‐dimethylnapthalene)‐manganese (4). The tetracarbonyl complex 3 rearranges in solution at room temperature to give tetracarbonyl(μ‐.2:2‐2‐butyne)(μ−4a,5,8,8a‐.:5,6,7,8‐.−1,4‐dimethylnaphthalene)‐dimanganese (5). The complexes 3 and 5 were characterised by IR and NMR spectroscopy, and by mass spectrometry, and complex 4 by IR and NMR spectroscopy. The molecular structures of 3 and 4 were determined by single‐crystal X‐ray diffraction analyses.
Carbene Structure of Stable Acyl (Formyl) Anion Equivalents
Authors: Hill Christof , Bosold Ferdinand , Harms Klaus , Lohrenz John C. W. , Marsch Michael , Schmieczek Michael , Boche Gernot
Published: July 2007

3‐Lithiated 4‐tert‐butyl‐imidazol‐2‐ylidene, 3‐lithiated 4‐tert‐butyl‐thiazol‐2‐ylidene, and the ZnBr species of the latter, are shown to be stable carbenes by X‐ray crystal structure determination. The crystal data are confirmed by 13C‐NMR investigations in solution and quantum‐chemical calculations. The exceptional stability of the acyl anion equivalents is due to the p(.) stabilization of the carbene carbon atoms by the adjacent amino (thio) substituents, as is also the case in the structurally related stable carbenes, which have recently been isolated for the first time by A. J.Arduengo III et al., and in stable nitrenium ions, as found by our group.
The First Monofluorenyl Zirconium Trichloride
Authors: Van Der Zeijden Adolphus A. H. , Mattheis Chris , Fröhlich Roland
Published: July 2007

The monofluorenyl zirconium complex [(.(5):.1‐C13H8CH2CH2OMe)ZrCl2(μ‐Cl)]2, (2), has been obtained bby reaction of the respective fluorenyl lithium derivative with ZrCl4 in diethyl ether. A single‐crystal X‐ray structural analysis shows that 2 is a chloride‐bridged dimer, in which the fluorenyl ligand is bonded in a transitional tri‐ to pentahapto fashion. The relatively weak fluorenyl–zirconium bond is stabilized by intramolecular coordination of the ether sidechain attached to the fluorenyl backbone. Despite this, the bidentate ligand is easily detached upon dissolution of 2 in THF. Simultaneous ether cleavage produces spiro[cyclopropane‐1,9′‐fluorene].
Benzil Derivatives as Trapping Reagents for the Monomeric Alkylindium(i) Compound in–c(SiMe3)3
Authors: Uhl Werner , Keimling Sven Ume , Phol Siegfried , Saak Wolfgang , Wartchow Rudolf
Published: July 2007

The tetrahedral cluster compound tetrakis[[Tris(trimethylsilyl)methyl]indium(I)] 91) reacts in boiling n‐hexane with benzil derivatives (p‐X‐C6H4)C(O)(p‐X‐C6H4) (X = H, OMe, Br), to yield the 1,4‐cycloadditon products of the monomeric alkylindium(I), In–C(SiMe3)3, in which the In atoms are coordinated by a chelating enediolato ligand, to form a five‐membered InO2C2 heterocycle. As shown by two crystal structure determinations (X = H, OMe), the products are dimeric in the solid state, with a four‐membered In2O2 heterocycle in the molecular center and both C(SiMe3)3 groups, as well as both enediolato substitutents in a cis arrangement.
Cyclocarbonylation of Bicyclic Vinylcyclopropanes – Selective Generation of Seven‐Membered Enones
Authors: Schulze Matthias M. , Gockel Ulrich
Published: July 2007

The cyclic vinylcyclopropane 6a reacts at elevated temperatures with iron pentacarbonyl to selectively give the enone 7a in 52% yield. Reducing the reaction time provided the isomeric ketones 7a–b. Partial chromatographic separation of this mixture allowed the complete spectroscopic identification of 7b by 1H NMR. The structure of 7c was determined from selected spectral data of the mixture of 7a and 7c. For comparison, the methyl substituted derivate 6b was subjected to a carbonylation under the above conditions exclusively providing 8 ini 42% yield. A mechanistic rationale for the two different modes of ring opening is presented.
Regioselective Complexation of New Multiple Piperazine/Pyridine Ligands: Differentiation by 113Cd‐NMR Spectroscopy
Authors: Ratilainen Jari , Airola Karri , Kolehmainen Erkki , Rissanen Kari
Published: July 2007

Eleven novel piperazine containing open‐chain ligands L1–L11 were designed to offer symmetrical and asymmetrical complexation sites for metal ions and were synthesized by repetitive synthetic method. The divergent use of aromatic bishalomethyl and mono‐N‐alkylated piperazine compounds as spaces led toa series of long (up to M. W. = 836) oligomeric multidentate N‐ligands. Due to the lack of solid state methods for structure analysis, an NMR technique using 113 Cd nucleus as a probe in solution state was utilised. 113 Cd chemical shifts were observed to be dependend on the coordination site and similar coordination sites in different ligands gave characteristically similar 113 Cd chemical shifts. As a result 113 Cd‐NMR spectroscopy proved to be an excellent tool to distinguish between the structures of the different complexation sites on a nearly quantitative level.
Ambient‐Pressure Organic Superconductors κ‐(DMEDO‐TSeF)2[Au(CN)4](solv.): Tc Tuning by Modification of the Solvent of Crystallization
Authors: Shirahata Takashi , Kibune Megumi , Yoshino Hiroko , Imakubo Tatsuro
Published: July 2007

The unsymmetrical π donor dimethyl(ethylenedioxy)tetraselenafulvalene (DMEDO‐TSeF) has provided six new organic superconductors with a monovalent square‐planar [Au(CN)4]− ion and cyclic ethers as solvent of crystallization. The six new organic superconductors κ‐(DMEDO‐TSeF)2[Au(CN)4](solv.) [solv.=1,3‐dioxolane (DOL), 2,5‐dihydrofuran (DHF), tetrahydropyran (THP), 1,3‐dioxane (1,3‐DOX), 3,4‐dihydro‐2H‐pyran (DHP), or 1,4‐dioxane (1,4‐DOX)] are classified into two subphases κL and κ′ according to the differences in their space group symmetry. κL‐(DMEDO‐TSeF)2[Au(CN)4](solv.) (solv.=DOL, DHF, THP, 1,3‐DOX or DHP) crystallizes in the orthorhombic space group Pnma, and Tc of the κL phase varies by 1.7–5.3 K according to the size and shape of the solvent of crystallization. On the other hand, κ′‐(DMEDO‐TSeF)2[Au(CN)4](solv.) (solv.=DOL or 1,4‐DOX) crystallizes in the noncentrosymmetric monoclinic space group Cc. The κ′‐phase containing 1,4‐DOX shows superconductivity at 4.2 K, but the κ′‐phase containing DOL does not show superconductivity down to 1.4 K. Systematic investigation of the six new organic superconductors, together with the two previously reported superconductors κH‐ and κL‐(DMEDO‐TSeF)2[Au(CN)4](THF), revealed that the Tc of the present system is finely tunable by utilizing the effect of the solvent of crystallization.
Submaximal effort tolerance as a predictor of all‐cause mortality in patients undergoing cardiac rehabilitation
Authors: Feuerstadt, Paul , Chai, Andrew , Kligfield, Paul
Published: July 2007

Background

Submaximal effort tolerance is routinely available during cardiac rehabilitation, but its prognostic value in relation to underlying referral diagnosis is not known.

Hypothesis

Treadmill effort capacity during submaximal exercise training predicts all‐cause mortality after cardiac rehabilitation.

Methods

We followed 600 consecutive patients (450 men and 150 women, mean age 65 years) who were referred to a 12‐week outpatient program of cardiac rehabilitation; 37% had a prior myocardial infarction (MI), 44% had a recent percutaneous intervention (PCI), and 39% had history of coronary artery bypass surgery (CABG).

Results

There were 48 deaths during a mean follow‐up period of 1603 ± 822 days. By multivariate Cox analysis, exit MET activity was the most significant predictor of all‐cause mortality. In this model, each 1 MET increase in exit submaximal effort tolerance was associated with a 34% decrease in mortality (hazard ratio [HR] 0.66, 95% confidence interval 0.56–0.77) alone and 28% decrease after adjustment for age (HR = 0.72, confidence interval 0.60–0.85). Enty MET level also had predictive value. Subgroup analysis revealed that the predictive value of exit METs was limited to patients after recent CABG and with MI. None of the variables predicted death after PCI, in whom mortality was significantly lower than in the other groups.

Conclusions

Submaximal effort tolerance at completion of cardiac rehabilitation, and also at entry, is a strong and age‐independent predictor of mortality in patients who have had either recent CABG or MI without intervention, but not in patients after recent PCI. Copyright © 2007 Wiley Periodicals, Inc.
Cardiac manifestations of parasitic infections part 2: Parasitic myocardial disease
Authors: Franco‐Paredes Carlos , Rouphael Nadine , Méndez José , Folch Erik , Rodríguez‐Morales Alfonso J. , Santos José Ignacio , Hurst J. W.
Published: July 2007

This is part two of a three‐part series discussing parasites of the heart. In this section, we present an overview on parasitic diseases predominantly involving the myocardium. Copyright © 2007 Wiley Periodicals, Inc.
Laser capture‐microarray analysis of Lim1 mutant kidney development
Authors: Potter S. Steven , Hartman Heather A. , Kwan Kin M. , Behringer Richard R. , Patterson Larry T.
Published: July 2007

The Lim1 gene has essential functions during several stages of kidney development. In particular, a tissue‐specific knockout in the early metanephric mesenchyme results in the formation of the earliest nephron precursor, the renal vesicle, but failure of this structure to progress to the next stage, the comma‐shaped body. To better understand the molecular nature of this developmental arrest, we used a laser capture microdissection–microarray strategy to examine the perturbed gene expression pattern of the mutant renal vesicles. Among the genes found differently expressed were Chrdl2, an inhibitor of BMP signaling, the proapoptotic factor Bmf, as well as myob5, an atypical myosin that modulates chemokine signaling, and pdgfrl, which is important in epithelial folding. Of particular interest, the microarray data indicated that the Dkk1 gene, which encodes an inhibitor of Wnt signaling, was downregulated ninefold in mutants. This was confirmed by in situ hybridizations. It is interesting to note that Lim1 and Dkk1 mutant mice have striking similarities in phenoytpe. These results suggest that the Dkk1 gene might be a key downstream effector of Lim1 function. genesis 45:432–439, 2007. Published 2007 Wiley‐Liss, Inc.
Versatile Methodology to Synthesize Oxygen‐Bridged Nine‐ and Ten‐Membered Cycloalkanes by the Hypoiodite Reaction
Authors: Montaña Ángel M. , Ponzano Stefano , Kociok‐Köhn Gabriele , Font‐Bardia Mercè , Solans Xavier
Published: July 2007

C‐3 derivatives of 6‐hydroxy‐2,7‐dimethyl‐11‐oxatricyclo[6.2.1.02,6]undecan‐4‐one reacted with lead tetraacetate (LTA) and iodine to afford, in good yield, 1,7‐epoxycyclononanes, which are the result of a β‐fragmentation of the C2–C6 bond adjacent to the tertiary hydroxy group on C‐6. This β‐fragmentation is followed by a ring contraction from a ten‐ to a nine‐membered ring system, by a free‐radical addition to the carbonyl group on C‐4. The reaction of precursors (not functionalized on C‐3) with LTA and iodine produced a β‐fragmentation without any further structural rearrangement, affording 1,8‐epoxycyclodecanes. The transformation of the carbonyl group on C‐4 to acetate avoided radical additions and rearrangements affording, in high yield, the corresponding cyclodecanes. By this methodology, either 1,7‐epoxycyclononane or 1,8‐epoxycyclodecane could be synthesized, in good yield, by choosing the appropriate substitution pattern on C‐3 in the substrate.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
One‐Step Synthesis of Lumazine and Xanthine: First Co‐Crystal of Lumazine and Perchloric Acid with a Unique Monohydrated Hydronium Ion (H5O2+) Mediated Supramolecular Assembly of the Lumazine Dimer
Authors: Goswami Shyamaprosad , Maity Annada C. , Fun Hoong‐Kun
Published: July 2007

A perchloric acid mediated one‐step synthesis of lumazine derivatives from pterins and xanthine from guanine is reported. However, 2‐pivaloylamino derivatives of pterins underwent simple hydrolysis of the pivaloylamino group generating free pterin compounds, but the 2‐oxo derivatives, that is, the lumazine compounds, were not obtained. A novel supramolecular assembly is constructed by the unique hydrogen bonding of H5O2+ bridging two hydrogen‐bonded dimers of lumazine to form the co‐crystal 21 with aqueous perchloric acid. In contrast, N2‐pivaloyl‐6‐bromo‐5‐deazapterin was simply hydrolysed to form the protonated deazapterin 22, which forms a unique six‐membered cyclic hydrogen‐bonded structure leading to the generation of a polymeric supramolecular assembly. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Solvent‐ and Structure‐Dependent Regioselectivity in the Boron‐Mediated Aldol Reaction of 2‐(1,3‐Dioxolan‐2‐yl)ethyl Ethyl Ketones
Authors: Lanners Steve , Norouzi‐Arasi Hassan , Khiri Naima , Hanquet Gilles
Published: July 2007

The regioselectivity of the Chx2BCl/Et3N‐mediated (Chx = cyclohexyl) aldol reactions of ketones of general structure 2 has been studied and was shown to depend on both ketone structure and solvent. Useful levels of regioselectivity in favour of any of the two possible regioisomers were obtained in either pentane or diethyl ether. The relative configuration of the aldol products was assigned by 1H NMR studies of six‐membered‐ring derivatives. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Synthesis of Cyclopropanes via Organoiron Methodology: Stereoselective Preparation of Bi(cyclopropyl)s
Authors: Pandey Rajesh K. , Lindeman Sergey , Donaldson William A.
Published: July 2007

Cyclopropanation of [2‐(alkenyl)pentenediyl]Fe(CO)3 complexes (4) proceeds in a diastereoselective fashion to afford [2‐(cyclopropyl)pentenediyl]Fe(CO)3. The relative stereochemistry of the products was established by X‐ray crystallography. The diastereoselectivity is rationalized on approach of the cyclopropanation reagent on the sterically more exposed face of 4. Oxidatively induced reductive elimination afforded stereodefined bi(cyclopropyl)s. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Study of the enantioseparation of imazaquin and enantioselective degradation in field soils by CZE
Authors: Yi Fei , Guo Baoyuan , Peng Zhenlei , Li Haifang , Marriott Philip , Lin Jin‐Ming
Published: July 2007

A fast, simple, and sensitive CE method was developed to study the separation and degradation of imazaquin enantiomers in field soils. The parameters pH and concentration of the buffer electrolyte, type and concentration of the chiral selectors, applied voltage, and temperature of the CE system were investigated. Sodium hydrogen phosphate (50 mM) at pH 10.1 containing 30 mM hydroxypropyl‐β‐CD (HP‐β‐CD) was found to be the suitable BGE. The reliable determination for imazaquin enantiomers was obtained at 20 kV applied voltage, 15°C separation system, and detection at 214 nm. Under the optimal conditions, the LODs (S/N = 3) were 0.0097 and 0.0098 mg/kg; linearity ranged from 0.019 to 1.24 and 0.020 to 1.26 mg/kg for the first‐eluting peak of imazaquin (imazaquin‐I) and the second‐eluting peak of imazaquin (imazaquin‐II) in soil, respectively. The precision in terms of the percentage of RSD (%RSD) calculated from peak area was not greater than 5%. With the suitable characteristics of the present method, it was applied to the study of enantioselective degradation in field soil. According to the calculated values of the enantiomer ratio (ER) and the rate constant of degradation (k), the results suggested that the degradation rate of the two enantiomers were slightly different, and that the pH of the soil had a strong influence on the rate of degradation.
Recent accomplishments in the field of enantiomer separation by CEC
Authors: Preinerstorfer Beatrix , Lämmerhofer Michael
Published: July 2007

The present review intends to summarize recent developments in the field of enantioselective separations and analysis by CEC. It covers studies published in English language in common peer‐reviewed journals within the period between 2003 and 2006. Both, methods making use of chiral mobile phase additives as well as chiral stationary phases for electrochromatographic enantiomer separations, are reviewed. Achievements that have been made on the various column technologies, such as open‐tubular, particle‐packed, inorganic, organic and particle‐fixed (hybrid‐type) monolithic as well as molecularly imprinted polymer phases, are discussed.
The use of agent based modelling techniques in hydrology: determining the spatial and temporal origin of channel flow in semi‐arid catchments
Authors: Reaney S. M.
Published: July 2007

Information on the spatial and temporal origin of runoff entering the channel during a storm event would be valuable in understanding the physical dynamics of catchment hydrology; this knowledge could be used to help design flood defences and diffuse pollution mitigation strategies. The majority of distributed hydrological models give information on the amount of flow leaving a catchment and the pattern of fluxes within the catchment. However, these models do not give any precise information on the origin of runoff within the catchment. The spatial and temporal distribution of runoff sources is particularly intricate in semi‐arid catchments, where there are complex interactions between runoff generation, transmission and re‐infiltration over short temporal scales.

Agents are software components that are capable of moving through and responding to their local environment. In this application, the agents trace the path taken by water through the catchment. They have information on their local environment and on the basis of this information make decisions on where to move. Within a given model iteration, the agents are able to stay in the current cell, infiltrate into the soil or flow into a neighbouring cell. The information on the current state of the hydrological environment is provided by the environment generator. In this application, the Connectivity of Runoff Model (CRUM) has been used to generate the environment. CRUM is a physically based, distributed, dynamic hydrology model, which considers the hydrological processes relevant for a semi‐arid environment at the temporal scale of a single storm event. During the storm event, agents are introduced into the model across the catchment; they trace the flows of water and store information on the flow pathways. Therefore, this modelling approach is capable of giving a novel picture of the temporal and spatial dynamics of flow generation and transmission during a storm event. This is possible by extracting the pathways taken by the agents at different time slices during the storm.

The agent based modelling approach has been applied to two small catchments in South East Spain. The modelling approach showed that the two catchments responded differently to the same rainfall event due to the differences in the runoff generation and overland flow connectivity between the two catchments. The model also showed that the time of travel to the nearest flow concentration is extremely important for determining the connectivity of a point in the landscape with the catchment outflow. Copyright © 2007 John Wiley & Sons, Ltd.
Characterizing the variability of wood in streams: simulation modelling compared with multiple‐reach surveys
Authors: Meleason Mark A. , Davies‐Colley Rob J. , Hall Graeme M. J.
Published: July 2007

Wood abundance in streams is an indicator of its likely geomorphological and ecological importance. However, wood volume estimates can be highly variable, due in part to natural variability and the methodology used to characterize it. We measured wood volume in streams of similar sizes and riparian forest conditions using extended field surveys and simulation modelling. We surveyed a total of 3·1 km along four tributary streams of New Zealand's Waihaha River to obtain an estimate of wood volume in streams with similar basin positions (second order), forest types (podocarp/hardwood forest), disturbance histories (post volcanic eruption of Taupo ca. 180 AD) and stream sizes (2–3 m bankfull width). A ‘sliding window’ analysis was conducted whereby the wood volume was calculated for a ‘window’ (i.e., reach survey of fixed length) that was progressively moved upstream in 10 m increments. The resulting frequency distributions of wood volume were bimodal and represented the range and relative proportion of reach volumes possible from the wood surveys. The wood volume based on all streams surveyed (23 m3/100 m) was equivalent to the 64th percentile of the sliding window distribution, suggesting that a randomly placed study reach would be likely to underestimate wood volume. The bimodal distribution was attributed to the inclusion/exclusion of relatively large (≥10 m3), but rare (0·3 logs/100 m) logs. We also examined the variability of reach‐level wood volume estimates (200 m and 400 m) for the Waihaha tributaries using the model OSU StreamWood. The volume frequency distributions from the simulations were similar to those from the empirical approach, except that they were unimodal. We attribute the unimodal distribution to the greater number of reach‐scale estimates used in the simulations (n = 2000). The two independent approaches characterized the variation of wood volumes possible for this forest type and stream width. Copyright © 2007 John Wiley & Sons, Ltd.
Order series method for forecasting non‐Gaussian time series
Authors: Chuang Ming‐De , Yu Gwo‐Hsing
Published: July 2007

A new forecasting non‐Gaussian time series method based on order series transformation properties has been proposed. The proposed method improves Yu's method without using Hermite polynomial expansion to process nonlinear instantaneous transformations and provides acceptable forecasting accuracy.  Copyright © 2007 John Wiley & Sons, Ltd.
Estimating and forecasting the long‐memory parameter in the presence of periodicity
Authors: Bisognin C. , Lopes S. R. C.
Published: July 2007

We consider one parametric and five semiparametric approaches to estimate D in SARFIMA (0, D, 0)s processes, that is, when the process is a fractionally integrated ARMA model with seasonality s. We also consider h‐step‐ahead forecasting for these processes. We present the proof of some features of this model and also a study based on a Monte Carlo simulation for different sample sizes and different seasonal periods. We compare the different estimation procedures analyzing the bias, the mean squared error values, and the confidence intervals for the estimators. We also consider three different methods to choose the total number of regressors in the regression analysis for the semiparametric class of estimation procedures. We apply the methodology to the Nile River flow monthly data, and also to a simulated seasonal fractionally integrated time series.  Copyright © 2007 John Wiley & Sons, Ltd.
Forecasting real‐time data allowing for data revisions
Authors: Fukuda Kosei
Published: July 2007

A modeling approach to real‐time forecasting that allows for data revisions is shown. In this approach, an observed time series is decomposed into stochastic trend, data revision, and observation noise in real time. It is assumed that the stochastic trend is defined such that its first difference is specified as an AR model, and that the data revision, obtained only for the latest part of the time series, is also specified as an AR model. The proposed method is applicable to the data set with one vintage. Empirical applications to real‐time forecasting of quarterly time series of US real GDP and its eight components are shown to illustrate the usefulness of the proposed approach.  Copyright © 2007 John Wiley & Sons, Ltd.
Prevalence and common genotypes of HCV infection in Sudanese patients with hepatosplenic schistosomiasis
Authors: Mudawi H.M.Y. , Smith H.M. , Fletcher I.A. , Fedail S.S.
Published: July 2007

A cross‐sectional hospital based study was carried out at the National Center for Gastrointestinal and Liver Disease in Khartoum, Sudan to determine the prevalence, common genotypes and risk factors for hepatitis C virus infection in Sudanese patients with hepatosplenic schistosomiasis. A total of 176 patients with hepatosplenic schistosomiasis were tested for HCV antibodies and 4.5% of the samples were reactive. PCR was positive in 2.3% of cases and genotype 4 was the major genotype isolated with subtypes 4, 4e, and 4c/4d. It is concluded that HCV was of low seroprevalence in the study population and that parenteral antischistosomal therapy was not a significant risk factor in transmission of infection in the Sudan. J. Med. Virol. 79:1322–1324, 2007. © Wiley‐Liss, Inc.
Quantitative temporal‐spatial distribution of severe acute respiratory syndrome‐associated coronavirus (SARS‐CoV) in post‐mortem tissues
Authors: Tang Julian W. , To Ka‐Fai , Lo Anthony W.I. , Sung Joseph J.Y. , Ng H.K. , Chan Paul K.S.
Published: July 2007

Few post‐mortem studies have been performed on patients who have died from severe acute respiratory syndrome (SARS). No studies have examined how the SARS‐associated coronavirus (SARS‐CoV) loads in different organs with respect to time, post‐mortem. The aim of this study was to determine the quantitative temporal‐spatial distribution of SARS‐CoV in the post‐mortem tissue samples of seven patients. Quantitation of a house‐keeping gene, glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) was undertaken to standardize the amount of tissue tested. SARS‐CoV viral load and SARS‐CoV/GAPDH RNA ratio for each organ type were related to four time durations: onset of illness to death, death to post‐mortem tissue sampling, and total durations of treatment with ribavirin and hydrocortisone. The SARS‐CoV/GAPDH RNA ratio remained relatively stable in most organ tissue types for all these time durations. The ratio reached the highest value of equal to or greater than one for lung and small bowel, whereas those for heart, liver, spleen, and kidney were always less than one. It is concluded that SARS‐CoV viral loads in these organs remain relatively stable, post‐mortem. This quantitative assessment further supports SARS‐CoV has a specific tropism for the human respiratory and gastrointestinal tracts, which may be related to the density of SARS‐CoV receptors. J. Med. Virol. 79:1245–1253, 2007. © Wiley‐Liss, Inc.
The seroprevalence of IgG antibodies to human papillomavirus (HPV) types HPV‐16, HPV‐18, and HPV‐11 capsid‐antigens in mothers and their children
Authors: Marais Dianne J. , Sampson Candice C. , Urban Margaret I. , Sitas Freddy , Wiliamson Anna‐Lise
Published: July 2007

Human papillomavirus (HPV) types causing anogenital lesions and cancer are accepted as being sexually transmitted. The methods whereby children acquire these anogenital type HPV infections are unclear. The present study determined the prevalence of anti‐HPV‐16, HPV‐11 and HPV‐18 IgG antibodies in mothers and their children in an attempt to identify evidence of HPV transmission from mother to child. HPV virus‐like particles (VLP) VLP‐16, VLP‐11 and VLP‐18 were used in enzyme‐linked immunosorbent assay to identify IgG antibodies in serum from 100 mothers and their 111 children. Antibodies to VLP‐16, VLP‐11 and VLP‐18 were found in serum from 17%, 21% and 16% of mothers, respectively and seroprevalences were 9%, 11.7% and 9.9%, respectively amongst the children. Of the 111 children, 23 (20.7%) showed antibodies to one or more of the three HPV types tested. Seven of these (30.4%) HPV IgG positive children had the same antibodies to one or more HPV types as their mothers. The prevalence of HPV‐11 was similar in children of seropositive compared with seronegative mothers (14% and 11%, respectively). The prevalence of HPV‐16 and HPV‐18 was higher in children of seropositive mothers compared with seronegative mothers (for HPV‐16, 18% and 7%, respectively, P = 0.1, for HPV‐18, 19% and 8%, respectively, P = 0.2). None of these differences were statistically significant indicating a lack of correlation between antibodies in mothers and children and no evidence to support vertical or horizontal mother to child transmission of HPV infection. Indications were of multiple sources of HPV infection in the children. J. Med. Virol. 79:1370–1374, 2007. © 2007 Wiley‐Liss, Inc.
Salivary human herpesvirus 8 shedding in renal allograft recipients with Kaposi's sarcoma
Authors: Al‐Otaibi L.M. , Ngui S.L. , Scully C.M. , Porter S.R. , Teo C.G.
Published: July 2007

Renal allograft recipients in the Middle East are at high risk of developing Kaposi's sarcoma. This report describes the extent of oral human herpesvirus 8 shedding and the genomic diversity of the virus in five Saudi Arabian kidney transplantation patients in whom Kaposi's sarcoma had developed. PCR protocols were applied to amplify three fragments of the viral genome from whole‐mouth saliva, parotid saliva, buccal and palatal exfoliates, plasma, peripheral blood leukocytes and biopsy of the Kaposi's sarcoma lesion, and to quantify the viral load in whole‐mouth saliva. Viral DNA was detected in all plasma and biopsy samples, 80% of whole‐mouth saliva, 20% of each of the other oral samples, and none of the leukocyte samples. The viral load in the cell‐free fraction of whole‐mouth saliva ranged between approximately 1.2 × 103 and 2.2 × 106 genome‐copies/ml. Genotypically distinct viral strains were evident: intra‐lesionally in 1 patient; intra‐orally in one patient; between an oral sample and biopsy in two patients; and in four patients, between an oral sample and plasma, and between plasma and biopsy. Thus, in the patients studied, salivary shedding of human herpesvirus 8 was frequent and could be extensive, and they were prone to multiple infections. Measures to curtail salivary viral transmission to pre‐ and post‐transplantation patients might reduce the incidence of post‐transplantation Kaposi's sarcoma. J. Med. Virol. 79:1357–1365, 2007. © 2007 Wiley‐Liss, Inc.
Quasispecies analysis of novel HIV‐1 recombinants of subtypes A and G reveals no similarity to the mosaic structure of CRF02_AG
Authors: Powell Rebecca L.R. , Konings Frank A.J. , Nanfack Aubin , Burda Sherri , Urbanski Mateusz M. , Saa D. , Nyambi Phillipe N.
Published: July 2007

HIV‐1 circulating recombinant form (CRF) 02_AG is responsible for greater than 65% of HIV‐1 infections in Cameroon and is widespread across West and West‐Central Africa. The parental subtypes A1 and G cocirculate in this part of Africa, and high rates of infection predispose to the generation of AG unique recombinant forms (URFs). Little is known as to whether A1 and G can recombine and thrive in vivo with breakpoints other than those characteristic of CRF02_AG. In this study, six unique recombinant viruses of subtypes A1 and G were identified in two individuals in Cameroon. A 1.5 kb fragment of the reverse transcriptase (RT) region of pol (HXB2 location 2,612–4,159) and the entire env gene (HXB2 location 6,202–9,096) were evaluated by phylogenetic and breakpoint analyses. Each URF was found to have breakpoints different than CRF02_AG, indicating that A and G gene segments are functionally compatible with more than one pattern of recombination. Furthermore, contemporaneous, cultured viruses from these individuals were analyzed, revealing different proportions of URFs compared to those found in plasma, possibly indicating compart mentalization and/or phenotypic variation among the URFs. CRF02_AG emerged from West‐Central Africa to become a highly successful viral strain. As such, monitoring the spread of newly emerging AG recombinants is critical not only for understanding the epidemiology of HIV‐1, but also in the design of future therapeutics and vaccines appropriate to this part of Africa, and globally. J. Med. Virol. 79:1270–1285, 2007. © Wiley‐Liss, Inc.