bluuebunny/crossref_metadata_2025 huggingface dataset:
The pattern of MyoD and contractile protein localization in primary epaxial myotome reflects the dynamic progression of nascent myoblast differentiation
Authors: Yang Yagai , Ordahl Charles P.
Published: November 2005

The localization of contractile and regulatory proteins in early stages of epaxial primary myotome development was analyzed by immunofluorescence microscopy. Contractile proteins that appear in an ordered sequence in the rostro‐caudal axis of somite development were found to reiterate that sequence in the dorso‐medial‐to‐ventro‐lateral axis of primary epaxial myotome development. Pair‐wise localization of MyoD–titin, desmin–titin, and desmin–myosin defined three zones extending from the dermomyotome dorso‐medial lip (DML) into the primary myotome layer. Zones M1 and M2, which were positive for MyoD + titin and MyoD + titin + desmin, respectively, were restricted to the dorso‐medial‐most extremity of the myotome layer and did not expand during the course of myotome development. Zone M3 was positive for MyoD, desmin, titin, myosin, and cardiac troponin T and was the only zone that expanded during primary myotome development. Myotome fibers in zone M3 were unit‐length, spanning the full rostro‐caudal axis of the myotome while fibers in zones M1 and M2 were shorter than unit length. Anti‐myoD immunofluorescence, when detected in cells lacking contractile‐protein‐positive cytoplasm, was restricted to the DML and nascent myotome cells immediately subjacent to the DML. These results demonstrate a dynamic spatio‐temporal sequence in the differentiation program of nascent myotome cells as they emerge from the DML; zones M1 and M2 reflect standing waves of sequential contractile protein activation during the maturation of nascent myotomal myoblasts, while the expanding zone M3 reflects the accumulation of mature myotome fibers expressing a full cohort contractile proteins. Developmental Dynamics 235:382–394, 2006. © 2005 Wiley‐Liss, Inc.
Analysis of Meox‐2 mutant mice reveals a novel postfusion‐based cleft palate
Authors: Jin Jiu‐Zhen , Ding Jixiang
Published: November 2005

Cleft palate represents a common human congential disease involving defects in the development of the secondary palate. Major steps in mammalian palatogenesis include vertical growth, elevation, and fusion of the palate shelves. Our current study with the homeobox gene Meox‐2 during mouse secondary palate development reveals a novel postfusion‐based mechanism for cleft palate. Meox‐1 and Meox‐2 are two functionally related homeobox genes playing important roles in somitogenesis and limb muscle differentiation. We found that the expression of Meox‐2, not Meox‐1, marks the specification of early mouse palatal mesenchymal cells in the maxillary processes at embryonic day 11.5 (E11.5). From E12.5 to E15.5, the expression of Meox‐2 occupies only the posterior part of the palate, providing an early molecular marker for the anterior–posterior polarity in mouse secondary palate formation. A total of 35.3% of Meox‐2−/− (n = 17) and 25.5% of Meox‐2+/− (n = 55) mouse embryos display a cleft palate phenotype at E15.5, indicating that the reduction of Meox‐2 function is associated with susceptibility to cleft palate. Unlike previously reported clefts, none of the clefts found in Meox‐2 mutants contain any epithelial sheets in the medial edge areas, and detailed examination revealed that the clefts resulted from the breakdown of newly fused palates. This article is the first report of a gene required to maintain adherence of the palatal shelves after fusion. Developmental Dynamics 235:539–546, 2006. © 2005 Wiley‐Liss, Inc.
Development of the upper lip: Morphogenetic and molecular mechanisms
Authors: Jiang Rulang , Bush Jeffrey O. , Lidral Andrew C.
Published: November 2005

The vertebrate upper lip forms from initially freely projecting maxillary, medial nasal, and lateral nasal prominences at the rostral and lateral boundaries of the primitive oral cavity. These facial prominences arise during early embryogenesis from ventrally migrating neural crest cells in combination with the head ectoderm and mesoderm and undergo directed growth and expansion around the nasal pits to actively fuse with each other. Initial fusion is between lateral and medial nasal processes and is followed by fusion between maxillary and medial nasal processes. Fusion between these prominences involves active epithelial filopodial and adhering interactions as well as programmed cell death. Slight defects in growth and patterning of the facial mesenchyme or epithelial fusion result in cleft lip with or without cleft palate, the most common and disfiguring craniofacial birth defect. Recent studies of craniofacial development in animal models have identified components of several major signaling pathways, including Bmp, Fgf, Shh, and Wnt signaling, that are critical for proper midfacial morphogenesis and/or lip fusion. There is also accumulating evidence that these signaling pathways cross‐regulate genetically as well as crosstalk intracellularly to control cell proliferation and tissue patterning. This review will summarize the current understanding of the basic morphogenetic processes and molecular mechanisms underlying upper lip development and discuss the complex interactions of the various signaling pathways and challenges for understanding cleft lip pathogenesis. Developmental Dynamics 235:1152–1166, 2006. © 2005 Wiley‐Liss, Inc.
Transient T cell accumulation in lymph nodes and sustained lymphopenia in mice treated with FTY720
Authors: Morris Margaret A. , Gibb David R. , Picard Franck , Brinkmann Volker , Straume Marty , Ley Klaus
Published: November 2005

FTY720 (2‐amino‐2‐[2‐(4‐octylphenyl)ethyl]propane‐1,3‐diol hydrochloride) is an orally available immunomodulatory agent that induces severe peripheral blood lymphopenia. Most studies of these lymphopenic effects have been limited to short‐term exposure to FTY720. FTY720 alters the ability of lymphocytes to respond to sphingosine‐1‐phosphate (S1P) through S1P receptors, particularly S1P1. FTY720 affects different leukocyte populations and their trafficking through major lymphoid organs. We show the dynamics of CD4 T, CD8 T, and B lymphocyte recirculation in all major lymphoid compartments during 21‐day FTY720 treatment of normal C57BL/6 mice. Following a transient increase in peripheral lymph nodes and Peyer's patches, lymphocyte recirculation reaches a new steady state. Other lymphoid organs show transient changes in lymphocyte composition with various patterns. At 21 days of FTY720 treatment, total body lymphocyte content is reduced by 20% and blood lymphocytes by 80%. Modeling suggests that the new steady state is due to a combination of reduced naive lymphocyte release from the thymus and a transient reduction of lymphocyte egress from lymph nodes. Our data indicate that the commonly held belief that FTY720 blocks lymphocyte egress from lymph nodes cannot fully explain the lymphocyte dynamics observed with prolonged treatment.
The Escherichia coli heat‐labile enterotoxin induces apoptosis of immature lymphocytes in vivo via a glucocorticoid‐dependent pathway
Authors: Tamayo Esther , Merino Ramón , González‐Rojas Jovanna , Marquina Regina , Santiuste Inés , Amado José Antonio , Rappuoli Rino , Del Giudice Giuseppe , Merino Jesús
Published: November 2005

Escherichia coli heat‐labile enterotoxin (LT) exhibits a broad range of immunomodulatory activities, including the induction of lymphocyte‐programmed cell death. However, the nature of the lymphoid populations sensitive to LT‐induced apoptosis and the mechanisms used by this toxin to promote such activity are still unclear. In this study, we demonstrate that LT induces in mice a rapid increase in the levels of circulating corticosterone, resulting in a dramatic induction of cell death of immature CD4+CD8+, B220+IgM– and IgM+IgD– T and B cell progenitors, respectively. Apoptosis of these cell populations is similar to that reported after experimental treatment with corticosteroids, it is inhibited by mifepristone, a glucocorticoid receptor antagonist, and does not occur in adrenalectomized animals. These results clearly indicate that endogenous glucocorticoids are the mediators of the LT‐induced cell death, which involves Bcl‐2‐dependent apoptotic pathways. The LT‐mediated programmed cell death requires systemic exposure and the enzymatic activity of LT, since a mutant devoid of any enzymatic activity have no pro‐apoptotic effect at any dose tested.
Dynamic regulation of FoxP3 expression controls the balance between CD4+ T cell activation and cell death
Authors: Kasprowicz Deborah J. , Droin Nathalie , Soper David M. , Ramsdell Fred , Green Douglas R. , Ziegler Steven F.
Published: November 2005

The forkhead‐family transcription factor FoxP3 is important for the development and function of CD4+CD25+ regulatory T cells. While the overall phenotypic effects of FoxP3 expression are evident, the mechanism by which FoxP3 regulates T cell activation is not well understood. CD4+ T cells from mice that express a FoxP3 Tg are refractory to TCR‐mediated stimulation, failing to proliferate or produce cytokines, but possess suppressive activity towards normal T cells. In this report we show that these T cells express elevated levels of mRNA for pro‐apoptotic genes and undergo rapid apoptosis following stimulation. These T cells also display slower cell cycle transit following activation, suggesting that FoxP3 is capable of regulating the ability of T cells to respond to TCR‐mediated activation. Lastly, we show that contrary to expected results, under Th1 or Th2 driving conditions, CD4+ T cells from FoxP3 Tg mice differentiate into effector cells. Concomitant with differentiation is a loss of FoxP3 mRNA and protein. These data demonstrate that FoxP3 levels regulate T cell function, and that FoxP3 itself is dynamically regulated during effector T cell differentiation.
PD‐L2:PD‐1 involvement in T cell proliferation, cytokine production, and integrin‐mediated adhesion
Authors: Saunders Paul A. , Hendrycks Vana R. , Lidinsky William A. , Woods Melody L.
Published: November 2005

The B7 family member programmed death ligand 2 (PD‐L2) has been implicated in both positive and negative regulation of T cell activity. In this study, we demonstrate that on human T cells, PD‐L2 acts only as a negative regulator of T cell activity, inhibiting proliferation, IL‐2 production, and IFN‐γ production via its interaction with programmed death‐1 (PD‐1). This study also shows a novel role for PD‐1 in inhibiting β1 and β2 integrin‐mediated adhesion. PD‐L2 inhibition of T cell function involves modulation of the phosphoinositide 3‐OH kinase (PI 3‐K)/AKT and extracellular signal‐related kinase (ERK)/mitogen‐activated protein kinase (MAPK) pathways, with PD‐L2 inhibiting anti‐CD3‐induced AKT phosphorylation within minutes and ERK phosphorylation after hours. Analysis of phosphatase activity of Src homology 2 domain‐containing tyrosine phosphatase (SHP)‐1 and SHP‐2 in response to anti‐CD3 mAb or anti‐CD3 mAb + PD‐L2 stimulation revealed that while SHP‐1 phosphatase activity is not affected by stimulation, SHP‐2 phosphatase activity is significantly increased by anti‐CD3 mAb + PD‐L2 stimulation. Anti‐CD3 mAb + PD‐L2 stimulation also increased the level of SHP‐2 associated with the PD‐1 receptor. These results suggest that catalytically active SHP‐2 associated with the PD‐1 receptor is involved in modulating T cell function.
The effects of thymic selection on the range of T cell cross‐reactivity
Authors: Chao Dennis L. , Davenport Miles P. , Forrest Stephanie , Perelson Alan S.
Published: November 2005

Based on the results of a computational model of thymic selection, we propose a mechanism that produces the observed wide range of T cell cross‐reactivity. The model suggests that the cross‐reactivity of a T cell that survives thymic selection is correlated with its affinity for self peptides. In order to survive thymic selection, a T cell with low affinity for all self peptides expressed in the thymus must have high affinity for major histocompatibility complex (MHC), which makes it highly cross‐reactive. A T cell with high affinity for any self peptide must have low MHC affinity to survive selection, which makes it highly specific for its cognate peptide. Our model predicts that (1) positive selection reduces by only 17% the number of T cells that can detect any given foreign peptide, even though it eliminates over 95% of pre‐selection cells; (2) negative selection decreases the average cross‐reactivity of the pre‐selection repertoire by fivefold; and (3) T cells responding to foreign peptides similar to self peptides will have a lower average cross‐reactivity than cells responding to epitopes dissimilar to self.
Mast cells are required for optimal autoreactive T cell responses in a murine model of multiple sclerosis
Authors: Gregory Gregory D. , Robbie‐Ryan Michaela , Secor Virginia H. , Sabatino Joseph J. , Brown Melissa A.
Published: November 2005

Once considered to be of sole importance in allergy and parasitic infections, the role of mast cells in other pathologic and protective immune responses is becoming increasingly evident. We previously demonstrated that mast cells contribute to the severity of EAE, the rodent model of multiple sclerosis. Here we show that one mode of mast cell action is through effects on the autoreactive T cell response. Early indices of both peripheral CD4 and CD8 T cell activation, including IFN‐γ production and increases in CD44 and CD11a expression, are attenuated in mast cell‐deficient (W/Wv) mice after myelin oligodendrocyte glycoprotein35–55 priming when compared to WT animals. Reduced infiltrates of activated T cells in the central nervous system are also observed. Importantly, selective repletion of the mast cell compartment restores most T cell responses in the lymph nodes and the central nervous system, correlating with reconstitution of severe disease. The adoptive transfer of WT‐derived encephalitogenic T cells results in significantly less severe disease in W/Wv recipients, indicating that mast cells also exert potent effects after the initial T cell response is generated. Our data provide the first in vivo evidence that mast cells can significantly influence T cell responses and suggest that mast cells exacerbate disease during both the inductive and effector phases.
Synthesis of Main Group Polycations in Molten and Pseudo‐Molten GaBr3 Media
Authors: Kuznetsov Alexei N. , Popovkin Boris A. , Ståhl Kenny , Lindsjö Martin , Kloo Lars
Published: November 2005

The prospects of synthesizing polycationic species using GaBr3 in benzene solution at room temperature have been investigated. The salts Bi8[GaBr4]2, Sb8[GaBr4]2 and Te4[Ga2Br7]2 have been isolated and characterized. The first two compounds are isotypic with Sb8[GaCl4]2, crystallize in the space group Pna21, and feature square anti‐prismatic E82+ polycations (E = Sb, Bi). Unit‐cell parameters for Bi8[GaBr4]2 are a = 18.3014(10) Å, b = 10.3391(6) Å and c = 13.5763(7) Å, and for Sb8[GaBr4]2; a = 18.096(2) Å, b = 10.1572(9) Å and c = 13.2168(10) Å. Te4[Ga2Br7]2 crystallizes in the space group P21/c with a = 10.1600(9) Å, b = 10.8314(9) Å, c = 13.8922(10) Å and β = 99.182(7)°, and features a square‐planar Te42+ polycation. The compound Bi5[GaBr4]3 has been synthesized from molten GaBr3 and characterized by using powder diffractometry in space group Fm‐3c; a = 17.6263(8) Å. The structure model for this compound suggests the included Bi53+ cations to be practically freely oriented within its cavities in the solid phase. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthesis and Characterization of Two Novel, Mono‐Lacunary Dawson Polyoxometalate‐Based, Water‐Soluble Organometallic Ruthenium(II) Complexes: Molecular Structure of [{(C6H6)Ru(H2O)}(α2‐P2W17O61)]8–
Authors: Sakai Yoshitaka , Shinohara Akira , Hayashi Kunihiko , Nomiya Kenji
Published: November 2005

The synthesis and structural characterization of a novel class of mono‐lacunary Dawson polyoxometalate‐(POM‐)based, water‐soluble organometallic complexes, which are expected to be effective homogeneous oxidation catalyst precursors in water, is described. The organometallic complexes K8[{(C6H6)Ru(H2O)}(α2‐P2W17O61)]·12H2O (1) and K8[{(p‐cymene)Ru(H2O)}(α2‐P2W17O61)]·16H2O (2) were successfully prepared by direct reactions of the mono‐lacunary Dawson POM K10[α2‐P2W17O61]·19H2O with the organometallic precursors [(C6H6)RuCl2]2 and [(p‐cymene)RuCl2]2, respectively, in aqueous media and characterized by complete elemental analysis, thermogravimetric and differential thermal analyses (TG/DTA), and FT‐IR and solution (1H, 13C, 31P, and 183W) NMR spectroscopy. The molecular structure of [{(C6H6)Ru(H2O)}(α2‐P2W17O61)]8– (1a), in which the binding of the cationic organometallic group {(C6H6)Ru(H2O)}2+ occurs through two oxygen atoms of the four available oxygen atoms in the mono‐lacunary site of the POM, resulting in overall C1 symmetry, was successfully determined by single‐crystal X‐ray analysis. Interestingly, the hydrophilicity of the organometallic precursors is greatly enhanced by binding to a mono‐lacunary Dawson POM with higher hydrophilicity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis of Monodisperse CdS Nanospheres in an Inverse Microemulsion System Formed with a Dendritic Polyether Copolymer
Authors: Wang Fang , Xu Guiying , Zhang Zhiqing , Xin Xia
Published: November 2005

Nanosized CdS spheres with diameters of about 25, 40, and 50 nm have been synthesized in three inverse microemulsions formed with a dendritic amphiphilic copolymer (H2O/SD31/n‐butanol/n‐heptane) through the reaction of cadmium chloride (CdCl2) with the S2– ions that were slowly released from thioacetamide (TAA). X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), and UV/Vis absorption and photoluminescence (PL) spectroscopy were used to characterize the CdS nanospheres obtained. TEM and XRD studies showed that monodisperse CdS nanospheres with the zinc blende structure were produced, and the size of the CdS spheres increased with increasing water‐core size because of the increasing [water]/[dendrimer] mass ratio (ω). The blue‐shift of the maxima in the UV/Vis absorption and PL spectra indicated that the CdS spheres consisted of primary CdS nanocrystals showing a quantum confinement effect. The viscosities of the three microemulsions were also determined by rheological measurements. The viscosity of the inverse microemulsion system decreased as ω increased. The water core of the inverse microemulsion provided a soft template for the precipitation of CdS spheres.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Copper Complexes with (2,7‐Di‐tert‐butylfluoren‐9‐ylidene)methanedithiolate: Oxidatively Promoted Dithioate Condensation
Authors: Vicente José , González‐Herrero Pablo , García‐Sánchez Yolanda , Jones Peter G. , Bautista Delia
Published: November 2005

The reaction of [Cu(NCMe)4]PF6 with piperidinium 2,7‐di‐tert‐butyl‐9H‐fluorene‐9‐carbodithioate (pipH)[S2C(tBu‐Hfy)] (1; tBu‐Hfy = 2,7‐di‐tert‐butylfluoren‐9‐yl), affords [Cun{S2C(tBu‐Hfy)}n] (2), which reacts with various P ligands to give [Cu{S2C(tBu‐Hfy)}L2] [L = PPh3 (3a), PCy3 (3b), PiPr3 (3d); L2 = 1,1′‐bis(diphenylphosphanyl)ferrocene (dppf, 3c), bis(diphenylphosphanyl)methane (dppm, 3e)]. Compounds 3a–c react with atmospheric oxygen and moisture in the presence of NEt3 to give the dinuclear complexes [Cu2{[SC=(tBu‐fy)]2S}L2] [tBu‐fy = 2,7‐di‐tert‐butylfluoren‐9‐ylidene; L = PPh3 (4a), PCy3 (4b); L2 = dppf (4c)], which contain a new dithiolato ligand formally resulting from the condensation of two dithioato ligands with loss of a sulfide ion and two protons. Neutral CuI dithiolate complexes of the type [Cu4{S2C=(tBu‐fy)}2L4] [S2C=(tBu‐fy) = [2,7‐di‐tert‐butylfluoren‐9‐ylidene)methanedithiolate; L = PPh3 (5a), P(C6H4OMe‐p)3 (5b), PiPr3 (5d) or L2 = dppf (5c)] were obtained by treating 1 with [Cu(NCMe)4]PF6, the corresponding phosphane, and piperidine in a 1:2:2:1 molar ratio. The reaction of 1 with Cu(ClO4)2·6H2O and (Pr4N)OH in a 2:1:2 molar ratio gives the CuII complex (Pr4N)2[Cu{S2C=(tBu‐fy)}2] [(Pr4N)26], which readily oxidizes to the CuIII complex Pr4N[Cu{S2C=(tBu‐fy)}2] (Pr4N7) in the presence of atmospheric oxygen and moisture. The salt PPN7 [PPN+ =(Ph3P)2N+] was obtained from 1, CuCl2·2H2O, PPNCl, and piperidine in a 2:1:1:2 molar ratio under aerobic conditions. The crystal structures of 3a, 3c·CH2Cl2, 4a·4Me2CO, and 4c·CH2Cl2 have been determined by X‐ray diffraction studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Variable‐Valent Rhenium Chemistry of Conjugated Nitrogenous Ligands: Structure and Reactivity
Authors: Chakravorty Animesh
Published: November 2005

The valence states of particular concern in this review are VI–I and the ligand types are diimine, azoimine, imineamide and azooximeall bidentate and N,N‐coordinating. Metal reduction potentials and stability of oxidation states are subject to control via variation of the nature and extent of N,N‐chelation and coligation. Back‐bonding plays a major role in determining stability and isomer specificity, particularly in the valence domain III–I. Three types of mediated oxygen atom transfer processes have been scrutinized and modeled: from ReVO to tertiary phosphanes and variable‐spacer diphosphanes, from water to diimine and from oxime to metal/coligand. Other reactivity topics include isomerizations associated with ligand substitution, stable azo anion radical generation and azo cleavage. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
A New Coordination Polymer Architecture with (10,3)‐a Network Containing Chiral Hydrophilic 3‐D Channels
Authors: Zharkouskaya Aksana , Buchholz Axel , Plass Winfried
Published: November 2005

The triaminoguanidine‐based Schiff‐base ligand H5LOH reacts with copper(II) ions to afford a three‐dimensional coordination polymer with (10,3)‐a topology which is solely assembled by a single trigonal molecular building block {Cu3LOH}+. The unusual bridging mode of the phenolate oxygen atoms between the trigonal building blocks leads to a dihedral angle between the interlinked {Cu3LOH}+ units of 71°. The (10,3)‐a topology of the singular network results in a rather large void space of about 56 % that is established by interpenetrated chiral channels with a diameter limited by pseudo‐tetrahedral cavities defined by non‐coordinating phenolate hydroxy groups of the ligand. Additional information to establish the composition is derived from elemental analysis and TGA measurements. For the coordination polymer an overall antiferromagnetic behavior is observed. The spin‐frustrated trinuclear building blocks {Cu3LOH}+ are antiferromagnetically coupled via the bis(phenoxide)‐bridged dinuclear copper(II) moieties for which a dihedral angle of 132° is observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Dinuclear Lanthanide Schiff‐Base Complexes Forming a Rectangular Columnar Mesophase
Authors: Binnemans Koen , Lodewyckx Katleen , Cardinaels Thomas , Parac‐Vogt Tatjana N. , Bourgogne Cyril , Guillon Daniel , Donnio Bertrand
Published: November 2005

The Schiff base LH3 obtained by condensation of 3‐formyl‐4‐hydroxyphenyl‐3,4,5‐tris(tetradecyloxy)benzoate with 1,3‐diamino‐2‐propanol reacts with lanthanide(III) acetate salts to form dinuclear complexes of the type Ln2L2 with the trivalent ions from the first half of the lanthanide series (Ln = Nd, Sm, Gd). These stable and neutral metallomesogens exhibit a rectangular columnar mesophase over a broad temperature range. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
The Hexakis(thiocyanato)ferrate(III) Ion: a Coordination Chemistry Classic Reveals an Interesting Geometry Pattern for the Thiocyanate Ligands
Authors: Addison Anthony W. , Butcher Raymond J. , Homonnay Zoltán , Pavlishchuk Vitaly V. , Prushan Michael J. , Thompson Laurence K.
Published: November 2005

We are grateful to Professor Ulrich Müller, of Philipps‐Universität Marburg, for drawing the attention of ourselves and the referees to a prior structure report for (NMe4)3[Fe(NCS)6].1 The 1977 and 20052 reports differ only in the choice of unit cell origin. The conclusions from the structure–spectra relationships discussed in the 2005 paper remain the same.
Cycloadditions to Alkenyl[2.2]paracyclophanes
Authors: Aly Ashraf A. , Ehrhardt Sonja , Hopf Henning , Dix Ina , Jones Peter G.
Published: November 2005

Cycloadditions between the 4‐alkenyl[2.2]paracyclophanes 7, 16–21 and the dienophiles 10a–h have been studied. Whereas 10a, b, d, and g prefer Diels–Alder addition involving the olefinic double bond and one double bond of a cyclophane benzene ring, 10c, e, f, and h undergo other cycloadditions such as ene reaction (10c), [2+2] cycloaddition to the olefinic double bond (10e) and heterodiene addition to the vinyl substituent (10f, h). Several of the isolated cycloadducts (e.g. 24–26, 52) are valuable substrates for the preparation of annelated cyclophanes. The mechanisms of several of these cycloadditions are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Ketene Chemistry after 100 Years: Ready for a New Century
Authors: Tidwell Thomas T.
Published: November 2005

The existence of ketenes was established 100 years ago, and in recent years the pace of discovery in the study of these reactive intermediates has accelerated — extremely unstable ketenes such as difluoroketene have been directly observed for the first time, while a variety of bisketenes stabilized by silyl substituents have been isolated as long‐lived compounds at room temperature. New methods for generating ketenes for applications in synthesis have been devised, and these have been applied in the preparation of many valuable targets. Asymmetric synthesis by nucleophilic additions and by [2+2] cycloadditions to ketenes to form β‐lactams and β‐lactones has been achieved with high yields and high stereoselectivities. The free‐radical chemistry of ketenes is receiving increasing levels of attention, and new rearrangement reactions of ketenes have been developed. These advances create new opportunities to utilize the unique structures and high reactivity of ketenes for even greater progress in the future. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
One‐Pot Synthesis of Orthogonally Protected Enantiopure S‐(Aminoalkyl)cysteine Derivatives
Authors: Bolognese Adele , Fierro Olga , Guarino Daniela , Longobardo Luigi , Caputo Romualdo
Published: November 2005

The general synthesis of a new class of non‐natural diamino acids, 2‐amino‐3‐[(2′‐aminoalkyl)thio]propanoic acids or S‐(aminoalkyl)cysteines, is reported. Under the conditions devised, enantiopure N‐Boc‐protected β‐iodoamines, readily generated from proteinogenic α‐amino acids, are treated with L‐cysteine ethyl ester hydrochloride, using Cs2CO3 as a base. The S‐alkylation products, obtained in high yields (96–98 %) and without any detectable traces of accompanying byproducts, are hydrolysed to yield the free carboxyl group. An orthogonal protection is then introduced on the free amino group by treatment with Fmoc‐OSu under standard conditions. The inclusion of one of these orthogonally protected diamino acids in a solid‐phase growing pentapeptide is also reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Syntheses of O6‐Alkyl‐ and Arylguanine Derivatives: Nucleobase Adducts Derived from Styrene 7,8‐ and 3,4‐Oxides
Authors: Novák Jan , Hasník Zbyněk , Linhart Igor
Published: November 2005

A series of O6‐alkyl and ‐arylguanine derivatives that may be formed in vivo after exposure to styrene has been prepared by reaction of 6‐(4‐aza‐1‐azoniabicyclo[2.2.2]octyl)‐purine with alkoxides and aryloxides, respectively. Themonoprotected diols 2‐allyloxy‐ or 2‐benzyloxy‐1‐phenylethanol and 2‐allyloxy‐ or 2‐benzyloxy‐2‐phenylethanol were used as synthetic equivalents of styrene 7,8‐oxide. 4‐Vinylphenol, 2‐(4‐hydroxyphenyl)ethanol and 4‐hydroxyphenylacetic acid were used as synthetic equivalents of arene oxide metabolites of styrene, i. e., styrene 3,4‐oxide, 4‐(2‐hydroxyethyl)benzene 1,2‐oxide and 4‐carboxymethylbenzene 1,2‐oxide, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Ion‐Pairing Effects in the Self‐Assembly of a Fluorescent Pseudorotaxane
Authors: Clemente‐León Miguel , Pasquini Chiara , Hebbe‐Viton Virginie , Lacour Jerome , Dalla Cort Antonella , Credi Alberto
Published: November 2005

Herein we report on the self‐assembly, in a low polarity solvent, of a pseudorotaxane species comprising binaphthyl‐26‐crown‐8 (BN26C8) as the macrocyclic host and anthracenyl‐benzylammonium as the threadlike positively charged guest (ABH+). Absorption and luminescence data reveal a very efficient energy transfer process occurring from the binaphthyl to the anthracene singlet excited states. The self‐assembly is highly dependent on the nature of the counteranion confirming the crucial role played by it in the competition between the self‐assembly process and the formation of ion pairs (ABH+X–). This behavior can be readily evidenced in dilute solutions from the analysis of the luminescence properties of the system. The complexation of chloride, sulfate and hexafluorophosphate salts of ABH+ by racemic BN26C8 as well as the complexation of ABH+ salts of the chiral anion tris[tetrachlorobenzenediolato]phosphate(V) (TRISPHAT–) by (+)BN26C8 are described. The efficiency in complexation follows the trend PF6– > TRISPHAT– > Cl–, SO42–. The use of the chiral anion TRISPHAT allowed us to investigate the possibility of inducing stereoselective control on the formation of the interpenetrating assembly. Preliminary 1H NMR spectroscopic evidence supports the fact that the chiral anion is paired to the supramolecular complex and that its configuration influences the recognition process. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
NMR Enantiodiscrimination of Polar and Apolar Substrates by Multifunctional Cyclodextrins
Authors: Uccello‐Barretta Gloria , Balzano Federica , Sicoli Giuseppe , Scarselli Alessandro , Salvadori Piero
Published: November 2005

Mixed methylated/carbamoylated cyclodextrins constitute a new class of chiral complexing agents for NMR spectroscopy, which are able to induce anisochrony of enantiomeric mixtures of apolar trisubstituted allenes and polar derivatized compounds most of which are endowed with a π‐acidic 3,5‐dinitrophenyl ring. The differing contribution to enantiorecognition phenomena of the nature and location of the functional groups on the two cyclodextrin rims was shown. Some interesting aspects of the complexation phenomena, which are the basis of chiral recognition, have been underlined by NMR spectroscopic investigations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Substituent Effects on the Gas‐Phase Basicity of Formamidine Ureas
Authors: Díaz David D. , Finn M. G. , Mishima Masaaki
Published: November 2005

The gas‐phase basicities (GBs) for a representative set of six formamidine ureas with variations in the imino substituent [RN=CH–N(Me)C(O)NMe2] were determined in proton‐transfer equilibria by ion cyclotron resonance (ICR) mass spectrometry and further explored with calculations at the B3LYP/6‐31+G* level. The GB values, ranging from 218.6 to 230.9 kcal mol–1, were also compared with those previously reported for N1,N1‐dimethyl‐N2‐substituted formamidines. For all compounds investigated, protonation occurs preferentially at the imino nitrogen. In the cases of R = n‐C7H15, Ph(CH2)3 and Ph, no stable O‐protonated structures exist which can transfer proton to the N atom without a significant barrier. Relative GBs were linearly correlated to the inductive effect of the imine nitrogen substituents. The calculated structures are also given, and the calculated basicities are in good agreement with the observed values. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis and Electronic Properties of 3‐Acceptor‐Substituted and 3,7‐Bisacceptor‐Substituted Phenothiazines
Authors: Sailer Markus , Nonnenmacher Michael , Oeser Thomas , Müller Thomas J. J.
Published: November 2005

3‐Acceptor‐substituted and 3,7‐bisacceptor‐substituted phenothiazines can be synthesized in moderate to excellent yields through Suzuki cross‐coupling reactions between phenothiazin‐3‐yl pinacolyl boronates or phenothiazin‐3,7‐diyl bis(pinacolyl boronates) and electron‐deficient (hetero)aryl halides. The electronic properties of (hetero)aryl‐substitutedN‐methyl phenothiazines (UV/Vis absorption, fluorescence, redox potentials) can be correlated with the computed energies of the frontier molecular orbitals. Nitro‐substituted derivatives reveal electronically amphoteric behavior, displaying both reversible oxidations and reversible reductions. X‐ray structure analysis of the phenothiazinylp‐(2,5‐dinitro)phenylene‐bridged dyad13revealed donor–acceptor interactions between the molecules. Pyridyl and pyrimidyl derivatives fluoresce with quantum yields (Φf) of up to 49 % and can be regarded as redox‐active fluorophores. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Preparation of Conformationally Constrained α2‐Antagonists: The Bicyclo[3.2.0]heptane Approach
Authors: Bonnaud Bernard , Mariet Natacha , Vacher Bernard
Published: November 2005

The aim of this research was to discover α2‐receptor antagonist subtypes that are more selective than known compounds. We focused on rigid molecules possessing a benzo‐fused bicyclo[3.2.0]heptane skeleton. The synthetic route used relied upon the intramolecular [2+2] cycloaddition of styrylketene precursors. The cycloaddition was remarkably efficient and delivered multigram quantities of the cycloadduct 2. Studies of the removal of the ketone group in 2 revealed a facile opening of the four‐membered ring. Upon thermal elimination of TCI‐13‐endo (TCI = thiocarbonylimidazole) and TCI‐13‐exo, different products were obtaineddepending on the stereochemistry of the OH function of the precursor. Distinct mechanisms were proposed to account for the divergent outcomes observed. Double bond reductions from either methylcyclobutene or methylenecyclobutane isomers were thoroughly investigated in order to optimize the stereocontrol at the C‐1 position. Hydrogenation of the internal π‐bond produced an endo‐1‐methylcyclobutane derivative with high diastereoselectivity, whereas the exo‐1‐methyl isomer was best isolated by chromatographic separation of the acid 37. Finally, the prototypic imidazolidines 1, unsubstituted and bearing a methyl group at C‐1, were synthesized for biological evaluation.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis and Photophysical Studies of New Porphyrin–Phthalocyanine Dyads with Hindered Rotation
Authors: Tomé João P. C. , Pereira Ana M. V. M. , Alonso Cristina M. A. , Neves Maria G. P. M. S. , Tomé Augusto C. , Silva Artur M. S. , Cavaleiro José A. S. , Martínez‐Díaz M. Victoria , Torres Tomás , Rahman G. M. Aminur , Ramey Jeff , Guldi Dirk M.
Published: November 2005

A series of novel porphyrin–phthalocyanine (Por‐Pc) dyads1–3have been synthesized by using standard methodologies for unsymmetrically substituted phthalocyanine preparation. These two chromophoric units have been directly linked for the first time, that is, without any spacer, through the β‐pyrrolic position of ameso‐tetraphenylporphyrin, thus allowing a close proximity of the two units in a rigid arrangement. For this, a novel porphyrin–phthalonitrile precursor4had to be prepared. The UV/Vis spectra indicate that the basic electronic characteristics of both individual units (i. e., porphyrin and phthalocyanine) are retained in the hybrid Por‐Pc molecules. The short Por‐Pc separation in dyads1–3leads to strong excitonic coupling and ultrafast energy transfer (ca. 1012s–1), as determined by femtosecond transient absorption measurements, from the highly energetic1*(ZnPor) unit to the1*(ZnPc), which evolves to populate the long‐lived3*(ZnPc) by intersystem crossing. Interestingly, the energy transfer seems to occur more efficiently in dyads2and3, which have smaller HOMO–LUMO energy gaps. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
A Haigh–Mallion‐Based Approach for the Evaluation of the Intensity Factors of Aromatic Rings
Authors: Zonta Cristiano , De Lucchi Ottorino
Published: November 2005

A novel method for the determination of intensity factors of benzenoid systems based on the Haigh–Mallion (HM) theory has been developed. In this paper, the magnetic anisotropy generated by the ring‐current effect in polycondensed arenes has been quantitatively calculated as nuclear independent chemical shieldings (NICSs) in a three‐dimensional grid of points using the B3LYP/6‐31G(d) method implemented in the Gaussian 98 program. The fitting of the calculated values to the HM model gives intensity factors for each ring. A comparison of the obtained values with Schleyer’s NICS0 is given. The obtained intensity factors may find application in software using 1H NMR chemical shifts for structure determination.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis of the Tricyclic Core of Solanoeclepin A through Intramolecular [2+2] Photocycloaddition of an Allene Butenolide
Authors: Buu Hue B. T. , Dijkink Jan , Kuiper Sanne , van Schaik Sjoerd , van Maarseveen Jan H. , Hiemstra Henk
Published: November 2005

Studies are reported towards the synthesis of solanoeclepin A (1), the hatching agent of potato cyst nematodes. Two approaches are investigated to access the tricyclic core including the intricate bicyclo[2.1.1]hexanone moiety. The first approach is based on the intramolecular [2+2] photocycloaddition of dioxenone butenolide 10 and is shown to be less practical due to the limited synthetic utility of the photoproduct 11. The second approach uses as the key step the intramolecular [2+2] photocycloaddition reaction of allene butenolide 39. This latter photosubstrate is prepared through silver‐mediated coupling of silyloxyfuran 9 and allenic bromide 34. A five‐step sequence starting with the Baylis–Hillman reaction between benzyl butadienolate and paraformaldehyde leads to bromide 34. The crucial photocycloaddition of 39 proceeds with excellent regioselectivity and produces the adduct 40 in good yield. This methylenecyclobutane‐containing product 40 is deemed to contain the appropriate functionalities for future studies towards the natural product as is indicated through a model study leading to cyclobutanone 25. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Toward Novel Glyconjugates: Efficient Synthesis of Glycosylated 4‐Alkylidene‐‐lactams
Authors: Adinolfi Matteo , Galletti Paola , Giacomini Daria , Iadonisi Alfonso , Quintavalla Arianna , Ravidà Alessandra
Published: November 2005

A new class of glycoconjugated β‐lactams was accessed by direct glycosidation of a suitable 4‐alkylidene‐azetidin‐2‐one acceptor with several perbenzylated (N‐phenyl)trifluoroacetimidate donors activated by catalytic Yb(OTf)3. Goodstereocontrol was achieved by relying on the stereo directing effect of nitrile or ether solvents. Transfer hydrogenolysis under carefully controlled conditions enabled the removal of the benzyl group without affecting the β‐lactam double bond. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
New Functionalised Hydroxymethyl Ketones from the Mild and Chemoselective KMnO4 Oxidation of Chiral Terminal Olefins
Authors: Bonini Carlo , Chiummiento Lucia , Funicello Maria , Lupattelli Paolo , Pullez Maddalena
Published: November 2005

Various terminal olefinic compounds are directly converted into the corresponding α‐hydroxy ketones in good yields by potassium permanganate oxidation. The reaction is also highly chemoselective in the presence of differently protected hydroxy groups and can be utilised for the preparation of polyfunctional compounds such as polyols. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Cover Picture: Natural Product‐Guided Synthesis of a Spiroacetal Collection Reveals Modulators of Tubulin Cytoskeleton Integrity (Eur. J. Org. Chem. 22/2005)
Authors: Barun Okram , Kumar Kamal , Sommer Stefan , Langerak Anette , Mayer Thomas U. , Müller Oliver , Waldmann Herbert
Published: November 2005

The cover picture shows the stereoselective solid‐phase synthesis of highly substituted spiroketal molecules. Asymmetric aldol reactions on a solid phase are the key steps involved in this synthetic route. Both resin‐bound β‐hydroxy aldehydes and boron enolates were employed for syn‐ and anti‐aldol reactions, respectively. Out of this small collection of spiroacetals, some molecules showed activities against tubulin polymerization. The effect of two different spiroketals at a concentration of 5 μm on the tubulin cytoskeleton is shown in the picture (top right and bottom left). Furthermore, some spiroketals were found to be phosphatase inhibitors. Details are discussed in the article by H. Waldmann et al. on p. 4773 ff.
Rejection of wastewater‐derived micropollutants in high‐pressure membrane applications leading to indirect potable reuse
Authors: Drewes Jörg E. , Bellona Christopher , Oedekoven Matthew , Xu Pei , Kim Tae‐Uk , Amy Gary
Published: November 2005

The rejection of emerging organic micropollutants is an important issue where sources impaired by wastewater discharge are used to augment drinking water supplies. Because previous findings from bench‐ and laboratory‐scale membrane experiments indicated that nanofiltration and to a lesser extent reverse osmosis (RO) membranes can incompletely reject organic micropollutants, this study investigated the efficiency of reverse osmosis membranes in rejecting these compounds at conditions simulating full‐scale installations. Compounds investigated were classified by their physicochemical properties. Rejection of solutes was studied using a two‐stage laboratory membrane skid and two full‐scale RO trains. Full‐scale studies did not reveal any quantifiable detects of any target compound, except for low concentrations of caffeine in permeate samples of the second and third stages of one facility. In general, hydrophilic ionic compounds were efficiently removed by steric and electrostatic exclusion. Although there was no evidence that hydrophobic solutes such as steroid hormones partition into permeates, the rejection of chloroform at one facility was rather poor, confirming findings from laboratory‐scale experiments. Findings suggest that fouling layers present on membranes in full‐scale installations result in an improved rejection of hydrophilic nonionic and especially hydrophobic solutes. © 2005 American Institute of Chemical Engineers Environ Prog, 2005
Water recycling and desalination by air gap membrane distillation
Authors: Meindersma G. W. , Guijt C. M. , de Haan A. B.
Published: November 2005

Because salt and other small components are the most common compounds in wastewater from the process industry, desalination techniques are likely to be suitable as treatment processes in many cases. Although membrane distillation (MD) is a well‐known technology for desalination and water treatment, it is not yet applied in industry. Membrane distillation differs from other membrane technologies in that the driving force for desalination is the difference in vapor pressure of water across the membrane, rather than total pressure. The membranes for MD are microporous and hydrophobic, which allows water vapor (but not liquid water) to pass. The vapor pressure gradient is created by heating the source water, thereby elevating its vapor pressure.

The major energy requirement of MD is low‐grade thermal energy. It is expected that the total costs for water purification with membrane distillation will be lower than $0.50/m3, even as low as $0.26/m3, depending on the source of the thermal energy required for the evaporation of water across the membrane. Because low‐grade heat is readily available in industry, MD can very well be applied for desalination of process streams. © 2005 American Institute of Chemical Engineers Environ Prog, 2005
Extension of a high‐resolution scheme to 1D liquid–gas flow
Authors: García‐Cascales J. R. , Corberán‐Salvador J. M.
Published: November 2005

This paper presents the extension of a high‐resolution conservative scheme to the one‐dimensional one‐pressure six‐equation two‐fluid flow model. Only mixtures of water and air have been considered in this study, both fluids have been characterized using simple equations of state, namely stiffened gas for the liquid phase and perfect gas for the gas phase. The resulting scheme is explicit and first‐order accurate in space and time. A second‐order version of the scheme has also been derived using the MUSCL strategy and slope limiters. Some numerical results show the good capabilities of this type of schemes in the solution of discontinuities in two‐fluid flow problems, all of them are based on water/air numerical benchmarks widely used in the two‐phase flow literature. Copyright © 2005 John Wiley & Sons, Ltd.
Information content of cross‐sectional option prices: A comparison of alternative currency option pricing models on the Japanese yen
Authors: Dupoyet Brice
Published: November 2005

This article implements a currency option pricing model for the general case of stochastic volatility, stochastic interest rates, and jumps in an attempt to reconcile levels of risk‐neutral skewness and kurtosis with observed option prices on the Japanese yen and to analyze the information content of the cross section of option prices by investigating the hedging and pricing performance of various currency option pricing models. The study makes use of both a method of moments and a more traditional generalized‐least‐squares (GLS) estimation technique, taking advantage of the fact that methods of moments do not specifically require the use of cross‐sectional option prices, whereas GLS does. Results centered around the Asia economic crisis of 1997 and 1998 indicate that the cross section of option prices surprisingly does not appear to contain superior information as the two estimation techniques yield relatively similar results once idiosyncratic differences between them are acknowledged. Extensions of the G. Bakshi, C. Cao, and Z. Chen (1997) results to currencies are also provided. © 2006Wiley Periodicals, Inc. Jrl Fut Mark 26:33–59, 2006
Volatility options: Hedging effectiveness, pricing, and model error
Authors: Psychoyios Dimitris , Skiadopoulos George
Published: November 2005

Motivated by the growing literature on volatility options and their imminent introduction in major exchanges, this article addresses two issues. First, the question of whether volatility options are superior to standard options in terms of hedging volatility risk is examined. Second, the comparative pricing and hedging performance of various volatility option pricing models in the presence of model error is investigated. Monte Carlo simulations within a stochastic volatility setup are employed to address these questions. Alternative dynamic hedging schemes are compared, and various option‐pricing models are considered. It is found that volatility options are not better hedging instruments than plain‐vanilla options. Furthermore, the most naïve volatility option‐pricing model can be reliably used for pricing and hedging purposes. © 2006 Wiley Periodicals, Inc. Jrl Fut Mark 26:1–31, 2006