bluuebunny/crossref_metadata_2025_split huggingface dataset:
Toward an understanding of the factors responsible for the 1,2-migration of alkyl groups in borate complexes
Authors: Aggarwal Varinder K. , Fang Guang Yu , Ginesta Xavier , Howells Dean M. , Zaja Mirko 
Published: March 2006

Abstract
The anionotropic 1,2-migration of an organic substituent from a tetrasubstituted borate ion, often referred to as an "ate" complex, to an acceptor atom is at the basis of the most useful application of organoboranes in organic synthesis. We recently showed that chiral sulfur ylides react with boranes to give homologated products with high enantiomeric excess. In considering reactions with mixed boranes, the issue of which group would migrate arises. Although we are primarily interested in sulfur ylide reactions with boranes, in this review we have summarized the most important factors that are responsible for which group migrates from a broad spectrum of reactions involving borate complexes. We also discuss the use of blocking/nonmigrating groups and highlight when they are effective and not effective. Consideration of the most important factors that affect the outcome of which group migrates and understanding how and why blocking groups work, provides a strategy for designing boranes with nonmigrating groups for use in new reactions of these useful synthetic intermediates.
Photochemical release of various functional groups
Authors: Bochet Christian G. 
Published: March 2006

Abstract
The photochemical liberation of functional groups is an attractive alternative to the traditional chemical approach. Several photolabile protecting groups have been developed in the past decades, but they were mainly designed to protect amines and carboxylic acids. In this account, we present some of our recent work on the photochemical release of other functions, such as silanols, aldehydes, and ketones. We also describe a new form of differentiation among several photolabile groups by the use of monochromatic light tuned to each of them: the chromatic orthogonality.
GaCl3-catalyzed reactions utilizing isocyanides as a C1 source
Authors: Tobisu Mamoru , Oshita Masayuki , Yoshioka Sachiko , Kitajima Aki , Chatani Naoto 
Published: March 2006

Abstract
Two GaCl3-catalyzed reactions, which utilize isocyanides as a one-carbon unit, are described: a [4+1] cycloaddition of α,β-unsaturated carbonyl compounds with isocyanides, and an insertion reaction of isocyanides into a C-O bond of ketals and acetals. The relatively low affinity of GaCl3 toward heteroatoms enables the successful catalysis.
Catalytic activation of nitrogen derivatives with transition-metal complexes
Authors: Lebel Hélène , Leogane Olivier , Huard Kim , Lectard Sylvain 
Published: March 2006

Abstract
Studies regarding the transition-metal-catalyzed decomposition of nitrogen derivatives toward Curtius rearrangement and the formation of nitrenes which undergo C-H insertion and aziridination reactions are presented. These processes lead to the formation of C-N bond with a high level of selectivity and efficiency.
New technologies in catalysis using base metals
Authors: Lipshutz Bruce H. , Butler Tom , Frieman Bryan A. , Kogan Vladimir , Lee Ching-Tien , Lower Asher , Nihan Danielle M. , Taft Benjamin R. , Tomaso Anthony E. 
Published: March 2006

Abstract
Formation of C-C, C-N, and C-H bonds using three heterogeneous catalysts in the form of nickel-in-charcoal (Ni/C), nickel-on-graphite (Ni/Cg), and copper-in-charcoal (Cu/C) are described.
Synthesis of spiroketals by iridium-catalyzed double hydroalkoxylation
Authors: Messerle Barbara A. , Vuong Khuong Q. 
Published: March 2006

Abstract
A highly efficient approach to the synthesis of spiroketals involves the double cyclization of alkynyl diols using transition-metal catalysts. The iridium complex [Ir(PyP)(CO)2]BPh4 where PyP = 1-[(2-diphenylphosphino)ethyl]pyrazole is an effective catalyst for promoting the formation of spiroketals via this double hydroalkoxylation reaction. The complex promotes the formation of a series of spiroketal products from alkynyl diol starting materials such as 3-ethynylpentane-1,5-diol and 2-(4-hydroxybut-1-ynyl)benzyl alcohol. Stereoselective cyclization occurs for 3-ethynylpentane-1,5-diol, 3-ethynylhexane-1,6-diol. The cycloadditions occur in all but one case with quantitative conversion in under 24 h at 120 °C.
Chiral Ru/PNNP complexes in catalytic and stoichiometric electrophilic O- and F-atom transfer to 1,3-dicarbonyl compounds
Authors: Bonaccorsi Cristina , Althaus Martin , Becker Claus , Togni Antonio , Mezzetti Antonio 
Published: March 2006

Abstract
The asymmetric hydroxylation and fluorination catalyst [Ru(OEt2)2(PNNP)]2+ (PNNP = chiral tetradentate ligand with a P2N2 donor set) reacts with 1,3-dicarbonyl compounds to give dicationic adducts and, upon deprotonation, the corresponding enolato complexes. The relevance of these species to catalytic O- and F-transfer is investigated.
Alkoxy- and hydroxycyclization of enynes catalyzed by Pd(II) and Pt(II) catalysts
Authors: Michelet Véronique , Charruault Lise , Gladiali Serafino , Genêt Jean-Pierre 
Published: March 2006

Abstract
The development of a novel reaction ideal in terms of atom economy was achieved. The scope of the reaction was evaluated in the presence of Pd and Pt catalysts. The first enantioselective Pt-promoted enyne carboalkoxycyclization was developed in up to 85 % stereoselectivity. This ideal atom-economical reaction afforded the corresponding functionalized five-membered carbo- and heterocycles in good to excellent yields. The use of silver salts combined with (R)-Ph-BINEPINE, a monophosphane atropisomeric ligand, was found to be the best-suited combination for moderate to high enantioselectivities on carbonated and nitrogenated substrates.
Dual Lewis acid - Lewis base activation in enantioselective additions to aldehydes
Authors: Wingstrand Erica , Lundgren Stina , Penhoat Maël , Moberg Christina 
Published: March 2006

Abstract
Reaction of benzaldehyde with ethyl cyanoformate in the presence of Lewis acidic Ti(IV) complexes of bispyridylamide or salen ligands and Lewis basic amines affords the O-alkoxycarbonylated cyanohydrin. In the presence of the salen-based catalytic system, acetyl cyanide can also be added to benzaldehyde, providing a highly enantioselective direct route to the O-acetylated cyanohydrin.
Indium-catalyzed addition of carbon units to acetylenes: Development of a new C-C bond formation toward exploitation of chemical resources
Authors: Nakamura Masaharu 
Published: March 2006

Abstract
This account deals with an overview of the development of catalytic addition reactions of carbonyl compounds to alkynes catalyzed by a variety of indium salts. The new C-C bond formation reactions provide a powerful tool for α-functionalization of carbonyl compounds, including direct α-vinylation with acetylene, regioselective α-alkenylation, and α-ynenylation that can be applied to a modular synthesis of α-arylated β-keto esters.
New synthetic reactions catalyzed by cobalt complexes
Authors: Yorimitsu Hideki , Oshima Koichiro 
Published: March 2006

Abstract
Without suffering from β-elimination, cobalt complexes allow cross-coupling reactions of alkyl halides with Grignard reagents. A combination of a cobalt complex and trimethylsilylmethyl Grignard reagent effects Mizoroki-Heck-type reaction of alkyl halide with styrene, which conventional palladium catalysts have never made possible. Cobalt exhibits intriguing catalytic activities on hydrophosphination and allylzincation of alkynes. Silylmethylcobalt reagent is a powerful tool for the synthesis of highly silylated ethenes.
Catalytic asymmetric ring-opening of cyclopentadiene - heterodienophile cycloadducts with organometallic reagents
Authors: Pineschi Mauro , Del Moro Federica , Crotti Paolo , Macchia Franco 
Published: March 2006

Abstract
An unprecedented catalytic asymmetric ring-opening of easily accessible 2,3-heterosubstituted norbornenes with hard alkyl metals (R-M), is able to give a practical regio- and stereoselective access to hetero-functionalized alkyl cyclopentenes in an enantioenriched form. The copper-catalyzed desymmetrization reaction with trialkylaluminums of sterically hindered and rigid, tri- or tetracyclic Diels-Alder adducts, easily available by cycloaddition reaction of cyclopentadiene with 4-phenyl-urazole and 2,3-phthalazine-1,4-dione, proved to be particularly efficient. Interestingly, the chirality of the amine part of the BINOL-based phosphoramidite is able to impose the absolute stereochemistry of the corresponding adducts.
Helicity control in the synthesis of helicenes and related compounds
Authors: Starý Ivo , Stará Irena G. , Alexandrová Zuzana , Sehnal Petr , Teplý Filip , Šaman David , Rulíšek Lubomír 
Published: March 2006

Abstract
Asymmetric synthesis of helicenes and their congeners has been demonstrated to rely either on enantioselective Ni0/PR3
*-catalyzed [2+2+2] cycloisomerization of triynes or on diastereoselective CoI-catalyzed [2+2+2] cycloisomerization of chiral triynes. The former approach providing tetrahydrohelicenes in a nonracemic form requires further development as moderate enantioselectivities (up to 54 % ee) have so far been achieved under kinetic control. The latter approach affording helicene-like structures in a diastereomerically enriched form allows for reaching good to excellent diastereoselectivities (up to 100:0) under thermodynamic control.
Rhodium-catalyzed asymmetric hydrogenation using self-assembled chiral bidentate ligands
Authors: Takacs James M. , Chaiseeda Kittichai , Moteki Shin A. , Reddy D. Sahadeva , Wu Di , Chandra Kusumlata 
Published: March 2006

Abstract
The chirality-directed self-assembly of bifunctional subunits around a structural metal - typically, zinc(II) - is used to form a heteroleptic complex in which a second set of ligating groups are suitably disposed to bind a second metal, forming a heterobimetallic catalyst system. We find that subtle changes in the structural backbone (i.e., ligand scaffold) of such chiral bidentate self-assembled ligands (SALs) can be used to manipulate the ligand topography and chiral environment around catalytic metal; thus, the scaffold can be optimized to maximize asymmetric induction. Using this combinatorial strategy for ligand synthesis, a preliminary study was carried out in which a library of 110 SALs was evaluated in the rhodium-catalyzed asymmetric hydrogenation of a simple N-acyl enamide. The level of enantioselectivity obtained varies from near racemic to greater than 80 % ee as a function of the ligand scaffold, with the possibility of further improvement yet to be explored.
Dabbling with air-stable organoaluminum species
Authors: Biswas Kallolmay , Chapron Alex , Cooper Thea , Fraser Paul K. , Novak Andrew , Prieto Oscar , Woodward Simon 
Published: March 2006

Abstract
Highly stereoselective 1,2-additions of AlMe3 or its air-stable analog DABCO(AlMe3)2 to aldehydes are realized in the presence of a Ni(acac)2-derived catalyst using phosphoramidite ligands giving sec-alcohols in up to 95 % ee. Very high turnover number (TON) (>1500) and turnover frequency (TOF) (>350 h-1) values can be realized in these reactions. The substrate range, trials of various (DABCO)
a
(AlR3)
b
reagents (a = 0.1; b = 1.2; R = Me, Et, Bu
i
), ligands, and molecular modeling studies are used to propose a working model for the catalytic cycle and the origin of the stereoselectivity. The phosphoramidite ligand is proposed to bind the nickel in an η2 manner via the P-donor and one of the C=C aryl bonds of the CHAr amine group. Preliminary studies indicate that DABCO(AlMe3)2 can also be used as a methyl source in Pd-catalyzed cross-coupling reactions of ArX (X = Br, I) species.
Asymmetric protonation of silyl enolates catalyzed by chiral phosphine-silver(I) complexes
Authors: Yanagisawa Akira , Touge Taichiro , Arai Takayoshi 
Published: March 2006

Abstract
A catalytic asymmetric protonation of trimethylsilyl enolates was achieved using a 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP)-silver(I) fluoride complex as a chiral catalyst in a mixed solvent consisting of dichloromethane and methanol. Various nonracemic ketones possessing a tertiary asymmetric carbon at the α-position were prepared with high enantioselectivity up to 99 % ee.
In Vitro Formation of Enteric Neural Network Structure in a Gut-Like Organ Differentiated from Mouse Embryonic Stem Cells
Authors: Takaki Miyako , Nakayama Shinsuke , Misawa Hiromi , Nakagawa Tadashi , Kuniyasu Hiroki 
Published: March 2006

Abstract
Using an embryoid body (EB) culture system, we developed a functional organ-like cluster—a “gut”—from mouse embryonic stem (ES) cells (ES gut). Each ES gut exhibited spontaneous contractions but did not exhibit distinct peristalsis-like movements. In these spontaneously contracting ES guts, dense distributions of interstitial cells of Cajal (c-kit [a transmembrane receptor that has tyrosine kinase activity]-positive cells; gut pacemaker cells) and smooth muscle cells were discernibly identified; however, enteric neural ganglia were absent in the spontaneously differentiated ES gut. By adding brain-derived neurotrophic factor (BDNF) only during EB formation, we for the first time succeeded in in vitro formation of enteric neural ganglia with connecting nerve fiber tracts (enteric nervous system [ENS]) in the ES gut. The ES gut with ENS exhibited strong peristalsis-like movements. During EB culture in BDNF+ medium, we detected each immunoreactivity associated with the trk proto-oncogenes (trkB; BDNF receptors) and neural crest marker, proto-oncogene tyrosine-protein kinase receptor ret precursor (c-ret), p75, or sox9. These results indicated that the present ENS is differentiated from enteric neural crest-derived cells. Moreover, focal stimulation of ES guts with ENS elicited propagated increases in intracellular Ca2+ concentration ([Ca2+]i) at single or multiple sites that were attenuated by atropine or abolished by tetrodotoxin. These results suggest in vitro formation of physiologically functioning enteric cholinergic excitatory neurons. We for the first time succeeded in the differentiation of functional neurons in ENS by exogenously adding BDNF in the ES gut, resulting in generation of distinct peristalsis-like movements.
Non-invasive molecular imaging and reporter genes
Authors: Serganova Inna , Moroz Ekaterina , Moroz Maxim , Pillarsetty Nagavarakishore , Blasberg Ronald 
Published: March 2006

AbstractMolecular-genetic imaging in living organisms has become a new field with the exceptional growth over the past 5 years. Modern imaging is based on three technologies: nuclear, magnetic resonance and optical imaging. Most current molecular-genetic imaging strategies are “indirect,” coupling a “reporter gene” with a complimentary “reporter probe.” The reporter transgene usually encodes for an enzyme, receptor or transporter that selectively interacts with a radiolabeled probe and results in accumulation of radioactivity in the transduced cell. In addition, reporter systems based on the expression of fluorescence or bioluminescence proteins are becoming more widely applied in small animal imaging. This review begins with a description of Positron Emission Tomography (PET)-based imaging genes and their complimentary radiolabeled probes that we think will be the first to enter clinical trials. Then we describe other imaging genes, mostly for optical imaging, which have been developed by investigators working with a variety of disease models in mice. Such optical reporters are unlikely to enter the clinic, at least not in the near-term. Reporter gene constructs can be driven by constitutive promoter elements and used to monitor gene therapy vectors and the efficacy of gene targeting and transduction, as well as to monitor adoptive cell-based therapies. Inducible promoters can be used as “sensors” to monitor endogenous cell processes, including specific intracellular molecular-genetic events and the activity of signaling pathways, by regulating the magnitude of reporter gene expression.
Curcumin Analogs as Potent Aldose Reductase Inhibitors
Authors: Du Zhi‐Yun , Bao Ya‐Dan , Liu Zhong , Qiao Wei , Ma Lin , Huang Zhi‐Shu , Gu Lian‐Quan , Chan Albert S. C. 
Published: March 2006

AbstractIn the present study, curcuminoids isolated fromcurcuma longawere demonstrated to possess inhibitory activities on bovine lens aldose reductase. In order to find more potent aldose reductase inhibitor, curcumin analogs were synthesized and evaluated for their ability to inhibit bovine lens aldose reductase enzyme. The results indicated that the compounds with tetrahydroxyl groups, 2,6‐bis(3,4‐dihydroxybenzylidene)cyclohexanone (A2), 2,5‐bis(3,4‐dihydroxybenzylidene)cyclopentanone (B2), 1,5‐bis(3,4‐dihydroxyphenyl)‐1,4‐pentadiene‐3‐one (C2), and 3,5‐bis(3,4‐dihydroxybenzylidene)‐4‐piperidone (D2) showed remarkably potent inhibitory effects on aldose reductase with IC50of 2.9 μM, 2.6 μM, 3.4 μM, and 4.9 μM, respectively. The structure‐activity relationship revealed that the curcumin analogs withortho‐dihydroxyl groups could form a more tight affinity with aldose reductase to exert more potential inhibitory activities.
A Study of Anti‐inflammatory Activity of Some Novel α‐Amino Naphthalene and β‐Amino Naphthalene Derivatives
Authors: Sharma Shalabh , Singh Tripti , Mittal Rajan , Saxena K. K. , Srivastava Virendra Kishore , Kumar Ashok 
Published: March 2006

AbstractIn the present study, some naphthalene derivatives have been synthesized by incorporating azetidinyl and thiazolidinyl moieties at its α‐ or β‐positions such as α‐(3‐chloro‐2‐oxo‐4‐substituted)aryl‐1‐azetidinyl)naphthalenes 6–10, α‐((substituted)aryl‐4‐oxo‐1,3‐thiazolidin‐3‐yl)naphthalenes 11–15, β‐(3‐chloro‐2‐oxo‐4‐substituted aryl‐1‐azetidinyl)naphthalenes 21–25, and β‐(substituted aryl‐4‐oxo‐1,3‐thiazolidin‐3‐yl)naphthalenes 26–30. These compounds have also been screened for acute toxicity and anti‐inflammatory and analgesic activities. Compounds which showed better anti‐inflammatory and analgesic activities were also examined for their ulcerogenic liability and underwent a cyclooxygenase assay. Two compounds, 12 and 28, were found to exhibit potent anti‐inflammatory activity as compared to the standard drugs phenylbutazone and naproxen.
Electrochemical High‐Content Screening of Nitric Oxide Release from Endothelial Cells
Authors: Borgmann Sabine , Radtke Ina , Erichsen Thomas , Blöchl Andrea , Heumann Rolf , Schuhmann Wolfgang 
Published: March 2006

AbstractRelease of nitric oxide (NO) is of high importance for regulating endothelial cell functions during vasodilatation, vascular remodeling, and angiogenesis. Thus, a direct and reliable real‐time method for NO detection that takes into account time‐dependent variations of the NO concentration in the complex reaction within the diffusion zone above the cells is vital for obtaining information about the role of NO in intracellular endothelial signal transduction and its impact on the surrounding cells. In this study, the time course of vascular endothelial growth factor E (VEGF‐E) stimulated NO release from transformed human umbilical vein endothelial cells (T‐HUVEC) was investigated by means of metalloporphyrin‐based NO sensors employed in an electrochemical robotic system. The NO sensor was obtained by electrochemically induced deposition of NiIItetrakis(p‐nitrophenylporphyrin) on a 50‐μm diameter platinum disk electrode which was integrated, together with a 25‐μm diameter platinum disk, in a double‐barrel electrode arrangement. The second electrode was used as a guidance sensor for the automatic and highly reproducible positioning of the NO sensor at a known distance from a layer of adherently growing cells by usingz‐approach curves in the negative feedback mode of scanning electrochemical microscopy (SECM). The electrochemical robotic system allows the fully automated detection of NO with high sensitivity and selectivity to be performed in real time within 96‐well microtiter plates. A functional cell assay was established to allow the standardized detection of NO released upon stimulation from T‐HUVEC with a sensor positioned at a known distance above the endothelial cells. The overall system was evaluated by automatic detection of NO release from T‐HUVEC upon stimulation with VEGF‐E after incubation with a variety of drugs that are known to act on different sites in the complex signal‐transduction pathway that finally invokes NO release.
Impact of the Guanidinium Group on Hybridization and Cellular Uptake of Cationic Oligonucleotides
Authors: Deglane Gaëlle , Abes Saïd , Michel Thibaut , Prévot Paul , Vives Eric , Debart Françoise , Barvik Ivan , Lebleu Bernard , Vasseur Jean‐Jacques 
Published: March 2006

AbstractThe grafting of cationic groups to synthetic oligonucleotides (ONs) in order to reduce the charge repulsion between the negatively charged strands of a duplex or triplex, and consequently to increase a complex's stability, has been extensively studied. Guanidinium groups, which are highly basic and positively charged over a wide pH range, could be an efficient ON modification to enhance their affinity for nucleic acid targets and to improve cellular uptake. A straightforward post‐synthesis method to convert amino functions attached to ONs (on sugar, nucleobase or backbone) into guanidinium tethers has been perfected. In comparison to amino groups, such cationic groups anchored to α‐oligonucleotide phosphoramidate backbones play important roles in duplex stability, particularly with RNA targets. This high affinity could be explained by dual recognition resulting from Watson–Crick or Hoogsteen base pairing combined with cationic/anionic backbone recognition between strands involving H‐bond formation and salt bridging. Molecular‐dynamics simulations corroborate interactions between the cationic backbones of the α‐ONs and the anionic backbones of the nucleic acid targets. Moreover, ONs with guanidinium modification increased cellular uptake relative to negatively charged ONs. The cellular localization of these new cationic phosphoramidate ONs is mainly cytoplasmic. The uptake of these ON analogues might occur through endocytosis.
The attribution of blame scale with an incarcerated sample: factor structure, reliability and validity
Authors: Fazio Roberto Di , Kroner Daryl G. , Forth Adelle E. 
Published: March 2006

AbstractThe factor structure, reliability and validity of the Attribution of Blame Scale (ABS) were examined in a sample of 323 incarcerated violent offenders. Principal component analysis of the items resulted in a two‐factor solution of external and internal attribution in contrast with the original scales of victim, offender, alcohol, and societal blame. Measures of alcohol abuse, perception of external control and psychopathy corresponded with external attribution. The two‐factor structure of the ABS meets some basic psychometric properties for measuring criminal attributions within an offender population. Copyright © 1997 Whurr Publishers Ltd.