bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis, characterization and cytotoxic activity of new diorganotin(IV) complexes of N‐(3,5‐dibromosalicylidene)tryptophane
Authors: Tian Laijin , Liu Xicheng , Zheng Xiaoliang , Sun Yuxi , Yan Dongmei , Tu Linglan 
Published: January 2011

AbstractFour new diorganotin(IV) complexes of N‐(3,5‐dibromosalicylidene)tryptophane, R2Sn[3,5‐Br2‐2‐OC6H2CHNCH(CH2Ind)COO] [Ind = 3‐indolyl; R = Et (1); n‐Bu (2); Cy (3); Ph (4)], were synthesized and characterized by elemental analysis and IR, NMR (1H, 13C and 119Sn) spectra. The crystal structures of complexes 1–3 were determined by X‐ray single crystal diffraction. The tin atom is five‐coordinated and its coordination geometry is best described as an intermediate between trigonal bipyramidal and square pyramidal. Intermolecular weak interactions in the complexes 1–3 connect molecules into a one‐dimensional helical chain and a two‐dimensional array. The dibutyltin complex 2 has potent in vitro cytotoxic activity against two human tumor cell lines, CoLo205 and Bcap37, while the diethyltin complex 1 displays weak cytotoxic activity. Copyright © 2011 John Wiley & Sons, Ltd.
Energetic trade‐offs between brain size and offspring production: Marsupials confirm a general mammalian pattern
Authors: Isler Karin 
Published: January 2011

AbstractRecently, Weisbecker and Goswami presented the first comprehensive comparative analysis of brain size, metabolic rate, and development periods in marsupial mammals. In this paper, a strictly energetic perspective is applied to identify general mammalian correlates of brain size evolution. In both marsupials and placentals, the duration or intensity of maternal investment is a key correlate of relative brain size, but here I show that allomaternal energy subsidies may also play a role. In marsupials, an energetic constraint on brain size in adults is only revealed if we consider both metabolic and reproductive rates simultaneously, because a strong trade‐off between encephalization and offspring production masks the positive correlation between basal metabolic rate and brain size in a bivariate comparison. In conclusion, starting from an energetic perspective is warranted to elucidate relations between ecology, social systems, life history, and brain size in all mammals.
Alkaloid Diversity in Galanthus elwesii and Galanthus nivalis
Authors: Berkov Strahil , Bastida Jaume , Sidjimova Borjana , Viladomat Francesc , Codina Carles 
Published: January 2011

AbstractSeventy alkaloids of galanthamine, lycorine, homolycorine, tazettine, haemanthamine, narciclasine, and tyramine types were detected by GC/MS in 25 Galanthus elwesii and seven Galanthus nivalis populations, collected from different locations in Bulgaria. Intraspecies diversity in the alkaloid profiles regarding the main alkaloid types (chemotypes) was observed. Tyramine‐type protoalkaloids (namely, hordenine and its derivatives) were dominant in 19 populations of G. elwesii. In other populations of G. elwesii, the plants accumulated mainly homolycorine‐, lycorine‐, and galanthamine‐type alkaloids. The alkaloid profiles of G. nivalis were dominated by narciclasine‐, galanthamine‐, lycorine‐, haemanthamine‐, or tazettine‐type compounds. Geographical distribution of chemotypes indicated a relationship between populations, since adjacent populations often displayed similar alkaloid profiles. The results from year‐to‐year sampling and transplantation experiments imply genetic determination of alkaloid synthesis in the two studied species of Galanthus.
Four New Asterosaponins, Hippasteriosides A – D, from the Far Eastern Starfish Hippasteria kurilensis
Authors: Kicha Alla A. , Kalinovsky Anatoly I. , Ivanchina Natalia V. , Malyarenko Timofey V. , Dmitrenok Pavel S. , Ermakova Svetlana P. , Stonik Valentin A. 
Published: January 2011

AbstractFour new sulfated steroidal glycosides (asterosaponins), hippasteriosides A–D (1–4, resp.), were isolated from the alcoholic extract of the Far Eastern starfish Hippasteria kurilensis, collected in the Sea of Okhotsk near Kuril Islands. Compounds 1–4 were determined to contain the same unprecedented hexasaccharide moiety, β‐D‐xylopyranosyl‐(1→3)‐β‐D‐fucopyranosyl‐(1→2)‐β‐D‐quinovopyranosyl‐(1→4)‐[β‐D‐quinovopyranosyl‐(1→2)]‐β‐D‐xylopyranosyl‐(1→3)‐β‐D‐quinovopyranosyl, linked to C(6) of 3‐O‐sulfonylated steroidal aglycons, which differ from each other in their side‐chain structures. Structures 1–4 were elucidated by extensive NMR and MS techniques, and chemical transformations. Not all the asterosaponins show a prominent cytotoxic activity against human colon tumor HT‐29 cells, but some of them, especially compound 4 demonstrate a remarkable inhibition of the HT‐29 colony formation in soft‐agar clonogenic assay, suggesting its anticancerogenic properties.
Solid‐Phase Microextraction (SPME) Analysis of Six Italian Populations of Ephedra nebrodensisTineo ex Guss. subsp. nebrodensis
Authors: Maggi Filippo , Nicoletti Marcello , Petitto Valentina , Sagratini Gianni , Papa Fabrizio , Vittori Sauro 
Published: January 2011

AbstractHeadspace solid‐phase microextraction (HS‐SPME) coupled with GC/FID and GC/MS was applied for the first time in the analysis of the volatile fraction of an Ephedra species. Notably, six Italian populations (Marche, Abruzzo, and Sardinia) of Ephedra nebrodensis subsp. nebrodensis, covering almost the entire Italian area, were investigated to examine the chemical variability and to support the taxonomy of the species. A fiber screening with polymethylsiloxane (PDMS), CarboxenTM/polymethylsiloxane (CAR/PDMS), and polymethylsiloxane/divinylbenzene (PDMS/DVB) coatings, together with an optimization of the extraction conditions were carried out before analysis of the six populations. A total of 119 volatiles were identified in the headspace of different samples, accounting for 63.35–100.00% of the total volatiles. A great variability was found in the qualitative composition of different samples, since only 18 components were in common among all populations. The headspace composition was dominated by sesquiterpene hydrocarbons (52.30–88.32%), with β‐maaliene (traces–7.49%), β‐patchoulene (traces–1.29%), β‐panasinsene (traces–6.85%), α‐isocomene (traces–31.25%), α‐trans‐bergamotene (traces–6.95%), alloaromadendrene (traces–33.20%), α‐acoradiene (traces–9.41%), and γ‐muurolene (0.61–16.33%) being the most abundant constituents. Noteworthy is the occurrence in a sample of two major unknown sesquiterpenes, one hydrocarbon (24.49%, RI: 1396) and one oxygenated compound (10.37%, RI: 1591), whose mass spectra were reported for the first time. Multivariate chemometric techniques, such as cluster analysis (CA) and principal component analysis (PCA), were used to characterize the samples according to the geographical origin.
On the Mechanism of Eukaryotic Cell Penetration by α‐ and β‐Oligoarginines – Targeting Infected Erythro­cytes
Authors: Kamena Faustin , Monnanda Bopanna , Makou Danielle , Capone Stefania , Patora‐Komisarska Krystyna , Seebach Dieter 
Published: January 2011

AbstractFluorescein‐labeled α‐ and β‐octaarginine amides were synthesized. The route, by which these oligoarginine (OA) derivatives enter cells (hepatocytes, fibroblasts, macrophages), was investigated by confocal fluorescence microscopy. Comparisons (by co‐localization experiments) with compounds of known penetration modes revealed that the β‐octaarginine amide also uses multiple pathways to enter cells. There was no difference between the α‐ and the β‐OAs. Like other cell‐penetrating peptides (CPPs), the β‐octaarginine eventually winds up in the nucleoli of the cell nuclei (cf. Chem. Biodiversity, 2004, 1, 65). Surprisingly, there was no entry of α‐ or β‐OA into intact and healthy human erythrocytes (which do not possess a nucleus). Blood cells infected by Plasmodium falciparum (malaria parasite) were, however, entered readily, and the OAs went all the way through a couple of membranes into the parasite. The potential of these results for delivering specific antimalarial drugs directly into the parasite is discussed.
Enzymatic Dynamic Kinetic Resolution of Oxazinones: A New Approach to Enantiopure β2‐Amino Acids
Authors: Berkessel Albrecht , Jurkiewicz Ilona , Mohan Resmi 
Published: January 2011

AbstractIn the presence of Candida antarctica lipase B, the alcoholytic ring opening of 5‐substituted oxazinones proceeds as kinetic resolution (KR) and affords N‐acyl β2‐amino acid esters in up to 96 % ee, the remaining oxazinones were obtained in up to 99 % ee. In the presence of triethylamine as racemization catalyst, the enzyme‐catalyzed alcoholytic oxazinone opening proceeds as dynamic kinetic resolution (DKR), affording quantitative yields of N‐protected β2‐amino acid esters in high enantiomeric purity (up to 96 % ee). N,C‐double deprotection to afford the β2‐amino acid can be effected without loss of enantiopurity.
pH‐Switchable Inversion of the Metal‐Centered Chirality of Metallabenzenes: Opposite Stereodynamics in Reactions of Ruthenabenzene with L‐ and D‐Cysteine
Authors: Lin Ran , Zhang Hong , Li Shunhua , Chen Leiqi , Zhang Weiguang , Wen Ting Bin , Zhang Hui , Xia Haiping 
Published: January 2011

AbstractWe report herein the first study on the chemical interaction between metallabenzenes and bioactive molecules. Due to its unique stereoelectronic activities, a phenanthroline‐derived ruthenabenzene [Ru{CHC(PPh3)CHC(PPh3)CH}Cl(C12H8N2)(PPh3)]Cl2 (1) selectively binds cysteine in aqueous solution at physiological pH and then undergoes a dynamic inversion of configuration at the Ru center. The structure of the L‐cysteine‐binding product of 1 has been determined by means of X‐ray diffraction. The replacement of the L‐cysteine with the D form results in an inverted stereodynamic effect. Furthermore, the inversion process of the Ru‐centered configuration could be conveniently controlled by a simple pH adjustment. This is attributed to the significant influence of a special intramolecular electrostatic interaction on the dynamic epimerization process of the cysteine‐binding product.
Synthesis of a [2]Rotaxane Incorporating a “Magic Sulfur Ring” by the Thiol‐Ene Click Reaction
Authors: Zheng Haiyan , Li Yuliang , Zhou Chunjie , Li Yongjun , Yang Wenlong , Zhou Weidong , Zuo Zicheng , Liu Huibiao 
Published: January 2011

AbstractThe mild and highly efficient thiol‐ene click reaction has been used to construct a rotaxane incorporating dibenzo‐24‐crown‐8 (DB24C8) and a dibenzylammonium‐derived thread in high yield under the irradiation of UV light. A rotaxane containing a disulfide linkage in the macrocycle was also synthesized by the thiol‐ene click reaction. It has been demonstrated that the formation of the [2]rotaxane with the disulfide bond in the macrocycle occurs by a mechanism that is different to the threading‐followed‐by‐stoppering process. The successful construction of a rotaxane directly from its constituent components, the macrocycle containing a disulfide linkage and the dibenzylammonium hexafluorophosphate salt, suggests that the space within the macrocycle incorporating the disulfide linkage is smaller than the phenyl unit and a plausible reaction mechanism has been proposed as follows: A small amount of the initiator forms two radicals upon the absorption of UV irradiation; the radicals act as a “key” to “unlock” the disulfide bond in the macrocycle. The resulting crown ether like moiety in the macrocycle is clipped around the ammonium ion center in the dumb‐bell‐shaped compound. The [2]rotaxane is generated upon recombination of the disulfide linkage.
Rhythm Control for Management of Patients With Atrial Fibrillation: Balancing the Use of Antiarrhythmic Drugs and Catheter Ablation
Authors: Viles‐Gonzalez Juan F. , Fuster Valentin , Halperin Jonathan , Calkins Hugh , Reddy Vivek Y. 
Published: January 2011

AbstractAntiarrhythmic drug (AAD) therapy may be beneficial for patients with symptoms attributable to atrial fibrillation despite adequate rate control. The limited long‐term efficacy of AAD and the relatively large proportion of patients discontinuing therapy because of side effects led to the development of nonpharmacological therapies to achieve rhythm control. Pressing questions remain about the effect of ablation therapy on long‐term patient outcomes. Based on recent clinical trials and meta‐analyses, ablation appears more effective and possibly safer than AAD for long‐term maintenance of sinus rhythm in selected patients, but the evidence is insufficient to recommend ablation in preference to drug therapy as the first AAD therapy for the majority of patients in whom a rhythm control strategy is justified. Herein, we review the most current evidence supporting the use of AAD and catheter ablation in atrial fibrillation. Copyright © 2011 Wiley Periodicals, Inc.Hugh Calkins, MD is a consultant to Sanofi Aventis, Biosense Webster, and Medtronic, and he receives research support from Biosense Webster and Medtronic. All other authors have no conflicts of interest to disclose.
Offline enforcement of contracts for high‐performance computing
Authors: Damevski Kostadin 
Published: January 2011

AbstractDesign by contract is a well‐known software design methodology which enhances the quality of software through assertions expressed at the interface level. The overhead averse nature of High‐Performance Computing (HPC) applications often precludes the use of design by contract due to its potential overhead, especially when handling the large data sizes common in HPC. Our approach is to reduce the overhead of design by contract, by postponing (or offloading) across time and space the enforcement of contracts. We argue that the semantic implications of this approach are not significant, while leading to a large potential overhead reduction. A reduced overhead strategy to contract implementation may be necessary for a wider acceptance of this useful software engineering primitive. We apply our approach to contracts developed for software components based on the CCA (Common Component Architecture) model, which targets HPC applications. Copyright © 2011 John Wiley & Sons, Ltd.
N,N′‐Bis(2,2′‐bipyridine‐6‐ylmethyl)‐2,2′‐biphenylenediamines: A Tuneable Ligand Scaffold for Room Temperature Fe2+ SCO Complexes
Authors: Petzold Holm , Heider Silvio 
Published: January 2011

AbstractCondensation and subsequent reduction of 2,2′‐diaminobiphenyls 5 with 6′‐ and 5′‐substituted 6‐carbaldehyde‐2,2′‐bipyridines 4 yielded N,N′‐bis(2,2′‐bipyridine‐6‐ylmethyl)‐2,2′‐biphenyl‐enediamines 7, which were employed as hexadendate ligands with N6 donor sets in the synthesis of dicationic [Fe2+(7‐κ6N)] complexes 8. Dependent on the substitution pattern the respective complexes are found in the HS state (8b and 8c) or show SCO behaviour. By means of temperature‐dependent susceptibility measurements, usingEvans' method, the thermodynamic parameters ΔH, ΔS and T1/2 for the SCO have been determined. T1/2 as well as ΔH are remarkably susceptible to substitution next to the central C–C bond of the biphenyl bridge.
Flexible framework for the operation of distribution networks: synchronizing and connecting grid areas using multi back‐to‐back converters
Authors: de Graaff R. A. A. , Duarte J. L. , Kling W. L. , Vaessen P. T. M. 
Published: January 2011

AbstractDue to the unbundling of the electricity sector and simultaneously the growing interest in distributed generation, the uncertainty in operation and planning has increased for distribution network operators. To avoid uneconomic investments, flexible solutions are needed. For this, the concept of intelligent nodes is proposed, which is an application of multiple converters with back‐to‐back connections. This contribution addresses the control aspects for one of its specific operation conditions: the transition from supplying a radial feeder with loads and/or generation into controlling the power flow in a meshed network without loss of supply. The theoretical framework is described, followed by the measurement results of a laboratory‐scale demonstration. Copyright © 2011 John Wiley & Sons, Ltd.
Altered motor network activation and functional connectivity in adult tourette's syndrome
Authors: Werner Cornelius J. , Stöcker Tony , Kellermann Thilo , Bath Jessica , Beldoch Margarete , Schneider Frank , Wegener Hans Peter , Shah Jon N. , Neuner Irene 
Published: January 2011

AbstractTourette's syndrome (TS) is a developmental neuropsychiatric disorder characterized by motor and vocal tics as well as psychiatric comorbidities. Disturbances of the fronto‐striatal‐thalamic pathways responsible for motor control and impulse inhibition have been previously described in other studies. Although differences in motor performance are well recognized, imaging data elucidating the neuronal correlates are scarce. Here, we examined 19 adult TS patients (13 men, aged 22–52 years, mean = 34.3 years) and 18 age‐ and sex‐matched controls (13 men, aged 24–57 years, mean = 37.6 years) in a functional magnetic resonance imaging study at 1.5 T. We corrected for possible confounds introduced by tics, motion, and brain‐structural differences as well as age, sex, comorbidities, and medication. Patients and controls were asked to perform a sequential finger‐tapping task using their right, left, and both hands, respectively. Task performance was monitored by simultaneous MR‐compatible video recording. Although behavioral data obtained during scanning did not show significant differences across groups, we observed differential neuronal activation patterns depending on both handedness (dominant vs. nondominant) and tapping frequency in frontal, parietal, and subcortical areas. When controlling for open motor performance, a failure of deactivation in easier task conditions was found in the subgenual cingulate cortex in the TS patients. In addition, performance‐related functional connectivity of lower‐ and higher‐order motor networks differed between patients and controls. In summary, although open performance was comparable, patients showed different neuronal networks and connectivity patterns when performing increasingly demanding tasks, further illustrating the impact of the disease on the motor system. Hum Brain Mapp, 2011. © 2011 Wiley‐Liss, Inc.
Bismuth(III) Chloride‐Catalyzed Highly Efficient Transesterification of β‐Keto Esters
Authors: Sabitha Gowravaram , Srinivas Rangavajjula , Gopal Peddabuddi , Bhikshapathi M. , Singh Yadav Jhillu 
Published: January 2011

AbstractBismuth(III) chloride was found to be an efficient catalyst for the transesterification of a variety of β‐keto esters with a wide range of alcohols to afford transesterified products in good to high yields in short reaction times (see Table).
Reaction of 3‐Hydroxyquinoline‐2,4‐diones with Isocyanates and Thermally Induced Transformation of the Reaction Products
Authors: Mrkvička Vladimír , Lyčka Antonín , Vícha Robert , Klásek Antonín 
Published: January 2011

Abstract3‐Hydroxyquinoline‐2,4‐diones 1 react with isocyanates to give novel 1,2,3,4‐tetrahydro‐2,4‐dioxoquinolin‐3‐yl (alkyl/aryl)carbamates 2 and/or 1,9b‐dihydro‐9b‐hydroxyoxazolo[5,4‐c]quinoline‐2,4(3aH,5H)‐diones 3. Both of these compounds are converted, by boiling in cyclohexylbenzene solution in the presence of Ph3P or 4‐(dimethylamino)pyridine, to give 3‐(acyloxy)‐1,3‐dihydro‐2H‐indol‐2‐ones 8. All compounds were characterized by IR, and 1H‐ and 13C‐NMR spectroscopy, as well as by EI mass spectrometry.
First Synthesis of aC‐Homosteroid from Pregn‐4‐ene‐3,11,20‐trione
Authors: Zhang Zonglei , Wang Lizhong , Bian Xiaoqin , Sun Qian , Xu Hangxian , Wang Cunde 
Published: January 2011

Abstract(3α,5α)‐3‐Hydroxy‐C‐homopregnane‐11,20‐dione (3) was prepared in eleven steps from the commercially available pregn‐4‐ene‐3,11,20‐trione (4)viathe 11‐oxo‐13‐formyl‐12,13‐secopregnane intermediate11(Scheme 2). Subjection of this secopregnane to an intramolecular aldol condensation afforded theα,β‐unsaturated key intermediateC‐homopregn‐12‐en‐11‐one12.
Ypsilactosides A and B, Two New C22‐Steroidal Lactone Glycosides from Ypsilandra thibetica
Authors: Lu Yi , Xie Bai‐Bo , Chen Chang‐Xiang , Ni Wei , Hua Yan , Liu Hai‐Yang 
Published: January 2011

AbstractTwo new C22‐steroidal lactone glycosides, ypsilactosides A (1) and B (2), were isolated from the EtOH extract of the whole plant of Ypsilandra thibetica. Their structures were established as (3β,5α,16β,20S)‐3,16‐dihydroxy‐6‐oxopregnane‐20‐carboxylic acid γ‐lactone 3‐(β‐D‐glucopyranoside) (1) and (3β,16β)‐3,16‐dihydroxypregna‐5,20‐diene‐20‐carboxylic acid γ‐lactone 3‐{O‐α‐L‐rhamnopyranosyl‐(1→4)‐O‐α‐L‐rhamnopyranosyl‐(1→4)‐O‐[α‐L‐rhamnopyranosyl‐(1→2)]‐β‐D‐glucopyranoside} (2) on the basis of extensive spectroscopic analyses and chemical degradations.
Two New C20‐Diterpenoid Alkaloids from Aconitum carmichaelii
Authors: Shen Yong , Zuo Ai‐Xue , Jiang Zhi‐Yong , Zhang Xue‐Mei , Wang Hong‐Ling , Chen Ji‐Jun 
Published: January 2011

AbstractTwo new C20‐diterpenoid alkaloids, named aconicarchamines A and B (1 and 2, resp.), were isolated from Aconitum carmichaelii. By UV, IR, MS, and 1D‐ and 2D‐NMR analyses, their structures were elucidated as 14,17‐dihydro‐14,17‐dihydroxyajabicine and 15‐O‐acetyllassiocarpine. Compound 1 is the third C20‐diterpenoid alkaloid with the lycoctine skeleton bearing an exocyclic C‐atom at C(14).
Efficient Synthesis of [1,3]Oxazino[3,2‐f]phenanthridine Derivatives by a Novel 1,4‐Dipolar Cycloaddition Involving a Phenanthridine–Dimethyl Acetylenedicarboxylate Zwitterion and Aromatic Aldehydes
Authors: Li Ming , Pan Lei , Wen Li‐Rong 
Published: January 2011

AbstractAn efficient synthesis of [1,3]oxazino[3,2‐f]phenanthridine derivatives via a three‐component reaction of phenanthridine, dimethyl acetylenedicarboxylate (DMAD), and aromatic aldehydes is described. This novel method is complementary to the classical Huisgen 1,4‐dipolar cycloaddition in that it is well‐suited to the preparation of [1,3]oxazino[3,2‐f]phenanthridines.
Amaryllidaceae Alkaloids from Lycoris radiata
Authors: Feng Tao , Wang Yuan‐Yuan , Su Jia , Li Yan , Cai Xiang‐Hai , Luo Xiao‐Dong 
Published: January 2011

AbstractA phytochemical investigation on bulbs of Lycoris radiata resulted in the isolation of three new Amaryllidaceae alkaloids, named 5,6‐dehydrodihydrolycorine (1), 6β‐acetoxycrinamine (2), and (+)‐8‐O‐acetylhomolycorine α‐N‐oxide (3), together with eleven known alkaloids, 4–14. The structures of the new alkaloids were established by means of spectroscopic methods, and the known compounds were identified by comparison of their data with those in the literature. Compound 2 showed cytotoxicity against HL‐60, A‐549, and MCF‐7 cells, with IC50 values of 8.1, 24.3, and 15.0 μM, respectively.
Stereocontrolled Synthesis of Unnatural Tetrapeptides Containing L‐Valine Units. Part 3
Authors: Balducci Daniele , Porzi Gianni 
Published: January 2011

AbstractThe stereoselective synthesis of the new nonproteinogenic branched tetrapeptides 9a–9d and 15a,b, containing two L‐valine units and unnatural α‐amino acids, was accomplished starting from the chiral synthon 1a, a monolactim ether easily obtained from L‐valine.
Two‐Step Synthesis of 1,3‐Disubstituted 3,4‐Dihydro‐4‐thioxoquinazolin‐2(1H)‐ones from 1‐Bromo‐2‐fluorobenzenes
Authors: Kobayashi Kazuhiro , Komatsu Toshihide , Yokoi Yuki , Konishi Hisatoshi 
Published: January 2011

AbstractAn efficient synthesis of 3‐alkyl‐3,4‐dihydro‐4‐thioxobenzoquinazolin‐2(1H)‐ones 3 has been accomplished in two steps and in satisfactory yields from 1‐bromo‐2‐fluorobenzenes 1. Thus, the reaction of 1‐fluoro‐2‐lithiobenzenes, generated by the Br/Li exchange between 1 and BuLi, with alkyl isothiocyanates, gives N‐alkyl‐2‐fluorobenzothioamides 2, which, in turn, react with a series of isocyanates in the presence of NaH to give the desired products 3.