bluuebunny/crossref_metadata_2025 huggingface dataset:
Lipophilicity of some guaianolides isolated from two endemic subspecies of Amphoricarpos neumayeri (Asteraceae) from Montenegro
Authors: Atrrog Abubaker A. B. , Natić Maja , Tosti Tomislav , Milojković‐Opsenica Dušanka , Đorđević Iris , Tešević Vele , Jadranin Milka , Milosavljević Slobodan , Lazić Milan , Radulović Siniša , Tešić Živoslav
Published: September 2008

In this study 10 guaianolide‐type sesquiterpene γ‐lactones named amphoricarpolides, isolated from the aerial parts of two endemic subspecies of Amphoricarpos neumayeri (ssp. neumayeri and ssp. murbeckii Bošnjak), were investigated by means of reversed‐phase thin‐layer chromatography. Methanol–water and tetrahydrofuran–water binary mixtures were used as mobile phase in order to determine lipophilicity parameters R
 and C0. Some of the investigated compounds were screened for their cytotoxic activity against HeLa and B16 cells. Chromatographically obtained lipophilicity parameters were correlated with calculated logP values and IC50 values. Principal component analysis identified the dominant pattern in the chromatographically obtained data. Copyright © 2008 John Wiley & Sons, Ltd.
High‐performance liquid chromatographic determination of creatine kinase activity influenced by methylglyoxal
Authors: Peng Xiaofang , Ma Jinyu , Cheng Ka‐Wing , Chen Bo , Chen Feng , Wang Mingfu
Published: September 2008

Protein glycation has been implicated in the development of diabetic complications and other health disorders, which mainly arise from accumulation of advanced glycation endproducts (AGEs) in vivo. Methylglyoxal (MGO), a typical reactive intermediate carbonyl formed in early glycation process, can react non‐enzymatically with N‐terminal amino groups on proteins, leading to their inactivation and generation of detrimental AGEs. Recently, it was reported that activity of creatine kinase (CK, EC 2.7.3.2) could be reduced or even eliminated completely after incubation with MGO in vitro. CK activity is usually determined by conventional colorimetric assays. However, these methods are not appropriate for monitoring the influence of MGO on CK activity since MGO can also directly react with creatine, a substrate of CK. In this study, an efficient and much more accurate HPLC approach was established to investigate the effect of MGO on CK activity. Aminoguanidine was utilized to eliminate interference from the undesirable reaction between residual MGO and creatine. It was found that higher concentrations of MGO and longer incubation time for CK and MGO caused more pronounced reduction in CK activity. This HPLC method greatly facilitates acquisition of kinetic data about CK reaction and through further improvement it may be adopted to rapidly screen potential inhibitors of MGO‐induced glycation. Copyright © 2008 John Wiley & Sons, Ltd.
Measurement of xenobiotics in saliva: is saliva an attractive alternative matrix? Case studies and analytical perspectives
Authors: Mullangi Ramesh , Agrawal Shrutidevi , Srinivas Nuggehally R.
Published: September 2008

The use of saliva for measuring xenobiotic concentrations has been practiced for a number of years. While the use of saliva has been generally reserved for the analysis of diagnostic and forensic/toxicology samples, attempts have been made to further enhance the value of saliva as an alternate matrix to those of plasma and serum. It is understood that saliva represents a handy tool for therapeutic drug monitoring (TDM) as it offers certain distinctive advantages. This scope of this review encompasses the following: (a) a comprehensive view of saliva as an alternate matrix for either plasma or serum to understand the pharmacokinetic/pharmacodynamic (PK/PD) characteristics; (b) an account of the factors contributing to the observed variability in salivary monitoring; (c) a tabular compilation of diverse case studies of xenobitoics belonging to different therapeutic classes with emphasis on assay methodology and applicable analytical/biopharmaceutical/pharmacokinetic findings; (d) relevant thoughts on assay procedures as they relate to salivary monitoring; and (e) some representative case studies highlighting the new thinking on the use of saliva outside of traditional TDM. Overall, based on the review, saliva represents a valuable TDM tool for a number of xenobiotics. While parent compound and phase I metabolite(s) for many xenobiotics have been generally quantifiable in saliva, phase II metabolites have not generally been detected in saliva. Therefore saliva samples could also be used to answer some specific PK/PD questions during the drug development process, if applicable. However, the development and validation of the assay in saliva needs to be carried out carefully with particular focus on proper sample collection, processing and storage to ensure the stability of the xenobiotics and with the same rigor as applied to plasma, serum and urine matrices. Copyright © 2008 John Wiley & Sons, Ltd.
Determination of bergenin in human plasma after oral administration by HPLC‐MS/MS method and its pharmacokinetic study
Authors: Wang Jin , Wang Ben‐jie , Wei Chun‐min , Yuan Gui‐yan , Zhang Rui , Liu Hui , Zhang Xiu‐mei , Guo Rui‐chen
Published: September 2008

A highly sensitive, simple and selective high‐performance liquid chromatography–tandem mass spectrometry (HPLC‐MS/MS) method was developed and applied to the determination of bergenin concentration in human plasma. Bergenin and the internal standard (IS) thiamphenicol in plasma were extracted with ethyl acetate, separated on a C18 reversed‐phase column, eluted with mobile phase of acetonitrile–water, ionized by negative ion pneumatically assisted electrospray and detected in the multi‐reaction monitoring mode using precursor → product ions of m/z 327.1 → 192 for bergenin and 354 → 185.1 for the IS, respectively. The linear range of the calibration curve for bergenin was 0.25–60 ng mL−1, with the lowest limit of quantification of 0.25 ng mL−1, and the intra/inter‐day relative standard deviation (RSD) was less than 10%. The method is suitable for the determination of low bergenin concentration in human plasma after therapeutic oral doses, and has been first and successfully used for its pharmacokinetic studies in healthy Chinese volunteers. Copyright © 2008 John Wiley & Sons, Ltd.
The sustainability spectrum and the sciences of sustainability
Authors: Seager Thomas P.
Published: September 2008

Understanding sustainability requires integrating multiple perspectives and investigative methods to explain multidimensional concepts. However, the traditional approach to research and education is organized along disciplinary lines that tend to exclude awareness of contributions in one field that may inform problems in another. This presents a serious obstacle to advancing an understanding of sustainability, which is focused on the interactions between industrial and ecological systems, rather than examining each system independently. This paper offers a broad description of different perspectives with regard to sustainability including security, reliability, resilience and renewal, and briefly describes the emerging sciences essential to understanding sustainability: ecological economics, industrial ecology, ecosystem health, and sustainable decision making, policy and design. In the latter, the challenges have yet to find an academic locus. Nonetheless, it is in this area that knowledge of sustainability science must be applied and it is consequently most proximate to business leaders, policy makers and designers. Copyright © 2008 John Wiley & Sons, Ltd and ERP Environment.
Dendritic Nucleotides: Interaction with an Aliphatic Acid Monolayer
Authors: Wang Guojie , Abramov Mikhail , Van Aerschot Arthur , Rozenski Jef , Lei Shengbin , Klymchenko Andrei , Van der Auweraer Mark , De Feyter Steven , Herdewijn Piet
Published: September 2008

Dendrimeric‐T and dendrimeric‐A with 36 nucleotides were synthesized using phosphoramidite reagents. These dendrimers contain the nucleosides dA and dT, which are the components of the dA‐dT base pair. Branching was obtained using a bifurcated and trifurcated reagent. The dendrimers were purified by ion‐exchange chromatography. No specific interactions between these dendrimers were observed using atomic force microscopy. However, the dendrimeric‐T is able to disrupt monolayers of fatty acids, resulting in a reorientation of the lipids (from head‐to‐tail to head‐to‐head) as demonstrated by scanning tunneling microscopy (STM).
Capnellenes from the Soft Coral Dendronephthya rubeola
Authors: Grote Daniela , Hänel Frank , Dahse Hans‐Martin , Seifert Karlheinz
Published: September 2008

Four new acetoxycapnellenes 1–4, the first epoxyprecapnellene 5, along with the known dihydroxycapnellene 6 and monoacetoxycapnellene 7, have been isolated from the soft coral Dendronephthya rubeola. The structures were determined primarily by NMR spectroscopy. The compounds 6 and 7 showed a good antiproliferative activity against the cell line L‐929 (murine fibroblasts) and a good cytotoxic activity against the HeLa (human cervix carcinoma) cell line. Compound 6 strongly inhibits the interaction of the oncogenic transcription factor Myc with its partner protein Max. Myc/Max‐Interaction inhibitors are therapeutically interesting compounds in oncology.
A Recombination‐Based Model for the Origin and Early Evolution of Genetic Information
Authors: Lehman Niles
Published: September 2008

Recombination is the exchange of groups of subunits between two entities. It is argued here that this process was central to the origin of life, because it allowed for the creation of useful information from a random pool of linear polymers. The length distribution of such a pool could be broadened if these polymers, such as RNA strands, have the capability of interacting and performing a cross‐strand nucleophilic attack of a hydroxy group on a phosphate. Both the formation of stable secondary structures such as stem‐loops and selection for self‐replication can operate to push the equilibrium length distribution of the pool to longer and more catalytically proficient oligomers. There is empirical and theoretical support for these operations. Finally, in a collection of recombining linear oligomers, the advent of short recognition sequences that favor certain interactions over others, the property of a genotypic ‘self’ could develop, which later can shed its collective nature and be subject to Darwinian evolution. This could have given rise to true replicase enzymes, for example.
Alkaloids from the Roots of Zanthoxylum nitidum and Their Antiviral and Antifungal Effects
Authors: Yang Guohong , Chen Daofeng
Published: September 2008

Five alkaloids, 5,6‐dihydro‐6‐methoxynitidine (1), dictamnine (2), γ‐fagarine (3), skimmianine (4), and 5‐methoxydictamnine (5), were isolated from the roots of Zanthoxylum nitidum. Their structures and configurations were elucidated by spectroscopic methods and X‐ray analysis. Compounds 1, 4, and 5 showed in vitro antiviral effect against hepatitis B virus, and compounds 2, 3, and 5 demonstrated marked antimitotic and antifungal activity.
Iridoid and Aromatic Glycosides from Scrophularia ningpoensisHemsl. and Their Inhibition of [Ca2+]i Increase Induced by KCl
Authors: Chen Bin , Liu Yan , Liu Hong‐Wei , Wang Nai‐Li , Yang Bao‐Feng , Yao Xin‐Sheng
Published: September 2008

Bioassay‐guided fractionation of EtOH extract of the roots of Scrophularia ningpoensis Hemsl. resulted in the isolation of three new iridoid glycosides, i.e., 6″‐O‐caffeoylharpagide (1), 6″‐O‐feruloylharpagide (2), and 6″‐O‐β‐glucopyranosylharpagoside (3), and five new aromatic glycosides, i.e., 2‐(3‐hydroxy‐4‐methoxyphenyl)ethyl O‐α‐arabinopyranosyl‐(1→6)‐O‐α‐rhamnopyranosyl‐(1→3)‐O‐β‐glucopyranoside (4), phenyl O‐β‐xylopyranosyl‐(1→6)‐O‐β‐glucopyranoside (5), 3‐methylphenyl O‐β‐xylopyranosyl‐(1→6)‐O‐β‐glucopyranoside (6), 6‐O‐cinnamoyl β‐fructofuranosyl‐(2→1)‐O‐α‐glucopyranosyl‐(6→1)‐O‐α‐glucopyranoside (7), and 6‐O‐feruloyl β‐fructofuranosyl‐(2→1)‐O‐α‐glucopyranosyl‐(6→1)‐O‐α‐glucopyranoside (8), together with four known compounds, i.e., 6″‐O‐α‐D‐galactopyranosyl harpagoside (9), 6″‐O‐(p‐coumaroyl) harpagide (10), harpagoside (11), and angoroside C (12). Activity of the isolated compounds on [Ca2+]i increase induced by KCl was evaluated on rat cardiac myocytes using confocal laser scanning microscopy. Iridoid glycosides 1, 10, and 11, and aromatic glycosides 5 and 6 significantly inhibited the increase of [Ca2+]i induced by KCl at 100 μM.
Sesquiterpene Glucosides from Chloranthus japonicusSieb.
Authors: Kuang Haixue , Xia Yonggang , Yang Bingyou , Wang Qiuhong , Lü Shaowa
Published: September 2008

A new lindenane sesquiterpene glucoside named yinxiancaoside A (1), a new, rare bidesmosidic megastigmane sesquiterpene glucoside named yinxiancaoside B (5), and three known sesquiterpene glucosides, chloranoside A (2), pisumionoside (3), and sarcaglaboside A (4), were isolated from the whole plant of Chloranthus japonicus Sieb. The structures of the new compounds were established by an extensive study of their spectral data, especially 1D‐ and 2D‐NMR. The cytotoxic activity of the isolated compounds against human hepatoma (Hepg‐2), human ovarian carcinoma (OV420), and human breast cancer (MCF‐7) cells was investigated.
Pyridyl Derivatives of Benzaldehyde as Potential Antisickling Agents
Authors: Nnamani Ijeoma N. , Joshi Gajanan S. , Danso‐Danquah Richmond , Abdulmalik Osheiza , Asakura Toshio , Abraham Donald J. , Safo Martin K.
Published: September 2008

Compounds that bind to sickle hemoglobin (Hb S) producing an allosteric shift to the high‐affinity Hb S that does not polymerize are being developed to treat sickle cell anemia (SCA). In this study, three series of pyridyl derivatives of substituted benzaldehydes (Classes I–III) that combine structural features of two previously determined potent antisickling agents, vanillin and pyridoxal, were synthesized. When analyzed with normal human whole blood, the compounds form Schiff‐base adducts with Hb and left shift the oxygen equilibrium curve (OEC) to the more soluble high‐affinity Hb, more than vanillin or pyridoxal. Generally, Class‐I compounds with an aromatic aldehyde located ortho to the pyridyl substituent are the most potent, followed by the Class‐II compounds with the aldehyde at the meta‐position. Class‐III compounds with the aldehyde at the para position show the weakest activity. The structure–activity studies of these pyridyl derivatives of substituted benzaldehydes demonstrate significant allosteric potency that may be useful for treating SCA.
Synthesis and Biological Evaluation of 4β‐[(4‐Substituted)‐1,2,3‐triazol‐1‐yl]podophyllotoxins as Potential Anticancer Agents
Authors: Reddy Pitta Bhaskar , Agrawal Satyam Kumar , Singh Swaran , Bhat Bilal A. , Saxena Ajit K. , Kumar Halmuthur M. Sampath , Qazi Gulam N.
Published: September 2008

A series of novel 4β‐[(4‐substituted)‐1,2,3‐triazol‐1‐yl]podophyllotoxin derivatives were synthesized by employing CuI‐catalyzed click chemistry and evaluated for their anticancer activity against a panel of seven human cancer cell lines (HT‐29, HCT‐15, 502713, HOP‐62, A‐549, MCF‐7, and SF‐295). The compounds9b, 9c, 9e, 9f, and9hshowed significant cytotoxic activities especially against HT‐29, HCT‐15, 502713 cell lines.
Cytotoxicity of New Stilbenoids from Pholidota chinensis and Their Spin‐Labeled Derivatives
Authors: Wu Bin , Qu Haibin , Cheng Yiyu
Published: September 2008

Chemical investigation of the leave and stem of Pholidota chinensis Lindl has resulted in the isolation and characterization of three new stilbenoids. Their structures were established on the basis of spectroscopic evidence. A series of spin‐labeled stilbene derivatives were synthesized. All of the new compounds were tested for cytotoxicity, and the results revealed that most of the spin‐labeled stilbene derivatives showed superior cytotoxicity in vitro.
Peptaibiomics: Towards a Myriad of Bioactive Peptides Containing Cα‐Dialkylamino Acids?
Authors: Degenkolb Thomas , Brückner Hans
Published: September 2008

Fungi are generally regarded as a literally infinite resource of bioactive secondary metabolites displaying remarkable structural diversity. Research on a particular group of linear and cyclic peptide antibiotics comprehensively named peptaibiotics – as result of the abundance of the non‐proteinogenic Cα‐dialkylated α‐amino acids α‐aminoisobutyric acid (Aib) and isovaline (Iva) – has been started 50 years ago. These peptides have gained constantly increasing interest because of their unique bioactivities and conformations. This review, reflecting the history of peptaibiotic research from 1958 to 2008, is focussed on introducing both the structural diversity and natural microheterogeneity of the peptaibiotics, as well as the biodiversity of their fungal producers. Recently introduced state‐of‐the‐art methods for rapid screening and sequencing of peptaibiotics, such as peptaibiomics and intact‐cell MALDI‐TOF mass spectrometry, are discussed. Finally, future prospects in peptaibiotic research are presented. Owing to the ubiquity and biodiversity of the fungal producers in the biosphere, the discovery of a myriad of peptaibiotics within the next decade is predicted.
{[1‐(Arylmethyl)piperidin‐4‐yl]oxy}‐(trifluoromethyl)‐pyridines: Ketanserin Analogues with Insect Growth Regulating Activity
Authors: Cai Ming‐Yi , Li Zhong , Huang Qingchun , Song Gonghua
Published: September 2008

A series of {[1‐(arylmethyl)piperidin‐4‐yl]oxy}‐(trifluoromethyl)‐pyridine derivatives were designed and synthesized on the basis of the ketanserin (1) framework, a prototypic mammalian 5‐HT2A receptor antagonist, and the structure–activity relationship (SAR) was also discussed. The result of the bioassay showed that most of the title compounds inhibited the insect growth and exhibited moderate‐to‐good growth regulating activity against the armyworm Pseudaletia separata Walker. Furthermore, the SAR study revealed that, when the determinant feature, interacting with mammalian 5‐HT2A receptor, was preserved, a simplified ArCH2 group greatly contributed to insect growth inhibitory activities. It was also found that the substituted position of the CF3 group at the pyridine ring played a key role, and that the introduction of 1‐[bis(4‐fluorophenyl)methyl]piperazine, an equivalent of the benzoylpiperidine moiety of ketanserin, resulted in bioactivities similar to those of the title compounds, which were in agreement with the model of ketanserin analogues binding to mammalian 5‐HT2 receptors.
Development of Highly Chemoselective Bulky Zincate Complex, tBu4ZnLi2: Design, Structure, and Practical Applications in Small‐/Macromolecular Synthesis
Authors: Furuyama Taniyuki , Yonehara Mitsuhiro , Arimoto Sho , Kobayashi Minoru , Matsumoto Yotaro , Uchiyama Masanobu
Published: September 2008

We present full details of the unique reactivities of the newly developed dianion‐type bulky zincate, dilithium tetra‐tert‐butylzincate (tBu4ZnLi2). With this reagent, halogen–zinc exchange reaction of variously functionalized haloaromatics and anionic polymerization of N‐isopropylacrylamide (NIPAm)/styrene with excellent chemoselectivity were realized. Halogen–zinc exchange reaction followed by electrophilic trapping with propargyl bromide provided a convenient route to functionalized phenylallenes, particularly those with electrophilic functional groups (such as cyano, amide and halogens). Spectral and computational studies of the structure in the gas and liquid phases indicated extraordinary stabilization of this dianion‐type zincate by its bulky ligands.
Stannylated Polynorbornenes as New Reagents for a Clean Stille Reaction
Authors: Carrera Nora , Gutiérrez Enrique , Benavente Rut , Villavieja M. Mar , Albéniz Ana C. , Espinet Pablo
Published: September 2008

New functionalized polynorbornenes have been obtained in good yields by vinylic copolymerization of norbornene with a (norbornenyl)SnBu2Cl monomer, catalyzed by [Ni(C6F5)2(SbPh3)2]. Subsequent functionalization produces a wide variety of polymers with different SnBu2R groups (R=aryl, vinyl, alkynyl). The polymers can be used as R‐transfer reagents in Stille couplings, thereby providing easy workup and separation of the polymeric tin byproducts from the coupling products. Tin contents of around 0.05 wt % are found in the Stille products. The stannylated polymers can be recycled and reused with good efficiency.
Models of the ox1 State of Methylcoenzyme M Reductase: Where are the Electrons?
Authors: Gonzalez Emmanuel , Ghosh Abhik
Published: September 2008

The nature of the nickel center in the ox1 form of methylcoenzyme M reductase (MCRox1), the enzyme that catalyzes the last step of biological methanogenesis, has long been controversial. A recent pulse electron paramagnetic resonance (EPR) study suggested a NiIII‐thiolate, or equivalently a high‐spin NiII thiyl radical, description. The MCRox1 hyperfine parameters are best interpreted in terms of a Ni d SOMO, although a pure d SOMO does not explain the fact that about 7 % of the spin‐density resides on the sulfur. The key goals of this DFT (PW91) study were to judge whether the NiIII‐thiolate description is chemically sensible and, if so, to provide a detailed molecular orbital (MO) description of MCRox1. An NiIII‐thiolate description was indeed found to be reasonable and was obtained as the ground state for symmetrized (Cs) oxaporphyrin‐, pyriporphyrin‐, and isoporphyrin‐based model complexes, as well as for a more realistic, biomimetic model. The model calculations yielded a number of insights, key among which are the following: 1) Although the SOMO topology may be viewed as d‐like, this MO also has a substantial amount of metal d character, allowing it to overlap with a thiolate σ lone pair, which would otherwise be orthogonal. 2) In one case (isoporphyrin), we were able to exploit the symmetry of the molecule to independently optimize the (d)1 and (d)1 NiIII states, which turned out to be very close in energy. 3) The near‐degeneracy of these two states provides an elegant explanation for the tendency of these two orbitals to hybridize. Admixture of substantial d character into the d‐type SOMO of our most realistic model of MCRox1 results in a small but distinct spin population of about 0.04 on the sulfur, apparently nicely confirming the conclusions derived from the pulse EPR study. Other pure functionals also confirm this picture, although the hybrid functional B3LYP yields a spin‐density profile that is clearly at odds with the EPR study.
Solvent‐Dependent Changes in the Triazolinedione–Alkene Ene Reaction Mechanism
Authors: Vougioukalakis Georgios C. , Roubelakis Manolis M. , Alberti Mariza N. , Orfanopoulos Michael
Published: September 2008

The influence of the solvent on the triazolinedione–alkene ene reaction mechanism has been investigated. Both inter‐ and intramolecular kinetic isotope effects with tetramethylethylenes and 2,2,2‐(trideuterio)methyl‐7‐methyl‐2,6‐octadiene‐[D3]‐1,1,1 provide, for the first time, strong evidence for changes in the mechanism of the reaction on going from non‐protic to polar protic solvents. In non‐protic polar or apolar solvents, an aziridinium imide that equilibrates to an insignificant extent with an open intermediate (a dipolar or a polarized biradical) is formed irreversibly in the first, rate‐determining step of the reaction, which is followed by fast hydrogen abstraction. On the contrary, in polar protic solvents, hydrogen abstraction is rate limiting, allowing the main dipolar intermediate to equilibrate with its open intermediate(s) as well as with the starting reagents.
Stereoconversion of Amino Acids and Peptides in Uryl‐Pendant Binol Schiff Bases
Authors: Park Hyunjung , Nandhakumar Raju , Hong Jooyeon , Ham Sihyun , Chin Jik , Kim Kwan Mook
Published: September 2008

(S)‐2‐Hydroxy‐2′‐(3‐phenyluryl‐benzyl)‐1,1′‐binaphthyl‐3‐carboxaldehyde (1) forms Schiff bases with a wide range of nonderivatized amino acids, including unnatural ones. Multiple hydrogen bonds, including resonance‐assisted ones, fix the whole orientation of the imine and provoke structural rigidity around the imine CN bond. Due to the structural difference and the increase in acidity of the α proton of the amino acid, the imine formed with an L‐amino acid (1–l‐aa) is converted into the imine of the D‐amino acid (1–D‐aa), with a D/L ratio of more than 10 for most amino acids at equilibrium. N‐terminal amino acids in dipeptides are also predominantly epimerized to the D form upon imine formation with 1. Density functional theory calculations show that 1–D‐Ala is more stable than 1–L‐Ala by 1.64 kcal mol−1, a value that is in qualitative agreement with the experimental result. Deuterium exchange of the α proton of alanine in the imine form was studied by 1H NMR spectroscopy and the results support a stepwise mechanism in the L‐into‐D conversion rather than a concerted one; that is, deprotonation and protonation take place in a sequential manner. The deprotonation rate of L‐Ala is approximately 16 times faster than that of D‐Ala. The protonation step, however, appears to favor L‐amino acid production, which prevents a much higher predominance of the D form in the imine. Receptor 1 and the predominantly D‐form amino acid can be recovered from the imine by simple extraction under acidic conditions. Hence, 1 is a useful auxiliary to produce D‐amino acids of industrial interest by the conversion of naturally occurring L‐amino acids or relatively easily obtainable racemic amino acids.
Investigation of a Possible Solvent Cage Effect in the Reduction of 4‐Aminocyclohexanone by a Hydroxycyclopentadienyl Ruthenium Hydride
Authors: Åberg Jenny B. , Bäckvall Jan‐E.
Published: September 2008

No solvent cage effect could be found in the reduction of 4‐aminocyclohexanone 3 by Shvo's hydroxycyclopentadienyl ruthenium hydride 2. No preference was observed in the complex formation from trapping by aminoalcohol product 4 over external trapping by aminoketone 3 or by Shvo hydride 2. A solvent cage effect has previously been proposed to support an outer‐sphere mechanism in the reduction of imines by 2; this was based on the observation that there was >90% preference for complexation of the newly formed amine over an external amine. Since alcohols form stronger hydrogen bonds than amines a larger cage effect would be expected in the present study. The lack of a cage effect in the present reduction suggests that the previous results from imine reduction require an additional explanation (other than a solvent cage effect).
L‐Proline Catalyzed Enamination of β‐Dicarbonyl Compounds under Solvent‐free Conditions
Authors: KUNDU Dhiman , MAJEE Adinath , HAJRA Alakananda
Published: September 2008

A simple, general and efficient method has been developed for synthesis of various β‐enamino ketones and esters by reacting β‐dicarbonyl compounds with amines using a catalytic amount of L‐proline at room temperature under solvent‐free conditions in excellent yields.
Supramolecular Assemblies Using Piperazine with Dicarboxylic Acids and Hydroxy‐carboxylic Acids
Authors: CHEN Zi‐Yun , PENG Meng‐Xia
Published: September 2008

The molecular self‐assembly of piperazine (pip) with 1,4‐cyclohexanedicarboxylic acid (H2chda), m‐phthalic acid (H2mpda), 6‐hydroxy‐2‐naphthalic acid (Hohna) and 1‐hydroxy‐2‐naphthalic acid (Hshna) results in four new supramolecular networks formulated as H2pip·chda (1), H2pip·2Hmpda (2), H2pip·ohna·2H2O (3) and H2pip·shna (4), respectively. Single‐crystal X‐ray diffraction study reveals that compounds 1–3 are three‐dimensional supramolecular networks, while 4 has a one‐dimensional hydrogen‐bonded chain‐based structure, with CCDC: 672051 (1), 672052 (2), 672053 (3) and 672054 (4).
Low Temperature Heat Capacities and Thermodynamic Properties of 2‐Methyl‐2‐butanol
Authors: TONG Bo , TAN Zhi‐Cheng , WANG Shao‐Xu
Published: September 2008

The low‐temperature heat capacity Cp,m of 2‐methyl‐2‐butanol was precisely measured in the temperature range from 80 to 305 K by means of a small sample automated adiabatic calorimeter. Three solid‐solid phase transitions and one solid‐liquid phase transition were found at T=146.355, 149.929, 214.395 and 262.706 K from the experimental Cp‐T curve, respectively. The dependence of heat capacity on temperature was fitted to the following polynomial equations with a least square method. In the temperature range of 80 to 140 K, Cp,m=39.208+8.0724X−1.9583X2+10.06X3+1.799X4−7.2778X5+1.4919X6, X= (T−110)/30; in the temperature range of 155 to 210 K, Cp,m=70.701+10.631X+12.767X2+0.3583X3−22.272X4−0.417X5+12.055X6, X= (T−182.5)/27.5; in the temperature range of 220 to 250 K, Cp,m=99.176+7.7199X−26.138X2+28.949X3+0.7599X4−25.823X5+21.131X6, X= (T−235)/15; and in the temperature range of 270 to 305 K, Cp,m=121.73+16.53X−1.0732X2−34.937X3−19.865X4+24.324X5+18.544X6, X= (T−287.5)/17.5. The molar enthalpies of these transitions were determined to be 0.9392, 1.541, 0.6646 and 2.239 kJ·mol−1, respectively. The molar entropies of these transitions were determined to be 6.417, 10.28, 3.100 and 8.527 J·K−1·mol−1, respectively. The thermodynamic functions [HT−H298.15] and[ST−S298.15], were derived from the heat capacity data in the temperature range of 80 to 305 K with an interval of 5 K.
Stabilities and Spectroscopy of Hydrogen Bonding Complexes Formed by 2,4‐Bis(acrylamido)pyrimidines
Authors: ZHANG Ye , LI Ting , TENG Qi‐Wen
Published: September 2008

Hydrogen bonds play important roles to living organisms containing pyrimidine‐based derivatives. The electronic structures of the hydrogen bonding complexes formed by 2,4‐bis(acrylamido)pyrimidine (2,4‐BAAP) derivatives with 1‐substituted uracil were studied using Austin Model 1 (AM1) and density function theory (DFT) methods. The UV and NMR spectra of the complexes were calculated with the INDO/CIS (configuration interaction for singlet in intermediate neglect of differential overlap) and B3LYP/6‐31G(d) methods. It was shown that the complexes could be formed via the triple hydrogen bonding between two monomers owing to the negative binding energies. The binding energies of the complexes were weakened in the presence of substituents, but this weakening effect depended on the simultaneous influence of the electronic and steric effects. The binding energies of the complexes were also decreased owing to the formation of the isomeric complexes in the presence of piperidyl on 2,4‐BAAP. The energy gaps of the complexes were lessened in the presence of electron‐donating groups. Holes and electrons were easily injected to the complexes due to the extension of the conjugation chain. The first UV absorptions of the complexes relative to those of the parent compound were red‐shifted because of the narrow energy gaps. The chemical shifts of the carbon atoms on the CO bonds in the complexes were changed downfield.
Microcalorimetric Study on the Inhibition of Escherichia coli by Some Novel Pyridine Amide Schiff Base Derivatives
Authors: LI Chao‐Hong , ZHANG Li‐Xia , CAI Li‐Hua , LIU Yi , HU Pei‐Zhi
Published: September 2008

The antibacterial effect of a series of novel pyridine amide Schiff base compounds on Escherichia coli was investigated by a microcalorimetric method at 37 °C. The metabolic power‐time curves of the bacteria treated by the compounds were obtained, and the thermokinetic parameters were analyzed, from which the antibacterial activities of these compounds were evaluated. The results show that two compounds F and G have good activity on aerobic multiplying metabolism of E. coli, with the value of IC50 106 and 113 mg/L respectively, but have no effective action on the fermentation metabolism of E. coli. The action of the compounds on the non‐multiplying metabolism was investigated by taking the heat output of E. coli in the stationary phase as the guideline of the activity. The experimental results revealed that the hydrophilicity of these Schiff bases had a great influence on their antibacterial activity, which results from the bacterial cell wall structure. The antibacterial structure‐activity relationship of these Schiff base derivatives was also briefly discussed. The antibacterial activity of the compounds against E. coli was as follows: compound F>G>C>D>E>B>A.
Electrochemical and Photoelectrochemical Study of Self‐assembled Monolayer of Phytic Acid on Brass
Authors: XU Qun‐Jie , WAN Zong‐Yue , ZHOU Guo‐Ding , YIN Ren‐He , CAO Wei‐Min , LIN Chang‐Jian
Published: September 2008

Phytic acid is an environment‐friendly reagent for processing metals. The anticorrosion and inhibiting mechanism for phytic acid monolayers self‐assembled on a brass (HSn70‐1) electrode has been investigated by using electrochemical and photocurrent response methods. The electrochemical measurements indicate that phytic acid is liable to form surface complexes on the brass electrode, and the self‐assembled monolayers (SAM) change the structure of the electric double‐layer and shift the potential of zero charge positively. The photochemical measurement indicates that the brass electrode shows a p‐type photoresponse owing to the formation of a Cu2O layer on its surface, and the presence of SAM weakens significantly the photoresponse, suggesting an excellent effect on anticorrosion, which is consistent with the EIS and polarization curve measurements. Adsorption of phytic acid was found to be typical of chemisorption, which can be reasonably described on the basis of the Langmuir isotherm.
Interactions of Ovalbumin with Ionic Surfactants
Authors: GUO Xia , YAN Hui , GUO Rong
Published: September 2008

The interactions of ovalbumin (OVA) with one anionic surfactant, sodium dodecyl sulfate (SDS), and two cationic surfactants, dodecyl trimethylammonium bromide (DTAB) and cetyl trimethylammonium bromide (CTAB), in water have been studied through fluorescence and UV‐Vis spectroscopies and transmission electronic microscopy, combined with the measurement of conductivity. OVA can increase the critical micelle concentrations (cmc) of SDS and CTAB but has little effect on that of DTAB. The interaction between surfactant monomer and OVA is greater than that between surfactant micelles and OVA. Moreover, SDS can make OVA unfolded while cationic surfactants cannot.
New Features on the Phase Transitions of Behenic Acid Monolayers as Unveiled by 2D‐Compressibility Coefficient
Authors: GAO Wen‐Ying , YU Zhi‐Wu
Published: September 2008

Phase behavior of Langmuir monolayers of behenic acid (BeA) has been examined by two‐dimensional compressibility. It was found that phase transitions of BeA could be classified into two distinct categories, named Type‐I and Type‐II in this work. The former is typified by a positive peak on the compressibility‐pressure (β‐) curve, indicating the transition can occur itself in a way of collapse from the initial structure. The latter is characterized by a dropping step on the β‐ curve, implying that it cannot happen itself and the driven force is continuous compression. For BeA molecules, compressibility coefficients at the initial and final state are the same, βi=βf, for Type‐I phase transition from L2 to L2' state, whilst βi>βf for Type‐II phase transition from L2' state to S state.
Synthesis, Crystal Structure and Electrochemical Studies of Two Novel Zn(II) Complexes of Phthalic Acid and Imidazole Derivatives
Authors: LI Wei‐Hua , ZHAO Guang‐Fa , HUANG Zhao‐Ge , LIU Fa‐Qian , DING Nai‐Xiu , LIU Guang‐Ye
Published: September 2008

Two novel coordination polymers [Zn(pa)(vim)2]n (1) and [Zn(pa)(eim)2]n (2) (pa=phthalic acid dianion, vim=1‐vinyl‐1H‐imidazole, eim=1‐ethyl‐1H‐imidazole) have been synthesized and their structures characterized by X‐ray single crystal diffractometry and elemental analysis. Both of the complexes consist of [Zn(L)2] (L=vim for 1; eim for 2) entities linked into polymeric zigzag chains along the crystallographic c‐axis by bridging phthalate anions in the µ2‐1,2 coordination mode. The coordination around each Zn(II) atom is tetrahedral. There are only van der Waals interactions between the chains in 1, while the three‐dimensional network in 2 is assembled by CH···O contacts. The electrochemical studies reveal that redoxes of Zn2+/Zn in complexes 1 and 2 are irreversible processes.
Determination of Glucose by Affinity Adsorption Solid Substrate‐room Temperature Phosphorimetry Based on Triticum Vulgare Lectin Labeled with Silicon Dioxide Nanoparticle Containing Fluorescein Isothiocyanate
Authors: LIU Jia‐Ming , LIU hen‐Bo , LI Zhi‐Ming , HE Hang‐Xia , LIN Wei‐Nü , HUANG Ya‐Hong , WANG Fang‐Mei
Published: September 2008

In the presence of heavy atom perturber Pb2+, silicon dioxide nanoparticle containing fluorescein isothiocyanate (FITC‐SiO2) could emit a strong and stable room temperature phosphorescence (RTP) signal on the surface of acetyl cellulose membrane (ACM). It was found in the research that a quantitative specific affinity adsorption (AA) reaction between triticum vulgare lectin (WGA) labeled with luminescent nanoparticle and glucose (G) could be carried on the surface of ACM. The product (WGA‐G‐WGA‐FITC‐SiO2) of the reaction could emit a stronger RTP signal, and the ΔIp had linear correlation to the content of G. According to the facts above, a new method to determine G by affinity adsorption solid substrate room temperature phosphorimetry (AA‐SS‐RTP) was established, based on WGA labeled with FITC‐SiO2. The detection limit (LD) of this method calculated by 3Sb/k was 0.47 pg·spot−1 (corresponding to a concentration value 1.2×10−9 g·mL−1, namely 5.3×10−9 mol·L−1), the sensitivity was high. Meanwhile, the mechanism for the determination of G by AA‐SS‐RTP was discussed.
Synthesis of Natural α ‐6‐Dehydroxy‐6‐aminoglucoglycerolipids
Authors: WU Hai‐Jun , LI Chun‐Xia , SONG Gao‐Peng , LI Ying‐Xia
Published: September 2008

Two natural 6‐dehydroxy‐6‐aminoglucoglycerolipids were first synthesized in a convenient approach. The key step was the selective α‐glycosylation of 6‐dehydroxy‐2,3,4‐tri‐O‐benzyl‐6‐amino‐D‐glucopyranosyl trichloroacetimidate donor 10 with (S)‐isopropyleneglycerol using diethyl ether as glycosylation solvent to give 3‐O‐(2,3,4‐tri‐O‐benzyl‐6‐dehydroxy‐6‐benzyloxycarbonylamino‐α‐D‐glucopyranoyl)‐1,2‐O‐isopropylene‐sn‐glycerol 7. Removal of acetonide group of 7 and acylation with various fatty acids, then deprotection of benzyl and Cbz groups and selective acylation of the amino group afforded the marine natural glycoglycerolopids of sn‐1,2‐dipalmitoyl‐3‐(N‐palmitoyl‐6‐dehydroxy‐6‐amino‐α‐glucosyl)glycerol 3 and sn‐1‐palmitoyl‐2‐myristoyl‐3‐(N‐stearoyl‐6‐dehydroxy‐6‐amino‐α‐glucosyl)glycerol 4. The structures of the synthetic samples were identified by 1H, 13C NMR, and HRESIMS.
Microwave‐accelerated Synthesis of Some (±)‐1‐Aryl‐5‐chloroisochromans
Authors: SAEED Aamer , MUMTAZ Amara
Published: September 2008

Solventless one‐pot synthesis of some new (±)‐1‐aryl‐5‐chloroisochromans by cyclocondensation of 2‐(2‐chlorophenyl)ethanol with aromatic aldehydes via an acid catalyzed oxa‐Pictet‐Spengler reaction under microwave irradiation is described.
Electrochemical Synthesis of 5‐Purin‐6'‐ylthiocatechols in Aqueous Medium
Authors: LIU Fu‐Jian , ZENG Cheng‐Chu , PING Da‐Wei , CAI Yuan‐Li , ZHONG Ru‐Gang
Published: September 2008

The electrochemical synthesis of 5‐purin‐6′‐ylthiocatechols was carried out by anodic oxidation of catechol derivatives 1a–1d in the presence of 6‐mercaptopurine (2) in aqueous solution. Results of cyclic voltammetry and controlled‐potential electrolysis indicated that the starting catechols were first oxidized to the corresponding o‐benzoquinone, which underwent further Michael addition with 6‐mercaptopurine to produce titled products 3a–3d following an EC (E=electrochemical and C=chemical step) mechanism. Such work further demonstrates the versatility of the anodic oxidation of catechols and their in‐situ transformation for the synthesis of derivatized catechols.
Asymmetric Hydrogenation of α‐Hydroxy Ketones: A Reaction Sensitive toward Electronic Effect of Substrates
Authors: XU Hui , MENG Qing‐Hua , ZHANG Zhao‐Guo
Published: September 2008

An efficient asymmetric hydrogenation of α‐hydroxy ketones was reported with the catalyst prepared from [RuCl2(benzene)]2 and SunPhos, chiral terminal 1,2‐diols were obtained in up to 99% ee. This Ru‐catalyzed asymmetric hydrogenation reaction of α‐hydroxy ketones represents a new route for the synthesis of chiral terminal 1,2‐diols.
Chiral Separation of Novel α ‐Aminophosphonates Containing a Benzothiazole Moiety by Liquid Chromatography Using an Amylose Stationary Phase
Authors: LU Ping , ZHANG Yu‐Ping , SONG Bao‐An , YANG Song , BHADURY Shankar Pinaki , HU De‐Yu , XUE Wei , CHEN Zhuo , JIN Lin‐Hong
Published: September 2008

The present report describes a chiral HPLC method for the enantiomeric separation of α‐aminophosphonate derivatives using two new coated and immobilized amylose‐based chiral stationary phases (CSP, Chiralpak IA and Chiralpak AD‐H). The chromatographic parameters such as retention factor (k), separation factor (α), and resolution (Rs) of the solutes were investigated on these two CSPs. Reasonably good baseline separation for these compounds was achieved using Chiralpak IA column. The influences of temperature, content of ethanol modifier and the structure of analyte were also studied. THF, EtOAc and CH2Cl2 were used as eluents on analytical and semi‐preparative columns. Highly enriched enantiomers with purities of up to 96.4% –100% (ee) and yields of 90.2% –95.5% were obtained, respectively. The proposed methods were found to be suitable and accurate for rapid separation and semi‐preparation of enantiomeric α‐aminophosphonate derivatives available.
New Transition and Actinide Metal Complexes of 2‐Carboxy‐phenylhydrazo‐Benzoylacetone Ligand: Synthesis, Characterization and Biological Study
Authors: KHALIL M. M. H. , MASHALY M. M.
Published: September 2008

A new series of binary mononuclear complexes were prepared from the reaction of the hydrazone ligand, 2‐carboxyphenylhydrazo‐benzoylacetone (H2L), with the metal ions, Cd(II), Cu(II), Ni(II), Co(II), Th(IV) and UO2(VI). The binary Cu(II) complex of H2L was reacted with the ligands 1,10‐phenanthroline or 2‐aminopyridine to form mixed‐ligand complexes. The binary complexes of Cu(II) and Ni(II) are suggested to have octahedral configurations. The Cd(II) and Co(II) complexes are suggested to have tetrahedral and/or square‐planar geometries, respectively. The Th(IV) and UO2(VI) complexes are suggested to have octahedral and dodecahedral geometries, respectively. The mixed‐ligand complexes have octahedral configurations. The structures of all complexes and the corresponding thermal products were elucidated by elemental analyses, conductance, IR and electronic absorption spectra, magnetic moments, 1H NMR and TG‐DSC measurements as well as by mass spectroscopy. The ligand and some of the metal complexes were found to activate the enzyme pectinlyase.
Heterogeneous Palladium Chloride Catalyzed Ligand‐free Suzuki‐Miyaura Coupling Reactions at Ambient Temperature
Authors: WANG Min , WANG Lei
Published: September 2008

A mild and efficient ligand‐free Suzuki‐Miyaura coupling reaction catalyzed by heterogeneous palladium chloride was developed at room temperature in a short reaction time under air atmosphere. Various phenyl iodides, bromides and activated chlorides were coupled with sodium tetraphenylborate or phenylboronic acids efficiently to afford the corresponding cross‐coupled products in good to excellent yields. Furthermore, the catalyst could be recycled up to four times without loss of its activity.
Theoretical and Experimental Studies of the Inclusion Phenomena of β‐Cyclodextrin with Organic Amines
Authors: SONG Le‐Xin , WANG Hai‐Ming , TENG Chuan‐Feng , BAI Lei , XU Peng , GUO Xue‐Qing
Published: September 2008

The inclusion complexations of β‐cyclodextrin (β‐CD) with ethylenediamine 1 and its three analogs, diethylenetriamine 2, triethylamine 3 and ethylene diaminetetraacetic acid 4 were examined by means of both experimental measurements and theoretical calculations. From the polarimetric method, it was found that β‐CD could form 1/1 host‐guest inclusion complexes with these guests, and the formation constants (K) of the inclusion complexes have also been determined in aqueous solution at 298.2 K. Semiempirical PM3 calculations were carried out to assess the intermolecular binding ability of β‐CD to a series of short chain aliphatic amines such as guests 1–7, cyclic aliphatic amines 8–11, and aromatic amines 12–13. The interaction processes between β‐CD and the guests were reported, and the complexation differences of β‐CD with these guests also discussed. The energy contribution from deformation energy or hydrate energy to interaction energy in the inclusion systems was found to be quite small. The stability of β‐CD inclusion complexes depended on the size fit between the host and guest. For β‐CD complexes of guests 1–4, the order of the K values from the polarimetric measurements is in good accordance with that of the absolute values of the complexation energies from PM3 calculations.
Palladium Immobilized on Silica Gel: A Novel and Reusable Catalyst for Heck Reaction
Authors: WANG Zu‐Li , WANG Lei , YAN Jin‐Can
Published: September 2008

The immobilization of palladium on silica gel in Heck reaction has been developed. Iodobenzenes, bromobenzenes and activated chlorobenzenes were coupled with olefins (Heck reaction) smoothly to afford the corresponding cross‐coupling products in good to excellent yields under phosphine‐ and amine‐free reaction conditions in the presence of silica gel supported palladium, Silica‐Ap‐Pd cat. as catalyst, potassium carbonate as base and DMF as solvent. Furthermore, the silica‐supported palladium catalyst 3 could be recovered and recycled by a simple filtration of the reaction solution and used for 6 consecutive trials without significant loss of its catalytic activity.
Synthesis and Antibacterial Activity of Some New 2,5‐Disubstituted‐1,3,4‐oxadiazole Derivatives
Authors: SOMANI Rakesh R. , SHIRODKAR Prabhakar Y. , KADAM Vilasrao J.
Published: September 2008

Synthesis of some new oxadiazole derivatives starting from 1,2,3‐benzo[d]triazole‐1‐acetic hydrazide (1) is described. The target compounds 2‐(N‐substituted‐aminocarbonylmethylthio)‐5‐(1,2,3‐benzo[d]triazol‐1‐ylmethyl)‐ 1,3,4‐oxadiazole (4a–4i) and 2‐[2‐(N‐substituted‐aminocarbonyl)ethylthio]‐5‐(1,2,3‐benzo[d]triazol‐1‐ylmethyl)‐ 1,3,4‐oxadiazole (5a–5i) were obtained in good yields via cyclisation of 1 and subjected to antibacterial activity test against pathogenic bacteria. The halogen containing mono‐ and di‐substituted derivatives showed excellent antibacterial activity compared to other analogues.
Histologic associations and long‐term cancer risk in columnar cell lesions of the breast
Authors: Boulos Fouad I. , Dupont William D. , Simpson Jean F. , Schuyler Peggy A. , Sanders Melinda E. , Freudenthal Marcia E. , Page David L.
Published: September 2008

BACKGROUND.

Mammary columnar cell lesions with atypia have been receiving increased scrutiny in view of their association with atypical hyperplasia (AH) and carcinoma. However, the few retrospective outcome studies performed have failed to establish an increased risk for recurrence or carcinoma on long‐term follow‐up.

METHODS.

The authors evaluated the overall cancer risk for 1261 biopsies with columnar cell lesions (CCL) in 4569 women from the Nashville Breast Cohort who were biopsied between 1969 and 1988. On the basis of Schnitt and Vincent‐Salomon's classification, they also classified 229 biopsies with CCL into 3 categories: without hyperplasia or atypia, with hyperplasia lacking atypia, and with atypia. By using a nested case‐control design, they compared the risks of invasive cancer associated with these 3 categories.

RESULTS.

A 2‐ to 3‐fold increase in the occurrence of AH in the presence of CCL versus in their absence (P < .005) was observed. Relative risk of invasive breast cancer for women with both AH and CCL compared with those with AH alone did not differ significantly (risk ratio [RR] = 1.55; P = .29). The presence of CCL alone was associated with a mild increase in the overall cancer risk (RR = 1.47; P = .05). In the nested case‐control study, no significant risk difference was observed among the 3 categories of CCL.

CONCLUSIONS.

The authors observed a positive association between CCL and AH. The possibility that CCL by themselves significantly elevate breast cancer risk is not well supported. However, a finding of CCL on benign breast biopsy may indicate the presence of AH, a more worrisome lesion. Cancer 2008. © 2008 American Cancer Society.