bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of 3‐Aminotropones from N‐Boc‐Protected Furan‐2‐amine (=tert‐Butyl Furan‐2‐ylcarbamate; Boc=(tert‐Butoxy)carbonyl) by Cycloaddition Reactions and Subsequent Rearrangement
Authors: Montaña Ángel M. , Barcia Juan A. , Kociok‐Köhn Gabriele , Font‐Bardia Mercè , Solans Xavier 
Published: February 2008

AbstractThe 3‐aminotropones (=3‐aminocyclohepta‐2,4,6‐trien‐1‐ones) 4 were prepared in two steps by i) a [4+3] cycloaddition reaction between a conveniently substituted α,α′‐dihalo ketone 1 and a furan‐2‐amine derivative 2 functionalized at C(2) by a protected amino group (→3), and ii) a base‐induced molecular rearrangement of the cycloadduct 3 via cleavage of the O‐bridge. A mechanism for the formation of 3‐aminotropones is proposed on the basis of the initial deprotonation of the [(tert‐butoxy)carbonyl]amino (BocNH) group of 3, followed by O‐bridge opening, an acid–base equilibrium, and finally an alkoxyaluminate elimination to afford the conjugated stable troponoid system (Scheme 7).
Selenium‐Containing Heterocycles from Isoselenocyanates: 4‐Methylselenazole Derivatives from the Reaction with Malononitrile and Propargyl Chloride
Authors: Sommen Geoffroy L. , Linden Anthony , Heimgartner Heinz 
Published: February 2008

AbstractAryl isoselenocyanates 1 react with malononitrile (6a) and propargyl chloride (8) in DMF in the presence of Et3N to give the corresponding 2‐(3‐aryl‐2,3‐dihydro‐4‐methyl‐1,3‐selenazol‐2‐ylidene)malononitriles 12 as major products. The analogous reaction takes place with benzoylacetonitrile (6f) instead of 6a. In some cases, the corresponding noncyclic 2‐[(arylamino)(prop‐2‐ynylselanyl)methylidene]malononitriles 9 were obtained as minor products. The structures of 9e and 11a have been established by X‐ray crystallography.
Heteroclitins N – Q, New Compounds from Stems of Kadsura heteroclita (Roxb.) Craib
Authors: Xu Li‐Jia , Liu Hai‐Tao , Peng Yong , Chen Si‐Bao , Chen Shi‐Lin , Xiao Pei‐Gen 
Published: February 2008

AbstractFrom the stems of Kadsura heteroclita (Roxb.) Craib, a new novel C19 homolignan, heteroclitin N (1), as well as three new lignans, heteroclitins OQ (2–4), were isolated. Their structures were elucidated based on spectral analysis, including 1D and 2D NMR experiments. There is an additional spirocyclic oxirane system in heteroclitin O (2), which is the first example of a lignan with an oxirane ring in a spirobenzofuranoid dibenzocyclooctene structure in the genus Kadsura.
Synthesis of Optically Active 1‐(1‐Phenylethyl)‐1H‐imidazoles Derived from 1‐Phenylethylamine
Authors: Mlostoń Grzegorz , Mucha Paulina , Urbaniak Katarzyna , Broda Karolina , Heimgartner Heinz 
Published: February 2008

AbstractThe three‐component reaction of (R)‐ or (S)‐1‐phenylethylamine (6), formaldehyde, and an α‐(hydroxyimino) ketone 5, i.e., 3‐(hydroxyimino)butan‐2‐one (5a) or 2‐(hydroxyimino)‐1,2‐diphenylethanone (5b), yields the corresponding enantiomerically pure 1‐(1‐phenylethyl)‐1H‐imidazole 3‐oxide 7 in high yield (Schemes 2 and 3). The reactions are carried out either in MeOH or in AcOH. Smooth transformations of the N‐oxides into optically active 1‐(1‐phenylethyl)‐1H‐imidazoles 10 and 2,3‐dihydro‐1‐(1‐phenylethyl)‐1H‐imidazole‐2‐thiones 11 are achieved by treatment of 7 with Raney‐Ni and 2,2,4,4‐tetramethyl‐3‐thioxocyclobutanone (12), respectively (Scheme 4).
Three New Monoterpenoid Indole Alkaloids from Ervatamia flabelliformis
Authors: Liang Shuang , Chen Hai‐Sheng , Shen Yun‐Heng , Zhang Wei‐Dong , Jin Yong‐Sheng , Liu Run‐Hui 
Published: February 2008

AbstractThe three new monoterpenoid indole alkaloids 1–3 were isolated from the stems of Ervatamia flabelliformis. The structures were elucidated on the basis of spectral analysis and chemical derivatization.
A Novel Route to 1‐Substituted 3‐(Dialkylamino)‐9‐oxo‐9H‐indeno[2,1‐c]pyridine‐4‐carbonitriles
Authors: Landmesser Thomas , Linden Anthony , Hansen Hans‐Jürgen 
Published: February 2008

AbstractHeptalenecarbaldehydes 1/1′ as well as aromatic aldehydes react with 3‐(dicyanomethylidene)‐indan‐1‐one in boiling EtOH and in the presence of secondary amines to yield 3‐(dialkylamino)‐1,2‐dihydro‐9‐oxo‐9H‐indeno[2,1‐c]pyridine‐4‐carbonitriles (Schemes 2 and 4, and Fig. 1). The 1,2‐dihydro forms can be dehydrogenated easily with KMnO4 in acetone at 0° (Scheme 3) or chloranil (=2,3,5,6‐tetrachlorocyclohexa‐2,5‐diene‐1,4‐dione) in a ‘one‐pot’ reaction in dioxane at ambient temperature (Table 1). The structures of the indeno[2,1‐c]pyridine‐4‐carbonitriles 5′ and 6a have been verified by X‐ray crystal‐structure analyses (Fig. 2 and 4). The inherent merocyanine system of the dihydro forms results in a broad absorption band in the range of 515–530 nm in their UV/VIS spectra (Table 2 and Fig. 3). The dehydrogenated compounds 5, 5′, and 7a–7f exhibit their longest‐wavelength absorption maximum at ca. 380 nm (Table 2). In contrast to 5 and 5′, 7a–7f in solution exhibit a blue‐green fluorescence with emission bands at around 460 and 480 nm (Table 4 and Fig. 5).
Total Synthesis of the Alkaloid (±)‐Aspidophytine Based on Carbonyl Ylide Cycloaddition Chemistry
Authors: Mejía‐Oneto José M. , Padwa Albert 
Published: February 2008

AbstractThe RhII‐catalyzed cycloaddition cascade of an indolyl‐substituted α‐diazo imide was used for the total synthesis of the complex pentacyclic alkaloid (±)‐aspidophytine. Treatment of the resulting dipolar cycloadduct with BF3⋅OEt2 induces a domino fragmentation cascade. The reaction proceeds by an initial cleavage of the oxabicyclic ring and formation of a transient N‐acyl iminium ion which reacts further with the adjacent tert‐butyl ester and sets the required lactone ring present in aspidophytine. A three‐step sequence was then used to remove both the ester and OH groups. Subsequent functional group manipulations allowed for the high‐yielding conversion to (±)‐aspidophytine.
Three New Pteridines, Hirudinoidines A – C, from Hirudo nipponicaWhitman
Authors: Li You‐Bin , Huang Wei‐Hua , Xiang Yu 
Published: February 2008

AbstractThree new pteridines, hirudinoidines A – C (1–3, resp.), with novel structural features were isolated from Hirudo nipponica Whitman, and their structures were elucidated on the basis of extensive spectroscopic analyses and by comparison of their spectral data with those of related metabolites. The configuration of 1 was unequivocally confirmed by single‐crystal X‐ray diffraction (Fig. 2).
Pyrrolizidine Alkaloids and Bisabolane Sesquiterpenes from the Roots of Ligularia cymbulifera
Authors: Liu Chun‐Mei , Wang He‐Xiang , Wei Shi‐Lei , Gao Kun 
Published: February 2008

AbstractThe new pyrrolizidine alkaloid glycoside 1, and the three new highly oxygenated bisabolane sesquiterpenes 4–6, together with the two known pyrrolizidine alkaloids 2 and 3, were isolated from the roots of Ligularia cymbulifera (W. W. Smith) Hand.‐Mazz. Their structures were established on the basis of spectroscopic analysis, especially 1D‐ and 2D‐NMR data. The cytotoxic activities of compounds 1, 2, and 4–6 were evaluated against hepatoma (BEL‐7402), human leukemia (HL‐60), human ovarian carcinoma (HO‐8910), and nasopharyngeal carcinoma (KB) cell lines (Tables 1–3). Compound 6 showed weak cell‐growth inhibition of BEL‐7402 cell.
Pteridines. Part CXIX.
Authors: Pfleiderer Wolfgang 
Published: February 2008

AbstractA variety of pyrimidine precursors 12–25 were converted into a series of new 7‐hydroxylumazines (=7‐hydroxypteridine‐2,4(1H,3H)‐diones) 26–35 which functioned as starting materials for the transformation into the corresponding 7‐chlorolumazines 36–45. Subsequent reaction with hydrazine led to the 7‐hydrazinolumazines 46–55 which gave on nitrosation the 7‐azidolumazines 1 and 56–64. These compounds were subjected to short heating in xylene whereby 1 and 56–61 showed a new pteridine–purine interconversion in forming a new type of 1,3‐disubstituted or 3‐substituted xanthin‐8‐amine‐derived nitrilium ylides (2,3,6,7‐tetrahydro‐N‐methylidyne‐2,6‐dioxo‐1H‐purin‐8‐aminium ylides) 11 and 65–70. The presence of an additional 6‐alkyl substituent in the 7‐azidolumazines 63 and 64 or of an unsubstituted N(3) position in 62 caused further rearrangement to xanthine‐9‐carbonitriles 71–73. Prolonged heating of 7‐azido‐1,3‐dimethyllumazine (1) also afforded theophylline‐9‐carbonitrile (=1,2,3,6‐tetrahydro‐1,3‐dimethyl‐2,6‐dioxo‐9H‐purine‐9‐carbonitrile; 5). The nitrilium ylide function was established by NMR and UV spectra as well as by elemental analyses. Confirmation of the nitrilium ylide structures was suggested by the result of the heating of 1,3‐dimethyl‐N‐methylidynexanthin‐8‐aminium ylide 11 in EtOH or of 1 in pentan‐1‐ol leading to 8‐aminotheophylline (=8‐amino‐3,7‐dihydro‐1,3‐dimethyl‐1H‐purin‐2,6‐dione; 74).
Hydrological response to timber harvest in northern Idaho: implications for channel scour and persistence of salmonids
Authors: Tonina Daniele , Luce Charles H. , Rieman Bruce , Buffington John M. , Goodwin Peter , Clayton Stephen R. , Alì Shawkat Md. , Barry Jeffrey J. , Berenbrock Charles 
Published: February 2008

AbstractThe potential for forest harvest to increase snowmelt rates in maritime snow climates is well recognized. However, questions still exist about the magnitude of peak flow increases in basins larger than 10 km2 and the geomorphic and biological consequences of these changes. In this study, we used observations from two nearly adjacent small basins (13 and 30 km2) in the Coeur d'Alene River basin, one with recent, relatively extensive, timber harvest, and the other with little disturbance in the last 50 years to explore changes in peak flows due to timber harvest and their potential effects on fish. Peak discharge was computed for a specific rain‐on‐snow event using a series of physical models that linked predicted values of snowmelt input to a runoff‐routing model. Predictions indicate that timber harvest caused a 25% increase in the peak flow of the modelled event and increased the frequency of events of this magnitude from a 9‐year recurrence interval to a 3·6‐year event. These changes in hydrologic regime, with larger discharges at shorter recurrence intervals, are predicted to increase the depth and frequency of streambed scour, causing up to 15% added mortality of bull trout (Salvelinus confluentus) embryos. Mortality from increased scour, although not catastrophic, may have contributed to the extirpation of this species from the Coeur d'Alene basin, given the widespread timber harvest that occurred in this region. Copyright © 2008 John Wiley & Sons, Ltd.
Chemical respiratory allergy and occupational asthma: what are the key areas of uncertainty?
Authors: Isola Daniel , Kimber Ian , Sarlo Katherine , Lalko Jon , Sipes I. Glenn 
Published: February 2008

AbstractThere is increasing concern about the association of respiratory disease with indoor air quality and environmental atmospheric pollution. Associated with this is the fact that in many countries there has been a significant increase in the prevalence of asthma. Against this background there is a need to address the toxicological, occupational and public health problems associated with the ability of some chemicals to cause allergic sensitization of the respiratory tract and occupational asthma.By definition allergic sensitization of the respiratory tract to chemicals is dependent upon the stimulation of an adaptive immune response that leads to development of respiratory allergy and/or asthma. Although IgE antibody is associated typically with respiratory sensitization to protein allergens, there is less certainty about the role played by antibodies of this type in chemical respiratory allergy and occupational asthma. There are currently no validated or widely accepted methods/models for the identification and characterization of chemicals that have the potential to induce allergic sensitization of the respiratory tract.These and other areas of uncertainty were debated during the course of and following a two day Workshop. The primary purpose of the Workshop was to consider the important clinical and toxicological issues associated with chemical respiratory allergy, and to identify key questions that need to be answered if real progress is to be made. Copyright © 2008 John Wiley & Sons, Ltd.
Viper metalloproteinase (Agkistrodon halys pallas) with antimicrobial activity against multi‐drug resistant human pathogens
Authors: Samy Ramar Perumal , Gopalakrishnakone Ponnampalam , Chow Vincent T.K. , Ho Bow 
Published: February 2008

AbstractMetalloproteinases are abundant enzymes in crotalidae and viperidae snake venoms. Snake venom metalloproteinases (SVMPs) comprise a family of zinc‐dependent enzymes, which display many different biological activities. A 23.1 kDa protein was isolated from Agkistrodon halys (pallas, Chinese viper) snake venom. The toxin is a single chain polypeptide with a molecular weight of 23146.61 and an N‐terminal sequence (MIQVLLVTICLAVFPYQGSSIILES) relatively similar to that of other metalloprotein‐like proteases isolated from the snake venoms of the Viperidae family. The antibacterial effect of Agkistrodon halys metalloproteinase (AHM) on Burkholderia pseudomallei (strains TES and KHW), Escherichia coli, Enterobacter aerogenes, Proteus vulgaris, Proteus mirabilis, Pseudomonas aeruginosa (Gram‐negative bacteria) and Staphylococcus aureus (Gram‐positive bacterium) was studied at a concentration 120 µM. Interestingly, we found that the metalloproteinase exhibited antibacterial properties and was more active against S. aureus, P. vulgaris, P. mirabilis and multi‐drug resistant B. pseudomallei (strain KHW) bacteria. AHM variants with high bacteriostatic activity (MIC 1.875–60 µM) also tended to be less cytotoxic against U‐937 human monocytic cells up to 1 mM concentrations. These results suggest that this metalloprotein exerts its antimicrobial effect by altering membrane packing and inhibiting mechanosensitive targets. J. Cell. Physiol. 216: 54–68, 2008. © 2008 Wiley‐Liss, Inc.
TNF‐α represses connexin43 expression in hacat keratinocytes via activation of JNK signaling
Authors: Tacheau Chalotte , Laboureau Julien , Mauviel Alain , Verrecchia Franck 
Published: February 2008

AbstractWe used both pharmacological and gene knockout approaches to elucidate the specific roles played by the Jun‐N‐terminal kinase (JNK) and NFκB pathways downstream of TNF‐α in the context of connexin43 (Cx43) gene expression. We demonstrate that TNF‐α reduces the expression of Cx43 in HaCat cell lines at the protein and mRNA levels, and transcriptionally. We also demonstrate that TNF‐α decreases gap junctional intercellular communication (GJIC) between HaCat cells. Using pharmacological inhibitors of the NFκB signaling pathway, we determined that the NFκB signaling cascade is not implicated in TNF‐α effect on Cx43 expression and in the subsequent decrease of GJIC. Conversely, in NFκB essential modulator (NEMO−) fibroblasts, lack of NFκB activation did not influence both the effect of TNF‐α on Cx43 expression and on GJIC. In contrast, pharmacologic inhibition of JNK abolishes TNF‐α‐driven repression of Cx43 gene expression and GJIC between HaCat cells. Using JNK‐JNK (JNK−/−) fibroblasts, we demonstrate that similar regulatory mechanisms take place in fibroblasts. Together, these results identify JNK and not NFκB, as a critical mediator of TNF‐α repressory effect on Cx43 gene expression. J. Cell. Physiol. 216: 438–444, 2008. © 2008 Wiley‐Liss, Inc.
In vivo MR imaging of hippocampal lesions in multiple sclerosis
Authors: Roosendaal Stefan D. , Moraal Bastiaan , Vrenken Hugo , Castelijns Jonas A. , Pouwels Petra J.W. , Barkhof Frederik , Geurts Jeroen J.G. 
Published: February 2008

AbstractPurposeTo investigate whether a recently improved version of the three‐dimensional double inversion‐recovery (3D‐DIR) technique enables the in vivo detection of hippocampal lesions in multiple sclerosis (MS).Materials and MethodsMagnetic resonance images of 16 patients and nine healthy control subjects were acquired at 1.5T. Lesions were scored on 3D‐DIR images and were anatomically classified as white matter (WM), cortical, or hippocampal lesions. Associations between hippocampal, cortical, and WM lesion numbers were evaluated. Also, hippocampal lesions were retrospectively assessed on 3D‐T2 and hippocampal and brain volumes were measured.ResultsNo hippocampal lesions were detected in control subjects. By contrast, 14 out of 16 MS patients had at least one hippocampal lesion. The mean number (±SD) of hippocampal lesions detected with 3D‐DIR was 2.6 ± 1.8 in MS patients; only 56% of these lesions could be observed on 3D‐T2.ConclusionHippocampal lesions can be visualized in vivo with 3D‐DIR and occur frequently in MS. The ability to visualize hippocampal lesions in vivo is of fundamental importance to future studies focusing on the role of gray matter (GM) damage in cognitive deficits, which are common in MS. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.
A fast navigator‐gated 3D sequence for delayed enhancement MRI of the myocardium: Comparison with breathhold 2D imaging
Authors: Nguyen Thanh D. , Spincemaille Pascal , Weinsaft Jonathan W. , Ho Bernard Y. , Cham Matthew D. , Prince Martin R. , Wang Yi 
Published: February 2008

AbstractPurposeTo develop a rapid navigator‐gated three‐dimensional (3DNAV) delayed‐enhancement MRI (DE‐MRI) sequence for myocardial viability assessment, and to evaluate its performance with breathhold two‐dimensional (2DBH) DE‐MRI sequence as the reference standard.Materials and Methods2DBH DE‐MRI was initiated 10 minutes after contrast administration and followed by 3DNAV DE‐MRI in 23 patients at 1.5 T. Comparison was performed using three qualitative criteria (image quality score, diagnostic outcome, relative diagnostic confidence score) in all patients, and three quantitative criteria (infarct volume, infarct signal‐to‐noise ratio [SNRinf], and infarct‐viable myocardium contrast‐to‐noise ratio [CNRinf‐myo]) in patients with hyperenhanced myocardium.ResultsCompared to 2DBH DE‐MRI, 3DNAV DE‐MRI provided slightly better image quality, the same final diagnostic outcomes, and better relative diagnostic confidence score with 79% SNRinf improvement (P = 0.002) and 90% CNRinf‐myo improvement (P = 0.004) in 39% less scan time (414 ± 118 seconds for 2DBH and 251 ± 93 seconds for 3DNAV). The measured infarct volumes demonstrated excellent correlation (18.9 ± 19.0 mL for 2DBH DE‐MRI vs. 17.6 ± 19.0 mL for 3DNAV DE‐MRI, r2 = 0.998, P < 0.001, N = 7) and narrow limits of agreement (–1.3 ± 1.8 mL).Conclusion3DNAV DE‐MRI provides improved image quality and similar infarct detection in less scan time compared to the standard 2DBH DE‐MRI. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.
Time‐resolved contrast‐enhanced MR angiography of intracranial lesions
Authors: Zou Zhitong , Ma Lin , Cheng Liuquan , Cai Youquan , Meng Xianghui 
Published: February 2008

AbstractPurposeTo determine if contrast‐enhanced (CE) MRI of intracranial lesions benefits from time‐resolved MR angiography (MRA) during contrast agent injection.Materials and MethodsFor 126 patients with suspected intracranial lesions undergoing routine CE MRI at 3.0T (N = 88) or 1.5T (N = 38), time‐resolved CE MRA (three‐dimensional [3D] time‐resolved imaging of contrast kinetics [TRICKS]) was performed during injection of the routine gadolinium (Gd) dose of 0.1 mmol/kg. Time to peak (TTP) enhancement of lesions as well as time to internal carotid artery (ICA), middle cerebral artery (MCA), superior sagittal sinus (SSS), and jugular vein enhancement were measured. Source and maximum intensity projection (MIP) images were reviewed to delineate the spatial relationship of lesions and the vasculature.ResultsIn 61 patients (48%), additional important findings were detected on time‐resolved MRA that were not seen on the routine CE protocol, including aneurysms (N = 6), arteriovenous malformations (N = 7), ICA stenoses (N = 2), vascular anomalies (N = 18), and relationships between lesions and vessels (N = 28). In addition, tumor TTP correlated with glioma grade (r = 0.87) and discriminated epithelial from nonepithelial meningiomas (P = 2.6 × 10–5). MRA added eight minutes to the total exam time.ConclusionTime‐resolved MRA performed during contrast agent injection adds information to the routine brain CE MRI examination of intracranial lesions with only a small time penalty and no additional risk to the patient. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.
Whole‐brain functional magnetic resonance imaging mapping of acute nociceptive responses induced by formalin in rats using atlas registration‐based event‐related analysis
Authors: Shih Yen‐Yu I. , Chen You‐Yin , Chen Chiao‐Chi V. , Chen Jyh‐Cheng , Chang Chen , Jaw Fu‐Shan 
Published: February 2008

AbstractNociceptive neuronal activation in subcortical regions has not been well investigated in functional magnetic resonance imaging (fMRI) studies. The present report aimed to use the blood oxygenation level‐dependent (BOLD) fMRI technique to map nociceptive responses in both subcortical and cortical regions by employing a refined data processing method, the atlas registration‐based event‐related (ARBER) analysis technique. During fMRI acquisition, 5% formalin (50 μl) was injected into the left hindpaw to induce nociception. ARBER was then used to normalize the data among rats, and images were analyzed using automatic selection of the atlas‐based region of interest. It was found that formalin‐induced nociceptive processing increased BOLD signals in both cortical and subcortical regions. The cortical activation was distributed over the cingulate, motor, somatosensory, insular, and visual cortices, and the subcortical activation involved the caudate putamen, hippocampus, periaqueductal gray, superior colliculus, thalamus, and hypothalamus. With the aid of ARBER, the present study revealed a detailed activation pattern that possibly indicated the recruitment of various parts of the nociceptive system. The results also demonstrated the utilization of ARBER in establishing an fMRI‐based whole‐brain nociceptive map. The formalin induced nociceptive images may serve as a template of central nociceptive responses, which can facilitate the future use of fMRI in evaluation of new drugs and preclinical therapies for pain. © 2008 Wiley‐Liss, Inc.
A call for longitudinal research in positive organizational behavior
Authors: Avey James B. , Luthans Fred , Mhatre Ketan H. 
Published: February 2008

AbstractAfter defining and providing the current status of psychological capital (PsyCap), we address the need to better understand its stability (i.e., state vs. trait). Specifically, we issue a call for longitudinal research. The balance of this “incubator” article examines the relevance, potential obstacles, and advantages of this design in meeting PsyCap's future research needs. Copyright © 2008 John Wiley & Sons, Ltd.