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  • 2000-2004  (434)
  • 1955-1959  (5,457)
  • 1890-1899  (10,434)
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  • Inorganic Chemistry  (11,178)
  • General Chemistry  (5,087)
  • gene expression
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  • 1
    Electronic Resource
    Electronic Resource
    Preservation of Gene Expression Ratios Among Multiple Complex cDNAs After PCR Amplification: Application to Differential Gene Expression Studies (2000)
    Springer
    Journal of structural and functional genomics 1 (2000), S. 1-7 
    Details
    ISSN: 1570-0267
    Keywords: cDNA ; PCR cDNA ; TaqMan Analysis ; gene expression ; Pearson's correlation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Comparative gene expression studies are often limited by low availability of tissue and poor quality of extractable mRNA. Collective PCR amplification of minute quantities of mRNA has great potential for overcoming these limitations. However, there remains significant concern about the effects of amplification on the absolute and relative abundance of individual mRNAs that could complicate subsequent gene expression studies. To address this problem, we systematically compared the relative abundance of many specific mRNAs from complex cDNA preparations (from tissue and cultured cells) both before and after amplification by PCR. Our results demonstrated that, as expected, the absolute abundance of different mRNAs in a cDNA library is altered in an unpredictable manner by PCR amplification. However, we found that the concentration ratios of specific mRNAs among different cDNA preparations were routinely well conserved after PCR amplification. Thus, for the purpose of comparative expression studies for specific mRNAs in two (or more) complex cDNAs, PCR-amplified cDNA is equally useful as unamplified cDNA. These results provide a rigorous experimental validation and offer a theoretical treatment to support the utility of PCR amplified cDNA for differential gene expression studies. We conclude that the inherent difficulties in performing differential screening studies such as gene chip and array analyses on limited amounts of biological materials can be overcome by a PCR amplification step without compromising data quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011337409258
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  • 2
    Electronic Resource
    Electronic Resource
    The interferon-α regulation of interferon regulatory factor 1 (IRF-1) and IRF-2 has therapeutic implications in carcinoid tumors (2000)
    Springer
    Annals of oncology 11 (2000), S. 707-714 
    Details
    ISSN: 1569-8041
    Keywords: gene expression ; IRF-1 and IRF-2 ; p68 ; PKR ; signal transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background:Interferon regulatory factor 1 (IRF-1) has beendemonstrated to possess antiproliferative and tumor suppressor functions, onthe contrary, IRF-2 has been suggested to induce oncogenetic effect in somecell lines, but not evaluated in tumor patients. Patients and methods:In 35 carcinoid tumor patients, expressionsof IRF-1 and IRF-2 were investigated by immunohistochemistry and their valueswere analyzed with clinical treatment response. In carcinoid tumor cell line,Bon1, effects of IFN-α on the expression of both IRF-1 and IRF-2 mRNAs andproteins were determined by Northern blot, RNase protection assays and Westernblot analysis. Results:IFN-α up-regulated the expression of IRF-1 and IRF-2both in vivoand in vitro. In carcinoid tumors, IFN-αtreatment led to a significant increase in the expression of IRF-1 (P〈 0.001) and IRF-2 (P 〈 0.001). Moreover, the IRFs inductionwas correlated with the clinical response of IFN-α treatment, althoughtheir baseline values were not predictive. In addition, expressions of IRF-1and IRF-2 were significantly correlated with the p68kinaseexpression (P = 0.032 and P = 0.0176, respectively) and theexpression of IRF-1 protein was positively correlated with that of IRF-2(r = 0.671,P = 0.0001) tested in the same specimens. Conclusions:IRF-1 as well as IRF-2 have therapeutic implicationsin carcinoid tumors during treatment with interferon-α and IRFs inductionmight be used as indicators of response to treatment with interferon-α.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008314804492
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  • 3
    Electronic Resource
    Electronic Resource
    Expression of Four Genes of Bacteriophage MB78 from Contiguous Open Reading Frames: The Genomic Organization as Deduced by Sequence Analysis (2000)
    Springer
    Virus genes 20 (2000), S. 87-97 
    Details
    ISSN: 1572-994X
    Keywords: bacteriophage MB78 ; contiguous ORF ; unusual start codons ; genome analysis ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Four proteins of bacteriophage MB78 having apparent molecular weights as 35, 14, 21 and 16 kDa are expressed from 3.9 kb SalI-HindIII fragment located almost in the middle of the phage genome. Analysis of the sequence supported by some experimental evidences suggest that these four proteins are expressed from polycistronic message without any intercistronic gap. Stop and start codons of consecutive ORFs overlap and rare initiation codons are used. Computer analysis of the sequence suggests the presence of two more open reading frames within the ORFs of 35 and 16 kDa proteins but in the opposite orientation, i.e. in the complementary strand.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008168425571
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  • 4
    Electronic Resource
    Electronic Resource
    Pollen Embryogenesis - The Stress Mediated Switch from Gametophytic to Sporophytic Development. Current Status and Future Prospects (2000)
    Springer
    Biologia plantarum 43 (2000), S. 481-489 
    Details
    ISSN: 1573-8264
    Keywords: cell symmetry ; gene expression ; heat shock proteins ; polarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Embryogenesis can be initiated directly from microspores or pollen grains. This is known as androgenesis and refers to the process of redirection of normal pollen development (gametophytic pathway) towards the embryo formation (sporophytic). This review mainly deals with the current knowledge of stress and developmental aspects of induction of androgenesis. The crucial role of stress inductive treatment together with changes in cell polarity are discussed in relation to other relevant biological systems. The intriguing speculations are made on the basis of these comparisons which may point out the direction of future investigations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1002835330799
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of Peptide Lys-Glu on Interleukin-2 Gene Expression in Lymphocytes (2000)
    Springer
    Bulletin of experimental biology and medicine 130 (2000), S. 898-899 
    Details
    ISSN: 1573-8221
    Keywords: peptides ; gene expression ; interleukin-2 ; lymphocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Lys-Glu in vitro stimulated interleukin-2 gene expression in mouse spleen lymphocytes. This effect depended on peptide concentration and duration of treatment. It is hypothesized that this peptide is the shortest regulatory fragment promoting the transport of trans-acting factors into the nucleus. It can not be excluded that Lys-Glu is a structural component of trans-acting factor active centers, which are necessary for the activation of interleukin-2 gene transcription in lymphocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015382732640
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  • 6
    Electronic Resource
    Electronic Resource
    Regulation of Functional Activity of Bone Marrow Hemopoietic Stem Cells by Erythroid Cells in Mice (2000)
    Springer
    Bulletin of experimental biology and medicine 130 (2000), S. 1159-1161 
    Details
    ISSN: 1573-8221
    Keywords: erythroblasts ; cytokines ; gene expression ; hemopoietic stem cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Transplantation of erythroid and bone marrow cells to irradiated mice stimulated exogenous colony formation. Pretreatment of erythroid cells with specific rabbit antiserum to erythroblasts abolished this effect. The reverse transcriptase polymerase chain reaction revealed the presence of mRNA for interleukin-1α, interleukin-1β, interleukin-3, interleukin-6, and granulocyte-macrophage colony-stimulating factor in erythroid cells. Granulocyte-macrophage colony-stimulating factor was found in the conditioned medium from erythroid cells. Thus, erythroid cells stimulated colony-forming activity of bone marrow cells, which was probably mediated via cytokine synthesis (e.g., granulocyte-macrophage colony-stimulating factor).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017523800090
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  • 7
    Electronic Resource
    Electronic Resource
    Dexamethasone induced cardiac hypertrophy in newborn rats is accompanied by changes in myosin heavy chain phenotype and gene transcription (2000)
    Springer
    Molecular and cellular biochemistry 209 (2000), S. 165-174 
    Details
    ISSN: 1573-4919
    Keywords: myosin heavy chain ; gene expression ; hypertrophy ; dexamethasone ; promoter function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Cardiac hypertrophy has been observed in newborn infants treated with dexamethasone (DEX). This study was undertaken to examine whether DEX-induced hypertrophy in newborn rats is associated with redistribution of cardiac myosin heavy chain (MHC) isoforms and if so, the effects involve transcriptional regulation. Newborn rats were injected with either DEX (1 mg/kg/day; s.c.) or equivalent volume normal saline for 1, 3, 5, 7 or 9 days. Hypertrophy was quantified by heart dry/wet wt ratios, heart/body wt ratios, and total protein content of the myocardium. Changes in the expression of cardiac MHC mRNA were characterized by northern blot and slot blot analyses, using isoform specific probes for a- and β-MHC genes. DEX effect on α-MHC gene transcription was analyzed by transiently transfecting various α-MHC promoter/CAT reporter constructs into primary cultures of cardiac myocytes derived from one day old rat pups. DEX administration into newborn rats produced significant cardiac hypertrophy ranging from 23% at day 1 to 59% at 9 days. The hypertrophy was accompanied by immediate increase (83%) in steady state level of the α-MHC mRNA within one day and a maximum increase (148%) at 7 days of treatment. The steady state level of β-MHC mRNA declined by 25% at day 1 and a maximum decrease of 54% at day 7 of DEX treatment. The changes in MHC mRNA were also reflected in their protein levels as determined by V1 and V3 isozyme analysis. DEX treatment of primary cultures of cardiomyocytes following transfection with a-MHC promoter/CAT reporter constructs resulted in increased CAT expression in a dose dependent manner. The minimum α-MHC gene sequences responding to DEX treatment were located between the -200 to -74-bp region of the gene, resulting in 2-fold and 6-fold activation of CAT reporter after 0.05 and 0.1 mM doses of DEX, respectively. Our data indicate that DEX induced cardiac hypertrophy in newborn rats is accompanied by increased expression of α-MHC and decreased expression of β-MHC. The α-MHC effects are mediated in part through transcriptional mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007128300430
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  • 8
    Electronic Resource
    Electronic Resource
    The effect of thioacetamide on the activity and expression of cytosolic rat liver glutathione-S-transferase (2000)
    Springer
    Molecular and cellular biochemistry 211 (2000), S. 103-110 
    Details
    ISSN: 1573-4919
    Keywords: thioacetamide ; glutathione-S-transferase ; rat liver ; transcription ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of thioacetamide (TA), an hepatotoxic and hepatocarcinogenic compound, on the expression and activity of the cytosolic enzyme glutathione-S-transferase (GST) was studied in rat liver. Four h following the administration of 14C-labeled thioacetamide (10 mg/Kg), several subunits of GST were found to be radioactively labeled. A single sublethal dose of TA (250 mg/Kg) decreased by three-fold the expression of classα GST at 24-48 h of treatment, but did not significantly affect the transcription of class μ GST. The activity of the enzyme toward 1-chloro-2,4-dinitrobenzene was mildly inhibited (66% of the control) by a 24 h TA treatment and gradually increased thereafter. It is proposed that the covalent binding of TA or its derivative to the GST subunits does not affect the activity of the enzyme. Nevertheless, GST activity inhibition is due to the deleterious effect of TA on GST transcription.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007114801362
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  • 9
    Electronic Resource
    Electronic Resource
    Control of cardiomyocyte gene expression as drug target (2000)
    Springer
    Molecular and cellular biochemistry 212 (2000), S. 135-142 
    Details
    ISSN: 1573-4919
    Keywords: gene expression ; catecholamines ; angiotensin II ; heart failure ; myosin ; hypertension ; eprosartan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Pressure overload of the heart is associated with a perturbed gene expression of the cardiomyocyte leading to an impaired pump function. The ensuing neuro-endocrine activation results in disordered influences of angiotensin II and catecholamines on gene expression. To assess whether angiotensin II type 1 receptor inhibition can also counteract a raised sympathetic nervous system activity, spontaneously hypertensive rats fed a hypercaloric diet were treated with eprosartan (daily 90 mg/kg body wt) and cardiovascular parameters were monitored with implanted radiotelemetry pressure transducers. Both, blood pressure and heart rate were increased (p 〈 0.05) by the hypercaloric diet. Although eprosartan reduced (p 〈 0.05) the raised systolic and diastolic blood pressure, the diet-induced rise in heart rate was blunted only partially. In addition to drugs interfering with the enhanced catecholamine influence, compounds should be considered that selectively affect cardiomyocyte gene expression via 'metabolic' signals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007181626766
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  • 10
    Electronic Resource
    Electronic Resource
    Transcriptional regulation of cyclooxygenase-2 in the Human Microvascular Endothelial Cell Line, HMEC-1: Control by the combinatorial actions of AP2, NF-IL-6 and CRE elements (2000)
    Springer
    Molecular and cellular biochemistry 203 (2000), S. 41-51 
    Details
    ISSN: 1573-4919
    Keywords: prostaglandin ; cyclooxygenase ; transcriptional regulation ; gene expression ; promotor activation ; transcription ; endothelial cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Interleukin-1β (IL-1) is a potent inducer of cyclooxygenase-2 (COX-2) and prostaglandin biosynthesis in many types of cells, yet little is known about the molecular mechanisms regulating IL-1 mediated prostanoid biosynthesis in the endothelium of the microvasculature. Therefore, we examined the cis- and trans-acting factors regulating IL-1-induced COX-2 expression in the human microvascular endothelial cell line, HMEC-1. IL-1 enhanced steady state levels of COX-2 protein and mRNA synthesis by ≈ 2-fold which preceded a 2-fold increase in PGFα biosynthesis. Expression of a series of COX-2 promoter-luciferase constructs in IL-1 treated HMEC-1 cells revealed that the 'full length' (-1432/+59 bp) promoter was 10 times more active than the SV-40 promoter/enhancer and that it could be further activated by IL-1. Surprisingly however, all except for the shortest COX-2 promoter construct retained the ability to respond to IL-1 and luciferase activity driven by -191/+59 bp COX-2 promoter was as responsive to IL-1 as the full-length promoter. Moreover, site-directed promoter mutagenesis and electophoretic mobility shift assays (EMSA) indicate that the combinatorial actions of AP2, NF-IL6, and CRE elements are critical for both constitutive and IL-1-inducible COX-2 promoter activity. Understanding the mechanism(s) regulating COX-2 gene expression and prostaglandin biosynthesis in the microvasculature has important implications with regard to inflammation and angiogenesis in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007045600664
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  • 11
    Electronic Resource
    Electronic Resource
    Characterization of a 5′-flanking region supporting the transcription of mouse thymosin β-4 in mouse NIH3T3 cells (2000)
    Springer
    Molecular and cellular biochemistry 203 (2000), S. 163-167 
    Details
    ISSN: 1573-4919
    Keywords: thymosin β-4 ; gene expression ; chloramphenicol acetyltransferase ; NIH3T3 cells ; interferon response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Expression of the gene coding for thymosin β-4 (Tβ-4), the major G-actin sequestering peptide in the cell, is regulated mainly at the level of transcription. In this study, we examined the nucleotide sequence of the 5′-flanking region (from - 2202 to - 881) of the mouse Tβ-4 gene, and demonstrated that the DNA fragment from -278 to +410 of this gene was capable of directing the expression of a chloramphenicol acetyltransferase reporter gene in NIH3T3 cells. However, expression of the reporter gene in cells cannot be induced by interferon-a treatment even though a rapid activation of endogenous Tβ-4 gene by this cytokine was observed. These results suggest that the projected interferon-stimulated response element (ISRE) might reside in other parts of the mouse Tβ-4 gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007020619788
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  • 12
    Electronic Resource
    Electronic Resource
    Upstream regulatory elements in chick heme oxygenase-1 promoter: A study in primary cultures of chick embryo liver cells (2000)
    Springer
    Molecular and cellular biochemistry 209 (2000), S. 17-27 
    Details
    ISSN: 1573-4919
    Keywords: AP-1 ; cobalt chloride ; gene expression ; heme oxygenase ; oxidative stress ; sodium arsenite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Previously, chick heme oxygenase-1 (cHO-1) gene was cloned by us and two regions important for induction by sodium arsenite were identified. These two regions were found to contain consensus sequences of an AP-1 (-1580 to -1573) and a MRE/cMyc complex (-52 to -41). In the current study, the roles of these two elements in mediating the sodium arsenite or cobalt chloride dependent induction of cHO-1 were investigated further. DNA binding studies and site-directed mutagenesis studies indicated that both the AP-1 and MRE/cMyc elements are important for the sodium arsenite induction, while cobalt chloride induction involves only the AP-1 element. Electrophoretic mobility shift assays showed that nuclear proteins binding to the AP-1 element was increased by both sodium arsenite or cobalt chloride treatment, whereas the binding of proteins to the MRE/cMyc element showed a high basal expression in untreated cells and the binding activity was only slightly increased by sodium arsenite treatment. Site-directed mutagenesis studies showed that, to completely abolish sodium arsenite induction, both the AP-1 and MRE/cMyc elements must be mutated; mutation of either element alone resulted in only a partial effect. In contrast, a single mutation at AP-1 element was sufficient to reduce the cobalt chloride induction almost completely. The MRE/cMyc complex plays a major role in the basal level expression, and shares some similarities to the upstream stimulatory factor element (USF) identified in the promoter regions of mammalian HO-1 genes and other stress regulated genes. Because sodium arsenite is known to cause oxidative stress and because activation of AP-1 proteins has been shown to be a key step in the oxidative stress response pathway, we also explored the possibility that the induction of the cHO-1 gene by sodium arsenite is mediated through oxidative stress pathway(s) by activation of AP-1 proteins. We found that pretreatment with antioxidants (N-acetyl cysteine or quercetin) reduced the induction of the endogenous cHO-1 message or cHO-1 reporter construct activities induced by sodium arsenite or cobalt chloride. These antioxidants also reduced the protein binding activities to the AP-1 element in the electrophoretic mobility shift assays. In summary, induction of the cHO-1 gene by sodium arsenite or cobalt chloride is mediated by activation of the AP-1 element located at -1,573 to -1,580 of the 5′ UTR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007025505842
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  • 13
    Electronic Resource
    Electronic Resource
    CRE-decoy oligonucleotide-inhibition of gene expression and tumor growth (2000)
    Springer
    Molecular and cellular biochemistry 212 (2000), S. 29-34 
    Details
    ISSN: 1573-4919
    Keywords: cAMP ; transcription factor-decoy oligonucleotides ; CRE ; Ap-1 ; p53 ; tumor growth ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Nucleic acid molecules with high affinities for a target transcription factor can be introduced into cells as decoy cis-elements to bind these factors and alter gene expression. This review discusses a synthetic single-stranded palindromic oligonucleotide, which self-hybridizes to form a duplex/hairpin and competes with cAMP response element (CRE) enhancers for binding transcription factors. This oligonucleotide inhibits CRE- and Ap-1-directed gene transcription and promotes growth inhibition in vitro and in vivo in a broad spectrum of cancer cells, without adversely affecting normal cell growth. Evidence presented here suggests that the CRE-decoy oligonucleotide can provide a powerful new means of combating cancers, viral diseases, and other pathological conditions by regulating the expression of cAMP-responsive genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007144618589
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  • 14
    Electronic Resource
    Electronic Resource
    Catecholamines and angiotensinogen gene expression in kidney proximal tubular cells (2000)
    Springer
    Molecular and cellular biochemistry 212 (2000), S. 73-79 
    Details
    ISSN: 1573-4919
    Keywords: adrenergic receptors ; renin-angiotensin system (RAS) ; gene expression ; kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract To investigate the molecular mechanism(s) of action of catecholamines on the expression of the angiotensinogen (ANG) gene in kidney proximal tubular cells, we used opossum kidney (OK) cells with a fusion gene containing the 5′-flanking regulatory sequence of the rat ANG gene fused with a human growth hormone (hGH) gene as a reporter, pOGH (rANG N-1498/+18), permanently integrated into their genomes. The level of expression of the ANG-GH fusion gene was quantified by the amount of immunoreactive-hGH (IR-hGH) secreted into the medium. The addition of norepinephrine (NE), isoproterenol (a β1/β2-adrenergic receptor (AR) agonist) and iodoclonidine (an α2-AR agonist) stimulated the expression of the ANG-GH fusion gene in a dose-dependent manner, whereas the addition of epinephrine and phenylephrine (α1-AR agonist) had no effect. The stimulatory effect of NE was blocked by the presence of propranolol (β-AR blocker), atenolol (β1-AR blocker), yohimbine (α2-AR blocker), Rp-cAMP (an inhibitor of cAMP-dependent protein kinase AI & AII) and staurosporine (an inhibitor of protein kinase C), but was not blocked by ICI 118, 551 (β2-AR blocker) and prazosin (α1-AR blocker). The addition of a combination of isoproterenol and iodoclonidine or a combination of 8-Bromo-cAMP (8-Br-cAMP) and phorbol 12-myristate (PMA) synergistically stimulated the expression of the ANG-GH fusion gene as compared to the addition of isoproterenol, iodoclonidine, 8-Br-cAMP or PMA alone. Furthermore, the addition of NE, 8-Br-cAMP or PMA stimulated the expression of pOGH (rANG N-806/-779/-53/+18), a fusion gene containing the putative cAMP responsive element (CRE, ANG N-806/-779) upstream of the ANG promoter (ANG N-53/+18) in OK cells, but had no effect on the expression of fusion genes containing the mutant of the CRE. Gel mobility shift assays revealed that the ANG-CRE binds with the DNA-binding domain (bZIP 254-327) of the cAMP-responsive binding protein (CREB). The binding of the labeled ANG-CRE to CREB (bZIP254-327) was displaced by unlabeled ANG-CRE and the CRE of the somatostatin gene but not by the mutants of the ANG-CRE. Finally, NE stimulated the phosphorylation of CREB in OK cells. These studies demonstrate that the molecular mechanism(s) of NE action on the expression of the ANG gene in OK cells may be mediated via both the PKA and PKC signalling pathways and via the phosphorylation of CREB. The phosphorylated CREB then interacts with the CRE in the 5′-flanking region of the ANG gene and subsequently stimulates the gene expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007152821315
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  • 15
    Electronic Resource
    Electronic Resource
    Expression of renin-angiotensin system and extracellular matrix genes in cardiovascular cells and its regulation through AT1 receptor (2000)
    Springer
    Molecular and cellular biochemistry 212 (2000), S. 203-209 
    Details
    ISSN: 1573-4919
    Keywords: angiotensinogen ; fibronectin ; gene expression ; transcriptional regulation ; cardiomyocytes ; vascular smooth muscle cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Angiotensinogen (AGT) is a unique substrate of the renin-angiotensin system and fibronectin (FN) is an important component of the extracellular matrix. These play critical roles in the pathophysiological changes including cardiovascular remodeling and hypertrophy in response to hypertension. This study was performed to examine the regulation of AGT and FN gene in cardiac myocytes (CMs) and vascular smooth muscle cells (VSMCs) in response to mechanical stretch. Mechanical stretch significantly increased the AGT mRNA expression in CMs, while these stimuli did not affect FN mRNA levels. On the other hand, Mechanical stretch upregulated FN mRNA levels in VSMCs, whereas no increase in AGT mRNA levels was observed in response to stretch stimuli. An angiotensin II type 1 (AT1) receptor antagonist (CV11974) significantly decreased these stretch-mediated increases in mRNA level and promoter activity of the AGT and FN gene, whereas angiotensin II type 2 (AT2) receptor antagonist (PD123319) did not affect the induction. These results indicate that mechanical stretch activates transcription of the AGT and FN gene mainly via AT1 receptor-pathway in CMs and VSMCs. Furthermore, mechanisms regulating AGT and FN gene seem to be different between CMs and VSMCs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007141912654
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  • 16
    Electronic Resource
    Electronic Resource
    Regulation of angiotensin II receptors in the medullary thick ascending limb (2000)
    Springer
    Molecular and cellular biochemistry 212 (2000), S. 211-217 
    Details
    ISSN: 1573-4919
    Keywords: angiotensin receptor ; medullary thick ascending limb ; sodium intake ; primary cell culture ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Angiotensin II (Ang II) is an important regulator of the function of medullary thick ascending limb of loop of Henle (MTAL). Recent studies showed that changes in Ang II receptor expression occur and underlie changes in the function of proximal tubules during altered sodium intake. The present experiment was designed to determine (1) whether expression of the type 1 Ang II (AT1) receptor in the MTAL is regulated by altered sodium intake, and (2) the specific pathway(s) mediating sodium-induced AT1 expression in the MTAL. Wistar rats were fed a normal sodium (0.5%, NS), low sodium (0.07%, LS), or high sodium (4%, HS) diet for 2 weeks. Northern blot analysis and radioligand binding showed that in rats fed a normal sodium diet the rank of order for both AT1 mRNA expression and receptor density was outer medulla 〉 cortex 〉 inner medulla. Sodium restriction significantly increased both AT1 mRNA expression and receptor density in the outer medulla. In contrast, neither AT1 mRNA expression nor receptor density in the outer medulla was altered by sodium loading. Losartan treatment (3 mg/kg/per day by oral gavage for 2 weeks) prevented low sodium-induced upregulation of the AT1 receptor in the outer medulla, but it had no effect on AT1 expression in the outer medulla of rats fed a normal sodium diet. Highly purified suspensions of MTAL were isolated from rats fed a normal or low sodium diet. Low sodium intake significantly increased AT1 mRNA level by 184% and AT1 receptor density by 58% in MTALs. Primary cultures of MTAL cells were treated with PBS, Ang II (10-8 M), and Ang II + 17 octadecynoic (17 ODYA, 10 μM). Ang II caused about 2-fold increase in AT1 mRNA levels, and this increase was diminished by about 30% by the addition of 17 ODYA. We conclude that (1) sodium restriction but not sodium loading increases AT1 receptor expression in the MTAL, (2) low sodium-induced upregulation of the AT1 receptor in the MTAL is Ang II-dependent, and (3) Ang II-induced upregulation of the AT1 receptor in the MTAL is mediated, at least in part, by cytochrome P450 pathways.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007193931309
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  • 17
    Electronic Resource
    Electronic Resource
    Role of cardiac renin-angiotensin system in sarcoplasmic reticulum function and gene expression in the ischemic-reperfused heart (2000)
    Springer
    Molecular and cellular biochemistry 212 (2000), S. 227-235 
    Details
    ISSN: 1573-4919
    Keywords: renin angiotensin system ; sarcoplasmic reticulum ; Ca2+-handling ; gene expression ; ischemia-reperfusion ; cardioprotection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The aim of this study was to explore the possible participation of cardiac renin-angiotensin system (RAS) in the ischemia-reperfusion induced changes in heart function as well as Ca2+-handling activities and gene expression of cardiac sarcoplasmic reticulum (SR) proteins. The isolated rat hearts, treated for 10 min without and with 30 μM captopril or 100 μM losartan, were subjected to 30 min ischemia followed by reperfusion for 60 min and processed for the measurement of SR function and gene expression. Attenuated recovery of the left ventricular developed pressure (LVDP) upon reperfusion of the ischemic heart was accompanied by a marked reduction in SR Ca2+-pump ATPase, Ca2+-uptake and Ca2+-release activities. Northern blot analysis revealed that mRNA levels for SR Ca2+-handling proteins such as Ca2+-pump ATPase (SERCA2a), ryanodine receptor, calsequestrin and phospholamban were decreased in the ischemia-reperfused heart as compared with the non-ischemic control. Treatment with captopril improved the recovery of LVDP as well as SR Ca2+-pump ATPase and Ca2+-uptake activities in the postischemic hearts but had no effect on changes in Ca2+-release activity due to ischemic-reperfusion. Losartan neither affected the changes in contractile function nor modified alterations in SR Ca2+-handling activities. The ischemia-reperfusion induced decrease in mRNA levels for SR Ca2+-handling proteins were not affected by treatment with captopril or losartan. The results suggest that the improvement of cardiac function in the ischemic-reperfused heart by captopril is associated with the preservation of SR Ca2+-pump activities; however, it is unlikely that this action of captopril is mediated through the modification of cardiac RAS. Furthermore, cardiac RAS does not appear to contribute towards the ischemia-reperfusion induced changes in gene expression for SR Ca2+-handling proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007174803993
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  • 18
    Electronic Resource
    Electronic Resource
    Mechanisms of transcriptional activation of cAMP-responsive element-binding protein CREB (2000)
    Springer
    Molecular and cellular biochemistry 212 (2000), S. 5-9 
    Details
    ISSN: 1573-4919
    Keywords: transcriptional regulation ; gene expression ; coactivator ; repressor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The CREB-CREM transcription factors are the main gene regulatory effectors of the cAMP signaling pathway. The investigations of this family of transcription factors had a profound impact on the understanding of signaling-induced gene transcription. Here we discuss some key aspects of the underlying biology, review transcriptional activation by CREB proteins through transcription cofactors and present novel insights into the context- and position-specific function of CREB on complex genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007111818628
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  • 19
    Electronic Resource
    Electronic Resource
    Attenuation of changes in sarcoplasmic reticular gene expression in cardiac hypertrophy by propranolol and verapamil (2000)
    Springer
    Molecular and cellular biochemistry 213 (2000), S. 111-118 
    Details
    ISSN: 1573-4919
    Keywords: pressure overload ; gene expression ; subcellular remodeling ; sarcoplasmic reticulum Ca2+-handling ; anti-hypertensive therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effects of propranolol and verapamil on contractile dysfunction, subcellular remodeling and changes in gene expression in cardiac hypertrophy due to pressure overload were examined. Rats were subjected to banding of the abdominal aorta and then treated with either propranolol (10 mg/kg daily), verapamil (5 mg/kg daily) or vehicle for 8 weeks after the surgery. Depression of the left ventricular function in the hypertrophied heart was associated with decreases in myofibrillar and myosin CA2+ ATPase activities as well as Ca2+-pump and Ca2+-release activities of the sarcoplasmic reticulum (SR). The level of a-myosin heavy chain (α-MHC) mRNA was decreased while that of β-MHC mRNA was increased in the pressure-overloaded heart. The level of SR Ca2+-pump ATPase (SERCA2) mRNA and protein content for SERCA2 were decreased in the pressure overloaded heart. Treatment of the hypertrophied animals with propranolol or verapamil resulted in preservation of the left ventricular function and prevention of the subcellular alterations. Shift in the α- and β-MHC mRNA levels and changes in the expression in SERCA2 mRNA level and protein content were also attenuated by these treatments. The results suggest that blockade of β-adrenoceptors or voltage-dependent calcium channels normalizes the cardiac gene expression, prevents subcellular remodeling and thus attenuates heart dysfunction in rats with cardiac hypertrophy. Furthermore, both cardiac β-adrenoceptors and L-type Ca2+-channels may be involved in the genesis of cardiac hypertrophy due to pressure overload.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007120332587
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  • 20
    Electronic Resource
    Electronic Resource
    Cloning and characterization of the rat TIS11 gene (2000)
    Springer
    Molecular and cellular biochemistry 213 (2000), S. 119-126 
    Details
    ISSN: 1573-4919
    Keywords: TIS11 ; an immediate early gene ; gene cloning ; gene expression ; gene organization ; promoter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The TIS11 gene is an immediate early gene that is induced rapidly and transiently by phorbol 12-myristate 13-acetate and various growth factors. To study transcriptional regulation of the gene, a genomic clone of rat TIS11 was isolated, and the organization of exon-intron structure and transcriptional initiation site were determined. The rat TIS11 gene consisted of 2 exons spanning approximately 2.5 kb. Several canonical sequences for binding of transcriptional factors were found in the 5′-flanking region. The 5.3 kb of the 5′-flanking region fused to a luciferase reporter gene showed promoter activity when introduced into rat pheochromocytoma PC12 cells. Analyses with serial 5′-deletion mutants suggested that the major positive regulatory region is located at the region of -241 to -76, and that the minimum promoter region is within the 76-bp upstream of the transcriptional initiation site. Gel mobility shift assays revealed that PC12 cell nuclear proteins specifically bind to the major positive regulatory region of the TIS11 gene. The identified nuclear protein components may act as the positive trans-acting factors in the basal expression of the TIS11 gene in PC12 cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007172316657
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  • 21
    Electronic Resource
    Electronic Resource
    Cyclic Core Dendrimer as a New Kind of Vector for Gene Transfer into Mammalian Cells (2000)
    Springer
    Genetica 108 (2000), S. 53-56 
    Details
    ISSN: 1573-6857
    Keywords: dendritic polymer ; reporter gene ; gene expression ; transfection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cyclic core dendritic polymer is a new type of synthetic polymers. The ability of generation 4 of the dendrimer with a core of 1,4,7,10-tetraazacyclododecane to function as an effective gene delivery vector was investigated. Results from fluorescence in situhybridization (FISH) show that the pCH 110 plasmid DNA was transferred into human small intestine cancer metastatic ascites (HICMA) cells induced by this kind of dendrimer as a vector. The transferred LacZ, GFP and luciferase genes were highly expressed in the transfected HICMA, COS-7 and 293 cells. These studies demonstrate that the dendrimer can transfect mammalian cells in vitrowhich offers an alternatively efficient method for mammalian gene transfer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004047902652
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  • 22
    Electronic Resource
    Electronic Resource
    Proliferation of Mitochondria in Chronically Stimulated Rabbit Skeletal Muscle—Transcription of Mitochondrial Genes and Copy Number of Mitochondrial DNA (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 627-634 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondrial biogenesis ; copy number ; gene expression ; mitochondrial transcription factor ; nuclear—mitochondrial communication ; stimulation ; endurance training
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Mitochondrial proliferation was studied in chronically stimulated rabbit skeletal muscle over a period of 50 days. After this time, subunits of COX had increased about fourfold. Corresponding mRNAs, encoded on mitochondrial DNA as well as on nuclear genes, were unchanged when related to total tissue RNA, however, they were elevated two- to fivefold when the massive increase of ribosomes per unit mass of muscle was taken into account. The same was true for the mRNA encoding mitochondrial transcription factor A. Surprisingly, tissue levels of mtTFA protein were reduced about twofold, together with mitochondrial DNA. In conclusion, mito chondria are able to maintain high rates of mitochondrial transcription even in the presence of reduced mtTFA protein and mtDNA levels. Therefore, stimulated mtTFA gene expression accompanies stimulated mitochondrial transcription, as in other models, but it is not sufficient for an increase of mtDNA copy number and other, yet unknown, factors have to be postulated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005630813227
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  • 23
    Electronic Resource
    Electronic Resource
    Effects of increased and deregulated expression of cell division genes on the morphology and on antibiotic production of streptomycetes (2000)
    Springer
    Antonie van Leeuwenhoek 78 (2000), S. 269-276 
    Details
    ISSN: 1572-9699
    Keywords: differentiation ; FtsZ ; gene expression ; septum ; SsgA ; transmission electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper describes the effects of increased expression of the cell division genes ftsZ, ftsQ, and ssgA on the development of both solid- and liquid-grown mycelium of Streptomyces coelicolor and Streptomyces lividans. Over-expression of ftsZ in S. coelicolor M145 inhibited aerial mycelium formation and blocked sporulation. Such deficient sporulation was also observed for the ftsZ mutant. Over-expression of ftsZ also inhibited morphological differentiation in S. lividans 1326, although aerial mycelium formation was less reduced. Furthermore, antibiotic production was increased in both strains, and in particular the otherwise dormant actinorhodin biosynthesis cluster of S. lividans was activated in liquid- and solid-grown cultures. No significant alterations were observed when the gene dosage of ftsQ was increased. Analysis by transmission electron microscopy of an S. coelicolor strain over-expressing ssgA showed that septum formation had strongly increased in comparison to wild-type S. coelicolor, showing that SsgA clearly influences Streptomyces cell division. The morphology of the hyphae was affected such that irregular septa were produced with a significantly wider diameter, thereby forming spore-like compartments. This suggests that ssgA can induce a process similar to submerged sporulation in Streptomyces strains that otherwise fail to do so. A working model is proposed for the regulation of septum formation and of submerged sporulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010267708249
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  • 24
    Electronic Resource
    Electronic Resource
    Ethylene regulation of fruit ripening: Molecular aspects (2000)
    Springer
    Plant growth regulation 30 (2000), S. 193-200 
    Details
    ISSN: 1573-5087
    Keywords: ACC synthase ; ACC oxidase ; ethylene ; fruit ; gene expression ; regulation ; ripening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Progress in ethylene regulating fruit ripening concerning itsperception and signal transduction and expression of ACC synthaseand ACC oxidase genes is reviewed. ACC synthase and ACC oxidasehave been characterized and their genes cloned from various fruittissues. Both ACC synthase and ACC oxidase are encoded bymultigene families, and their activities are associated withfruit ripening. In climacteric fruit, the transition toautocatalytic ethylene production appears to be due to a seriesof events in which ACC sythase and ACC oxidase genes have beenexpressed developmentally. Differential expression of ACCsynthase and ACC oxidase gene family members is probably involvedin such a transition that ultimately controls the onset of fruitripening.In comparison to ACC synthase and ACC oxidase, less is knownabout ethylene perception and signal transduction because of thedifficulties in isolating and purifying ethylene receptors orethylene-binding proteins using biochemical methods. However, theidentification of the Nr tomato ripening mutant as anethylene receptor, the applications of new potent anti-ethylenecompounds and the generation of transgenic fruits with reducedethylene production have provided evidence that ethylenereceptors regulate a defined set of genes which are expressedduring fruit ripening. The properties and functions of ethylenereceptors, such as ETR1, are being elucidated.Application of molecular genetics, in combination withbiochemical approaches, will enable us to better understand theindividual steps leading from ethylene perception and signaltransduction and expression of ACC synthase and ACC oxidase genefamily member to the physiological responses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006348627110
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  • 25
    Electronic Resource
    Electronic Resource
    Biochemical and molecular aspects of fruitlet abscission (2000)
    Springer
    Plant growth regulation 31 (2000), S. 35-42 
    Details
    ISSN: 1573-5087
    Keywords: β-1,4-endoglucanase ; ethylene ; fruit ; gene expression ; polygalacturonase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Fruitlet abscission during fruit development is due to the activation ofpre-differentiated abscission zones (AZs) located between twig andpedicel, and/or pedicel and pericarp. Major advances on biochemicaland molecular aspects are related to β-1,4-endoglucanase (EG) andpolygalacturonase (PG), two cell hydrolases involved in the cell walldisassemblement responsible for fruit shedding. AZ activation isaccompanied by an increase in activity and transcript accumulation ofone or both enzymes. Expression of PG genes specifically related toabscission has been found in tomato flower AZ. In peach, an EG genehighly expressed in leaf and fruitlet AZs has been isolated. AZactivation is preceded by an induction of ethylene biosynthesis,paralleled by a stimulation of ACO activity and transcript accumulation.Ethylene, besides a dramatic stimulation of PG and EG, up or downregulates several other abscission related genes. The specificexpression of genes encoding for ethylene receptors in the AZ wouldsupport the hypothesis that fruitlet AZ specificity may depend on theability of this region to sense ethylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006338210977
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  • 26
    Electronic Resource
    Electronic Resource
    Plant responses to ultraviolet-B (UV-B: 280–320 nm) stress: What are the key regulators? (2000)
    Springer
    Plant growth regulation 32 (2000), S. 27-39 
    Details
    ISSN: 1573-5087
    Keywords: ethylene ; gene expression ; jasmonic acid ; reactive oxygen species ; salicylic acid ; ultraviolet-B radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Depletion of the stratospheric ozone layer is leadingto an increase in ultraviolet-B (UV-B: 280–320 nm)radiation reaching the earth's surface. This hasraised interest in the possible consequence ofincreased UV-B levels on plant growth and developmentand the mechanisms underlying these responses. Although the effects of UV-B are now wellcharacterised at the physiological level, little isknown about the cellular and molecular mechanismsinvolved. Recent studies have shown that UV-B affectsa number of important physiological processes, such asphotosynthesis, through effects on gene expression. In addition, induction of a number of defensemechanisms, such as production of UV-B screeningpigments, increase in antioxidant enzymes andinduction of pathogenesis-related proteins, are alsomediated at the level of gene expression. The signaltransduction pathways by which UV-B regulates geneexpression are at present poorly understood. Thestudies carried out to date have, however, indicateda pivotal role for reactive oxygen species as keysecond messengers acting up-stream of a number ofpathways involving the plant hormones salicylic acid,jasmonic acid and ethylene. The transduction pathwaysidentified to date and the role of intermediates inregulating tolerance to UV-B damage are discussed inthis review.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006314001430
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  • 27
    Electronic Resource
    Electronic Resource
    Resistance to wheat leaf rust in Aegilops tauschii Coss. and inheritance of resistance in hexaploid wheat (2000)
    Springer
    Genetic resources and crop evolution 47 (2000), S. 135-140 
    Details
    ISSN: 1573-5109
    Keywords: Aegilops tauschii ; gene expression ; genetic inheritance ; Puccinia recondita f. sp. tritici ; rust resistance ; synthetic hexaploid wheats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A collection of 164 Aegilops tauschii accessions, obtained from Gatersleben, Germany, was screened for reaction to leaf rust under controlled greenhouse conditions. We have also evaluated a selection of synthetic hexaploid wheats, produced by hybridizing Ae. tauschii with tetraploid durum wheats, as well as the first and second generation of hybrids between some of these resistant synthetic hexaploid wheats and susceptible Triticum aestivum cultivars. Eighteen (11%) accessions of Ae. tauschii were resistant to leaf rust among which 1 was immune, 13 were highly resistant and 4 were moderately resistant. Six of the synthetic hexaploid wheats expressed a high level of leaf rust resistance while four exhibited either a reduced or complete susceptibility compared to their corresponding diploid parent. This suppression of resistance at the hexaploid level suggests the presence of suppressor genes in the A and/or B genomes of the T. turgidum parent. Inheritance of leaf rust resistance from the intercrosses with susceptible bread wheats revealed that resistance was dominant over susceptibility. Leaf rust resistance from the three synthetics (syn 101, syn 701 and syn 901) was effectively transmitted as a single dominant gene and one synthetic (syn 301) possessed two different dominant genes for resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008770226330
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  • 28
    Electronic Resource
    Electronic Resource
    Mechanisms regulating differential freezing tolerance of suspension cell cultures derived from contrasting alfalfa genotypes (2000)
    Springer
    Plant cell, tissue and organ culture 61 (2000), S. 143-151 
    Details
    ISSN: 1573-5044
    Keywords: fall dormancy ; gene expression ; Medicago sativa L. ; protein ; starch ; sugar ; winter hardiness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A major factor limiting persistence of alfalfa (Medicago sativa L.) in the northern US is poor winter hardiness. Our hypothesis is that suspension cell cultures derived from dormant, winter-hardy alfalfa cultivars would cold acclimate and survive sub-zero temperatures better than cell cultures derived from non-dormant, non-hardy cultivars. Our objectives were (1) to determine if genetic differences in winter hardiness between dormant and non-dormant alfalfa were retained by suspension cells derived from these contrasting cultivars; and (2) to determine the physiological and biochemical bases for differences in freezing tolerance of suspension cells. Cell suspensions derived from `5262' (fall dormant) and `5929' (fall non-dormant) were cold hardened at 2 °C for 14 days. Cells were frozen in a cooling bath and cell survival determined by measuring 2, 3, 5-triphenyltetrazolium chloride (TTC) reduction. Cold acclimation improved cell survival of both cultivars to −5 °C when compared to unacclimated cells. Only acclimated cells of 5262 survived temperatures of −10 °C to −25 °C. The freezing tolerance of cold-acclimated 5262 cells was associated with high sugar and starch concentrations, lower α-amylase activities and slightly lower cell protein levels when compared to 5929. No differences in polypeptide composition were evident when comparing acclimated and unacclimated cells of 5929, but polypeptide composition did change with acclimation of 5262 cells. As expected, expression of RootCAR1 in 5262 cells increased with cold acclimation, but high levels of RootCAR1 transcript were unexpectantly found in both cold acclimated and unacclimated 5929 cells. With the exception of the RootCAR1 expression, many of the physiological responses of these alfalfa cell lines to cold acclimation were similar to those that have been reported for field-grown plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006408829105
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  • 29
    Electronic Resource
    Electronic Resource
    Regulation of NADPH-cytochrome P450 reductase expressed during Douglas-fir germination and seedling development (2000)
    Springer
    Plant molecular biology 44 (2000), S. 141-153 
    Details
    ISSN: 1573-5028
    Keywords: gene expression ; germination ; NADPH-cytochrome P450 reductase ; Pseudotsuga menziesii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract NADH-cytochrome P450 is a key enzyme that transfers electrons from NADPH to the cytochrome P450 family of enzymes. To begin to determine the regulation of CPR gene expression and enzyme activity in Douglas-fir a full-length cDNA was isolated from a seedling λZAP cDNA library and the ORF was used to develop a synthetic CPR-peptide-based antiserum. Northern blot analysis indicated CPR expression was regulated both developmentally prior to seed maturation and during germination, and differentially in the cotyledons, radicle and megagametophyte of seed and seedling tissues. The CPR-peptide antiserum detected a single CPR in seed and seedling microsomes analyzed by western blot of two-dimensional SDS-polyacrylamide gels. In microsomal extracts from whole seeds and seedlings, the amount of CPR protein remained constant while NADPH:cytochrome c reductase activity increased during stratification, germination and early seedling development. In contrast to cotyledons and megagametophyte, the level of CPR protein detected in radicles was higher than expected when compared to the amount of CPR transcript.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006425025702
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  • 30
    Electronic Resource
    Electronic Resource
    Molecular characterization of quinolinate phosphoribosyltransferase (QPRTase) in Nicotiana (2000)
    Springer
    Plant molecular biology 44 (2000), S. 603-617 
    Details
    ISSN: 1573-5028
    Keywords: gene expression ; nicotinic acid ; pyridine alkaloids ; secondary metabolism ; polyploidy ; wound-induced
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Quinolate acid phosphoribosyltransferase (QPRTase), a key enzyme in nicotinamide adenine dinucleotide (NAD) biosynthesis, also plays an important role in ensuring nicotinic acid is available for the synthesis of defensive pyridine alkaloids in Nicotiana species. In this study, cDNAs for QPRTase were characterized from N. rustica and N. tabacum. Deduced proteins from both cDNAs are almost identical and contain a 24 amino acid N-terminal extension, not reported in other QPRTases, that has characteristics of a mitochondrial targeting sequence. In N. tabacum and N. sylvestris, both of which contain nicotine as the major pyridine alkaloid, QPRTase transcript was detected in roots, the site of nicotine synthesis, but not in leaves. QPRTase transcript levels increased markedly in roots of both species 12–24 h after damage to aerial tissues, with a concomitant rise in transcript levels of putrescine N-methyltransferase (PMT), another key enzyme in nicotine biosynthesis. In N. glauca, however, in which anabasine represents the major pyridine alkaloid, QPRTase transcript was detected in both leaf and root tissues. Moreover, wound induction of QPRTase but not PMT was observed in leaf tissues, and not in roots, 12–24 h after wounding. Southern analysis of genomic DNA from the Nicotiana species noted above, and also several others from within the genus, suggested that QPRTase is encoded by a small gene family in all the species investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026590521318
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  • 31
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    Electronic Resource
    The nitrate reductase promoter of birch directs differential reporter gene expression in tissues of transgenic tobacco (2000)
    Springer
    Plant and soil 221 (2000), S. 33-38 
    Details
    ISSN: 1573-5036
    Keywords: ammonium ; birch ; gene expression ; nia promoter ; nitrate ; nitrate reductase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A 1535 bp promoter of the nitrate reductase gene (nia) from birch (Betula pendula) and a series of 5′ deletions were fused to the β-glucuronidase (GUS) gene and introduced into Nicotiana plumbaginifolia. In transgenic plants the NR promoter sequences directed strong GUS expression in the root epidermal hair cells, and in phloem cells of leaf and stem vascular tissue. The NR promoter confers also a significant stimulation of the GUS gene expression by nitrate. These findings might indicate that nitrate flow is one of the signals involved into tissue and cell specific expression of the NR promoter GUS fusions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004739621352
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  • 32
    Electronic Resource
    Electronic Resource
    Binding of cell type-specific nuclear proteins to the 5′-flanking region of maize C4 phosphoenolpyruvate carboxylase gene confers its differential transcription in mesophyll cells (2000)
    Springer
    Plant molecular biology 44 (2000), S. 543-557 
    Details
    ISSN: 1573-5028
    Keywords: C4 photosynthesis ; maize ; phosphoenolpyruvate carboxylase ; transgenic plant ; transcription ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract C4-type phosphenolpyruvate carboxylase (C4PEPC) acts as a primary carbon assimilatory enzyme in the C4 photosynthetic pathway. The maize C4PEPC gene (C4Ppc1) is specifically expressed in mesophyll cells (MC) of light-grown leaves, but the molecular mechanism responsible for its cell type-specific expression has not been characterized. In this study, we introduced a chimeric maize C4Ppc1 5′-flanking region/β-glucuronidase (GUS) gene into maize plants by Agrobacterium-mediated transformation. Activity assay and histochemical staining showed that GUS is almost exclusively localized in leaf MC of transgenic maize plants. This observation suggests that the introduced 5′ region of maize C4Ppc1 contains the necessary cis element(s) for its specific expression in MC. Next, we investigated whether the 5′ region of the maize gene interacts with nuclear proteins in a cell type-specific manner. By gel shift assays with nuclear extracts prepared from MC or bundle sheath cells (BSC), cell type-specific DNA-protein interactions were detected: nuclear factors PEPIb and PEPIc are specific to MC whereas PEPIa and PEPIIa are specific to BSC. Light alters the binding activity of these factors. These interactions were not detected in the assay with nuclear extract prepared from root, or competed out by oligonucleotides corresponding to the binding sites for the maize nuclear protein, PEP-I, which is known to bind specifically to the promoter region of C4Ppc1. The results suggest that novel cell type-specific positive and negative nuclear factors bind to the maize C4Ppc1 5′-flanking region and regulate its differential transcription in MC in a light-dependent manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026565027772
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  • 33
    Electronic Resource
    Electronic Resource
    Molecular approaches to study plasma membrane H+-ATPases in arbuscular mycorrhizas (2000)
    Springer
    Plant and soil 226 (2000), S. 219-225 
    Details
    ISSN: 1573-5036
    Keywords: arbuscular mycorrhizas ; gene expression ; Glomus mosseae ; nutrient transport processes ; plasma membrane H+-ATPases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The activity of H+-ATPases of plant and fungi generates an electrochemical gradient of H+ across the cell plasma membrane that drives a number of secondary transport systems, including those responsible for the translocation of cations, anions, amino acids and sugars. During the last years, several studies have been aimed at elucidating the role of plasma membrane H+-ATPases in the nutrient exchange processes taking place between the plant and the fungus in arbuscular mycorrhizal (AM) symbiosis. This paper reviews present knowledge about plasma membrane H+-ATPases and experimental evidence supporting the involvement of H+-ATPases of both organisms in the bidirectional transport of nutrients between partners. Molecular strategies that will provide further information on the function and regulation of plasma membrane H+-ATPases in AM symbiosis are presented and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026469109773
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  • 34
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    Electronic Resource
    Kidney ischemia-reperfusion: Modulation of antioxidant defenses (2000)
    Springer
    Molecular and cellular biochemistry 205 (2000), S. 1-11 
    Details
    ISSN: 1573-4919
    Keywords: kidney ; ischemia-reperfusion injury ; free radicals ; reactive oxygen species ; gene expression ; antioxidant enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Reactive oxygen species (ROS; O2-, H2O2, and OH·), normal by-products of cellular metabolic processes, are kept in control by antioxidant enzymes, such as catalase, glutathione peroxidase (GPX) and superoxide dismutases (SODs). To understand the role of antioxidant enzymatic defenses against ROS injury following ischemia-reperfusion, we examined the effect on kidney exposed to varying periods (30, 60 or 90 min) of ischemia followed by different periods of reperfusion. The enzymatic activities and protein levels of catalase, GPX, CuZnSOD and MnSOD were relatively unaffected at 30 min of ischemia followed by 0, 2 or 24 h reperfusion. However, 60 or 90 min of ischemia followed by 0, 2 or 24 h of reperfusion resulted in a decrease in activities and protein levels which paralleled the duration of ischemic injury. MnSOD activity tended to recover towards normal during reperfusion. Examination of the mRNA levels of these antioxidant enzymes demonstrated a severe decrease in mRNA levels of catalase and GPX at a time point of minimal ischemic injury (30 min of ischemia followed by reperfusion) suggesting that loss of mRNA of catalase and GPX may be the first markers of alterations in cellular redox in ischemia-reperfusion injury. Greater loss of mRNA for catalase, GPX and CuZnSOD were observed following longer periods (60 or 90 min) of ischemia. The mRNA for MnSOD was upregulated at all time points of ischemia-reperfusion injury. Actually, the greater decrease in mRNAs for catalase, GPX and CuZnSOD in the acute phase (within 24 h) subsequently showed a further decrease in these enzyme activities in the subacute phase (72 or 120 h after ischemia). These enzyme activities in the 30 min ischemia group, but not in the 90 min group, already showed tendencies for normalization at 120 h after ischemia. To understand the molecular basis of the loss of mRNA of these antioxidant enzymes during ischemia-reperfusion injury, we examined the rate of transcription by nuclear run-on assays. The similar rates of transcription in control and kidney exposed to ischemia-reperfusion indicates that the loss of mRNA for catalase, GPX and CuZnSOD are possibly due to the increased rate of turnover of their mRNAs. These studies suggest that expression of antioxidant genes during ischemia-reperfusion are not coordinately expressed and the differential loss of antioxidant enzymes may be the contributing factor(s) towards the heterogeneous renal tissue damage as a result of ischemia-reperfusion induced oxidative stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007047505107
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    Electronic Resource
    Apolipoprotein E gene expression is reduced in apolipoprotein A-I transgenic mice (2000)
    Springer
    Molecular and cellular biochemistry 209 (2000), S. 125-129 
    Details
    ISSN: 1573-4919
    Keywords: apolipoprotein E ; apolipoprotein A-I ; gene expression ; transgenic mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The levels of plasma apolipoprotein (apo) E, an anti-atherogenic protein involved in mammalian cholesterol transport, were found to be 2-3 fold lower in mice over-expressing human apoA-I gene. ApoE is mainly associated with VLDL and HDL-size particles, but in mice the majority of the apoE is associated with the HDL particles. Over-expression of the human apoA-I in mice increases the levels of human apoA-I-rich HDL particles by displacing mouse apoA-I from HDL. This results in lowering of plasma levels of mouse apoA-I. Since plasma levels of apoE also decreased in the apoA-I transgenic mice, the mechanism of apoE lowering was investigated. Although plasma levels of apoE decreased by 2-3 fold, apoB levels remained unchanged. As expected, the plasma levels of human apoA-I were almost 5-fold higher in the apoAI-Tg mice compared to mouse apoA-I in WT mice. If the over-expression of human apoA-I caused displacement of apoE from the HDL, the levels of hepatic apoE mRNA should remain the same in WT and the apoAI-Tg mice. However, the measurements of apoE mRNA in the liver showed 3-fold decreases of apoE mRNA in apoAI-Tg mice as compared to WT mice, suggesting that the decreased apoE mRNA expression, but not the displacement of the apoE from HDL, resulted in the lowering of plasma apoE in apoAI-Tg mice. As expected, the levels of hepatic apoA-I mRNA (transgene) were 5-fold higher in the apoAI-Tg mice. ApoE synthesis measured in hepatocytes also showed lower synthesis of apoE in the apoAI-Tg mice. These studies suggest that the integration of human apoA-I transgene in mouse genome occurred at a site that affected apoE gene expression. Identification of this locus may provide further understanding of the apoE gene expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007107712725
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    Regulation of Keratinocyte Growth Factor (KGF) and KGF Receptor mRNAs by Nutrient Intake and KGF Administration in Rat Intestine (2000)
    Springer
    Digestive diseases and sciences 45 (2000), S. 736-743 
    Details
    ISSN: 1573-2568
    Keywords: keratinocyte growth factor ; KGF receptor ; gene expression ; intestine ; nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this study was to investigate the regulation of keratinocyte growth factor (KGF) and KGF receptor mRNAs by diet and KGF treatment in rat intestine. Fasting for three days up-regulated KGF and KGF receptor mRNA levels in ileum and increased KGF receptor mRNA expression in colon. KGF and KGF receptor mRNA levels returned toward control values with ad libitum refeeding but remained elevated when refeeding was limited to 25% of ad libitum intake. KGF treatment during nutrient repletion did not alter intestinal KGF mRNA levels but increased KGF receptor mRNA abundance in ileum and colon. We conclude that the increase in KGF and KGF receptor mRNAs induced by malnutrition may be an adaptive response to attenuate gut mucosal atrophy in this setting. The gut-trophic effects of KGF treatment may be mediated, in part, by up-regulation of the KGF receptor mRNA in small bowel and colon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005447827579
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    Electronic Resource
    Gene expression in allergenic pollen (2000)
    Springer
    Aerobiologia 16 (2000), S. 331-334 
    Details
    ISSN: 1573-3025
    Keywords: allergenic pollen ; gene expression ; molecular biology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The molecular mechanism of gene expression for pollen specificity is not yet fully known. However, it is an exciting area with great potential and has a wide scope of application in the field of molecular biology, breeding systems, biotechnology etc. The main aim of this write-up is to review some of the interesting achievements made through studies like gene expression in allergic pollen and the research which will make a way towards practical application of pollen molecular biology in identifying and isolating the genes responsible for all allergic disorders reported among various individuals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026515820294
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  • 38
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    Electronic Resource
    Expression and activity of antioxidant enzymes during potato tuber dormancy (2000)
    Springer
    Potato research 43 (2000), S. 383-393 
    Details
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; plant development ; antioxidant genes ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The expression of antioxidant genes has been analyzed in a potato plant and during tuber dormancy. Manganese superoxide dismutase (MnSOD), cytosolic copper and zinc superoide dismutase (Cu/ZnSOD), catalase class II, cytosolic ascorbate peroxidase (APX) and glutathione peroxidase (GPX) are expressed at the RNA level in all the contexts analyzed. By contrast, the expression of the iron superoxide dismutase (FeSOD) and plastidic Cu/ZnSOD seems to be limited to green tissues, as shown by northern blots and native gels. A complex DAB-peroxidase isozyme pattern (using diaminobenzidine as substrate) has been observed in different developmental contexts analyzed, but hardly observed in tubers. During tuber dormancy, MnSOD and cytosolic Cu/ZnSOD activity was relatively constant in both Désirée and Bintje varieties while catalase activity decreases. Moreover, tuber dormancy breakage did not involve significant changes in the activity of these enzymes. On the basis of these results, the possible link between active oxygen species (AOS) metabolism and dormancy is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02360542
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    Functional genomic analysis of potato tuber life-cycle (2000)
    Springer
    Potato research 43 (2000), S. 297-312 
    Details
    ISSN: 1871-4528
    Keywords: gene expression ; cDNA-AFLP ; RNA-fingerprinting ; organogenesis ; tuberisation ; dormancy ; sprouting ; cluster analysis ; metabolic pathways
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Potato tuber life-cycle is composed of many individual developmental stages including tuber formation, tuber development, dormancy and sprouting. We have used cDNA-AFLP fingerprinting to analyse gene expression in 24 individual stages of development, over the period from stolon formation through sprouting. In addition to these developmental stages, different tissues were analysed to assess tissue specificity and various controls were incorporated to determine process specificity. In total around 18000 transcript derived cDNA fragments (TDFs) were visualised from which circa 2600 were included in a statistical analysis allowing general conclusions about gene expression during development. More than 200 process specific TDFs were isolated and sequenced throughout the potato tuber life-cycle. The sequence similarities of these TDFs to known genes give an insight into the kinds of processes occurring during tuberisation, dormancy and sprouting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02360536
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  • 40
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    Triphenylpyrylium Tetrafluoroborate-Sensitized Photochemistry of the Terpenes Sabinene, α-Phellandrene, and α- and γ-Terpinene (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1563-1567 
    Details
    ISSN: 1434-193X
    Keywords: Triplet recombination ; Electron transfer ; Radical ions ; Photochemistry ; Terpenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The triphenypyrylium tetrafluoroborate (TPT)-sensitized reactions of several terpene donor molecules, including sabinene (1), α-phellandrene (4), α-terpinene (5) and γ-terpinene (6) give rise to significantly different products than reactions induced by other electron-transfer sensitizers, such as 1,4-dicyanobenzene (DCB). The divergent reactions require decidedly different key intermediates; the products obtained with TPT can be explained by dissociative recombination of the intermediate radical-radical cation pair in the triplet state, generating donor-derived biradicals.
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  • 41
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    Electronic Resource
    Ring Expansion of 2-Alkylidenedihydroquinazolines to Iminodihydro-1,4-benzodiazepines by Methanesulfonyl and Trifluoromethanesulfonyl Azide (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1577-1587 
    Details
    ISSN: 1434-193X
    Keywords: Azides ; Cleavage reactions ; Cycloadditions ; Nitrogen heterocycles ; Polycycles ; Ring expansion ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---2-Alkyl-1-methylquinazolinium hexafluorophosphates 9 are deprotonated by sodium or potassium hydride to afford solutions of 2-alkylidenedihydroquinazolines 10, which were investigated by NMR spectroscopy. Trapping with methanesulfonyl azide (5a) of 10 in situ or subsequent treatment with trifluoromethanesulfonyl azide (5b) gives mixtures of colourless (15) and intensely yellow N-sulfonylimino-1,4-benzodiazepines 16 along with products due to cleavage of the exocyclic double bond of 10, viz. 11 and 13. The ethylidene compound 10b yields the bicyclic products 18 and 19, apparently by complex sequences of reactions that are triggered by removal of the acidic proton at C-2 of 16b and 16f. The structures of the products are based on spectroscopic evidence and X-ray diffraction analyses performed on 15b, 16d, 16e, and 19.
    Additional Material: 6 Ill.
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  • 42
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    Electronic Resource
    Electrophilic Reactivity of a 2-Azaallenium and of a 2-Azaallylium Ion (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1589-1593 
    Details
    ISSN: 1434-193X
    Keywords: Azaallenium ions ; Azaallylium ions ; Iminium ion ; Kinetics ; Linear Free Energy Relationships ; Ab initio calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The rate constants for the reactions of the 2-azaallenium ion 1b+, the 2-azaallylium ion 2a+ and the iminium ion 3+ with different nucleophiles were determined by 1H NMR spectroscopy. By correlation with the Linear Free Enthalpy Relationship (LFER) lg k20°C = s (E + N), developed by Mayr and Patz, the electrophilicity parameters E(1b+) = -3.7, E(2a+) ≍ -16 and E(3+) = -10.43 were obtained. They show that the relative reactivities of these ions are approximately 1012:1:106. Quantum chemical calculations (ab initio, DFT) of the methyl anion affinities for the ions 1b+,2a+ and3+ are in agreement with the experimental E values. The X-ray structure of 3+·CF3SO3- is reported for the first time; it shows no strong interaction between the cation and the anion.
    Additional Material: 2 Ill.
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  • 43
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    Oxazoline N-Oxide Mediated [3+2] Cycloadditions: Application to a Formal Synthesis of a (+)-β-Methylcarbapenem (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1595-1601 
    Details
    ISSN: 1434-193X
    Keywords: Oxazoline N-oxide ; Cycloadditions ; Cycloadditions ; Lactams ; Thienamycin ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---[3+2] Cycloaddition between a camphor-derived oxazoline N-oxide 9 and the γ,δ-unsaturated enamino ester 11 afforded the single adduct 6. A stereoselective reduction of the enamino ester side chain allowed the control of the absolute configuration of the two additional asymmetric centres. Nitrogen protection and oxidative hydrolysis of the resulting product 13, followed by further functional group manipulations, led to the β-lactam derivative 1, a known precursor of the β-methylthienamycin derivative2a.
    Additional Material: 1 Ill.
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  • 44
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    A New Substitution Pattern in Subphthalocyanines: Regioselective Synthesis and Separation of “ortho” Derivatives (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1603-1607 
    Details
    ISSN: 1434-193X
    Keywords: Boron ; Cyclotrimerizations ; Nitrogen heterocycles ; Macrocycles ; Subphthalocyanines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The regioselective preparation of ortho-substituted subphthalocyanides was achieved employing 3-substituted phthalonitrile derivatives as starting materials. A mechanistic proposal has been outlined.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/99525_s.pdf or from the author.
    Additional Material: 2 Ill.
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  • 45
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    A New Route to 2,7- and 7-Functionalized Labdanes (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1609-1615 
    Details
    ISSN: 1434-193X
    Keywords: Terpenoids ; Natural products ; Total synthesis ; Cyclizations ; Rearrangements ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A new route for the synthesis of 2,7- and 7-functionalized labdanes starts from (R)-carvone (1). 11-Nordrim-7-en-9-one (15) is an appropriate starting material for the total synthesis of hispanone (21), a biologically active furolabdane isolated from the Mediterranean medicinal plant Ballota saxatilis.
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    Preparation of Kingiside from Aucubin (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1623-1626 
    Details
    ISSN: 1434-193X
    Keywords: Iridoid glucoside ; (8S)-Kingiside ; (8S)-Loganin ; (8S)-7-Ketologanin ; Asymmetric synthesis ; Natural products ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The tetraacetyl derivative 8 of the naturally occurring kingiside (8a) was prepared from aucubin (1). Intermediates in the synthesis were (8S)-tetraacetyl loganin (6) and (8S)-tetraacetyl-7-ketologanin (7), whose free (8R)-epimers occur in many different plants (Caprifoliaceae, Loganiaceae). The 13C NMR spectrum allows the structure to be unequivocally identified.
    Additional Material: 1 Tab.
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  • 47
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    Ring Closure Reactions of Disubstituted 4-Penten-1-oxyl Radicals - Towards a Stereoselective Synthesis of allo-Muscarine (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1677-1683 
    Details
    ISSN: 1434-193X
    Keywords: Radicals ; Cyclizations ; Pyridinethione ; Tetrahydrofurans ; Asymmetric synthesis ; Thiazolethione ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The trisubstituted functionalized tetrahydrofurans 10, 11, 16, 18, and 19 were photochemically prepared from 2,3-syn- and 2,3-anti-configuredN-(3-benzoyloxy-5-hexen-2-oxy)thiazole-2(3H)-thione anti-6, pyridinethiones 7, anti-8, and BrCCl3. The formation of tetrahydrofurans was achieved by an efficient and highly regioselective alkoxyl radical cyclization (5-exo-trig). The 2,3-anti substituted intermediates 9 and 12 cyclize stereoselectively whereas a 2,3-syn-configured O-radical affords both possible diastereomeric addition products in equal amounts. The cyclized tetrahydrofuryl methyl radicals were trapped with the bromine atom donor BrCCl3 to afford the bromomethyl-substituted cyclic ethers 10, 11, 18, and 19 in excellent yields. The utility of this reaction was stressed by conversion of one of the newly prepared tetrahydrofurans in a two-step synthesis into (+)-allo-muscarine (+)-20.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/99590_s.pdf or from the author.
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  • 48
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    The Formation of 1,3-Dithiolanes from Aromatic Thioketones and Diazomethane - The Mechanism of the Schönberg Reaction (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1685-1694 
    Details
    ISSN: 1434-193X
    Keywords: Thioketones ; Thiocarbonyl ylides ; Cycloadditions ; Cycloreversions ; Sulfur heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Reactions of diaryl thioketones with diazomethane at room temperature afford 4,4,5,5-tetraaryl-1,3-dithiolanes; the scope of this surprising 2:1 interaction has been studied for decades (Schönberg Reaction). The clue to the mechanism was our observation that the stoichiometry is 1:1 at -78 °C, and 2,5-dihydro-2,2-diaryl-1,3,4-thiadiazoles are formed as primary [2+3] cycloadducts. They lose N2 at -45 °C in first-order reactions generating diaryl thioketone S-methylides which can be intercepted by thioketones (→1,3-dithiolanes), multiple CC bonds, or acids HX. In the absence of trapping reagents, the elusive intermediates either dimerize furnishing 2,2,3,3-tetraaryl-1,4-dithianes or give rise to 2,2-diarylthiiranes by electrocyclization. Beyond thiobenzophenone and diazomethane, our main model reaction, the studies involve fluorene-9-thione, 4,4-dimethoxy- and 4,4-dichlorothiobenzophenone. The ring of 2,5-dihydro-2,2-diphenyl-1,3,4-thiadiazole (8) is opened by LDA at -78 °C and derivatives of anion 12 are obtained. - In summa: The Schönberg reaction consists of two 1,3-dipolar cycloadditions, linked by a 1,3-dipolar cycloreversion.
    Additional Material: 1 Ill.
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  • 49
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    Reactions of Thiobenzophenone S-Methylide with Thiocarbonyl Compounds (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1695-1702 
    Details
    ISSN: 1434-193X
    Keywords: Thiocarbonyl ylides ; Cycloadditions ; Dithiolanes ; Sulfur heterocycles ; Thioketones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---2,5-Dihydro-2,2-diphenyl-1,3,4-thiadiazole (4) eliminates N2 at -45 °C and generates thiobenzophenone S-methylide (5), which is intercepted by dipolarophiles. The 1,3-cycloadditions of 5 with thiones (aromatic and aliphatic thioketones, dithioesters, trithiocarbonate) furnish 1,3-dithiolanes 7, in which the substituents, even voluminous ones, appear in the proximal 4- and 5-positions. The reaction of 5 with adamantanethione furnishes 7h and 4,4,5,5-tetraphenyl-1,3-dithiolane (7a) in a ratio of 4:1; a methylene transfer is involved, and the mechanistic pathways are discussed. The cycloadduct 7f originating from 5 and diphenyl trithiocarbonate undergoes an isomerization which consists of ionization and ring-opening leading to a ketene dithioacetal structure.
    Additional Material: 2 Ill.
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    Synthesis and α-Mannosidase Inhibitory Activity of Three Deoxy Derivatives of Mannostatin A (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1759-1765 
    Details
    ISSN: 1434-193X
    Keywords: Cyclitols ; Aminocyclitols ; Glycosidase inhibitors ; α-Mannosidase inhibitors ; Deoxygenation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Three deoxy derivatives 2-4 of the α-mannosidase inhibitor mannostatin A (1) were synthesized, and their inhibition of Jack bean α-mannosidase was evaluated in order to elucidate the roles of each of the three hydroxyl groups of the inhibitor. The 1- and 2-deoxy derivatives 2 and 3 retained some inhibitory activity, although reduced by a factor of about 100 relative to the parent, whereas it was completely lost with the 3-deoxy derivative 4. Structure and activity relationships are discussed in the light of these findings.
    Additional Material: 1 Tab.
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    A Circular Dichroism Approach to the Conformation of 1-Arylethylamino-Substituted 1,3,5-Triazine Derivatives (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1767-1772 
    Details
    ISSN: 1434-193X
    Keywords: Circular dichroism ; Conformation analysis ; s-Triazines ; Chiral auxiliaries ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---CD data of the optically pure 2-[(R)-1-(9-anthryl)ethylamino]-4-chloro-6-[(R)-1-(1-naphthyl)ethylamino]-1,3,5-triazine, 2[(R)-1-(9-anthryl)ethylamino]-4,6-bis[(R)-1-(1-naphthyl)ethylamino]-1,3,5-triazine, 2,4-bis[(R)-1-(9-anthryl)ethylamino]-6-chloro-1,3,5-triazine are presented. The analysis of the CD spectra by means of the nonempirical DeVoe approach has afforded the complete conformational characterisation of the three s-triazine derivatives, allowing us to establish how the conformation of these derivatives depends on the nature of the substituent 1-arylethylamino groups.
    Additional Material: 6 Ill.
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  • 52
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    Solid-Acid Catalysed Rearrangement of Cyclic α,β-Epoxy Ketones (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1905-1911 
    Details
    ISSN: 1434-193X
    Keywords: α,β-Epoxy ketones ; Rearrangements ; Zeolites ; Clays ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Various cyclic α,β-epoxy ketones rearranged to α-formyl ketones and/or vic-diones in the presence of catalytic amounts of zeolites and montmorillonite K10. This provides an excellent alternative to conventional homogeneous systems with respect to yields and workup. Differences in product distribution and type of products in the rearrangement of pulegone oxide could be reasonably explained by invoking different pathways for homogeneous and heterogeneous catalysts.
    Additional Material: 4 Tab.
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    Enantioselective Synthesis of Hydroxy-Substituted DBN-Type Amidines as Potential Chiral Catalysts (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 105-113 
    Details
    ISSN: 1434-193X
    Keywords: Amidines ; Chiral bases ; Enantioselective catalysis ; Enantioselective synthesis ; N-acyliminium ions ; Oxazaborolidines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The synthesis and X-ray crystal structures of three enantiopure hydroxy-substituted amidines of the DBN-type are described. The key starting material, a 5-(phenylsulfonyl)pyrrolidin-2-one, was obtained by an oxazaborolidine-catalysed reductive desymmetrization of a meso-imide and was functionalized through N-acyliminium ion chemistry. The hydroxy groups were introduced by ozonolysis or reduction. Preliminary results on the use of the hydroxyamidines as chiral, bifunctional catalysts in selected Michael reactions are described.
    Additional Material: 3 Ill.
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    A New Approach to N-Methylaspartic, N-Methylglutamic, and N-Methyl-α-aminoadipic Acid Derivatives (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 199-204 
    Details
    ISSN: 1434-193X
    Keywords: Hexafluoroacetone ; N-Methylaspartic acid ; N-Methylglutamic acid ; N-Methyl-α-aminoadipic acid ; N-Methylthiazol-4-yl-α-amino acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-Methylaspartic acid derivatives and its homologues are obtained by a stereoconservative one-pot procedure from hexafluoroacetone-protected aspartic and glutamic acid, 2a and 2b, respectively. α-Aminoadipic acid (5c) and its derivative 6c are accessible from the corresponding glutamic acid derivative 9b by a Wolff rearrangement. A variety of homochiral N-methylamino acids, 5 and 12, and their derivatives, 6 and 8-11, become readily available by the new synthetic concept.
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  • 55
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    Electronic Resource
    Substituent Effects on Redox Properties and Photoinduced Electron Transfer in Isoxazolo-Fullerenes (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 455-465 
    Details
    ISSN: 1434-193X
    Keywords: Fullerenes ; Cycloadditions ; Donor-acceptor systems ; Cyclic voltammetry ; Photoinduced electron transfer ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The new C60 and C70 adducts 1b, 1d-1k, 1m, 6d, 7d, and 8d have been synthesized by [2+3] cycloadditions of the appropriate nitrile oxides. Variations in the distance and geometry of the donor and acceptor substituents are seen to have an influence on the redox behavior of the fullerene adducts in cyclic voltammetry experiments. The isoxazolo-fullerenes 1c, 1d, and 1i show shifts of about 30 mV or 40 mV to more negative values compared with the reference compound 1a. On the other hand, strong acceptor properties are detected in the case of compound 1e, which shows a positive shift of 30 mV relative to 1a. Moreover, time-resolved fluorescence spectroscopy has shown that upon excitation of the fullerene moiety in the polar solvent benzonitrile, an electron is transferred from the donor substituent to the first excited singlet state of the fullerene, thereby reducing the excited-state lifetime. Our data demonstrate that the electron-transfer rate in donor-substituted fullerenes can be controlled by the electron-donating property of the substituent as well as the electronic structure and/or length of the spacer used. The C70 regioisomers 6d, 7d, and 8d exhibit differences in their spectroscopic characteristics.
    Additional Material: 3 Ill.
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  • 56
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    Electronic Resource
    Synthesis of Nucleoside Triphosphates that Contain an Aminooxy Function for “Post-Amplification Labelling” (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 211-217 
    Details
    ISSN: 1434-193X
    Keywords: Aminooxy group ; Phosphorylations ; Nucleotides ; Fluorescent labelling ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Preparation of the uridine and adenosine triphosphates 1 and 2 bearing a linker with a terminal aminooxy group is described. Both 1 and 2 react readily with the aldehydic fluorescein derivative 15. They could each be incorporated into a 330-mer fragment with T7 RNA polymerase.
    Additional Material: 2 Ill.
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  • 57
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    Electronic Resource
    Syntheses, Structures and Basicities of 1,2,4,5-Tetrakis(dimethylamino)benzene and 2,3,6,7-Tetrakis(dimethylamino)naphthalene (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 327-333 
    Details
    ISSN: 1434-193X
    Keywords: “Proton sponge” analogues ; Orientation dependence of hydrogen bonds ; Crystal structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---1,2,4,5-Tetrakis(dimethylamino)benzene (4) and 2,3,6,7-tetrakis(dimethylamino)naphthalene (5) were prepared and structurally determined. Electron-donor functions, protonation, and the geometry of intramolecular hydrogen bonds are discussed. By oxidation of 4 to its dication the benzenoid aromaticity is cancelled in favour of two independent cyanine-type units as determined by X-ray structure analysis.
    Additional Material: 4 Ill.
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  • 58
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    Electronic Resource
    Novel Fluorescent Dyes by the Extension of the Core of Perylenetetracarboxylic Bisimides (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 365-380 
    Details
    ISSN: 1434-193X
    Keywords: Fluorescent dyes ; Perylenes ; Heterocycles ; NIR dyes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Core-extended perylenetetracarboxylic bisimides were prepared by Diels-Alder reaction followed by reduction, or by nitration followed by cyclisation. Highly fluorescent dyes were obtained with absorption regions from the visible to the NIR. Applications for solar energy harvesting, and quantum counters were suggested.
    Additional Material: 9 Ill.
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  • 59
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    Electronic Resource
    Photoaddition of Aliphatic Ethers to 4-Methyl-1,2,4-triazoline-3,5-dione: Application to the Synthesis of Functionalized Crown Ethers and Mechanism (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 617-626 
    Details
    ISSN: 1434-193X
    Keywords: Radicals ; Photochemistry ; Aliphatic ethers ; Hydrogen abstraction ; Urazolyl radical ; α-Alkoxy-alkyl radical ; Diones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The photoaddition of 4-methyl-1,2,4-triazoline-3,5-dione (4-MTAD) with a wide variety of acyclic, cyclic and crown aliphatic ethers has been investigated. Monochromatic (λ = 514.5 nm) or polychromatic (λ ≥ 310 nm) irradiations give identical mono-urazolyl ethers as reaction products. Unsymmetrical acyclic ethers afford a mixture of the two α and α′ mono-urazolyl ethers. In the case of 12-crown-4, mono and di-substituted products are obtained. ESR experiments and quantum calculations at the AM1 and 6-31G* levels were performed and a possible reaction mechanism is proposed in which the most probable photochemical process is the H-abstraction leading to a urazolyl radical.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/099269_s.pdf or from the author.
    Additional Material: 3 Ill.
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  • 60
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    Electronic Resource
    Photoinduced Electron Transfer (PET) Promoted Oxidative Activation of 1-(N-Benzyl-N-methylglycyl)-(S)-prolinol: Development of Novel Strategies Towards Enantioselective Syntheses of α-Amino Acids, Their N-Methyl Derivatives and α-Hydroxy Acids Employing (S)-Prolinol as aRecyclable Chiral Auxiliary (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 657-664 
    Details
    ISSN: 1434-193X
    Keywords: Photoinduced electron transfer ; Enantioselective syntheses ; Amino acids ; α-Hydroxy acids ; (S)-Prolinol ; Recyclable chiral auxiliary ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---PET activation of 1-(N-benzyl-N-methylglycyl)-(S)-prolinol (1) in dry acetonitrile, utilizing 1,4-dicyanonaphthalene (DCN) as a light-harvesting electron-acceptor and methyl viologen (MV++) as an electron-transfer mediator, leads to the formation of 3-[benzyl(methyl)amino]perhydropyrrolo[2,1-c][1,4]oxazin-4-one (3). When this photolysis is carried out in aqueous acetonitrile, exclusively 3-hydroxyperhydropyrrolo[2,1-c][1,4]oxazin-4-one (4) is produced. The formation of 3 can be rationalized in terms of intramolecular cyclization of the in situ generated iminium cation intermediate (2) by the OH moiety of (S)-prolinol, while 4 is generated by hydrolysis of 2 followed by acetalization. Nucleophilic alkylation of 3 and 4, using Grignard reagents and allyltrimethylsilane/TiCl4, provides 12a-d & 15 and 17a-c & 21, respectively, in a highly stereoselective manner. Hydrolysis of the resultant amides (12, 15, 17, and 21) provides α-amino acid derivatives (14) and α-hydroxy acids, respectively, in optically active form, along with the recovered (S)-prolinol chiral auxiliary in its recyclable form.
    Additional Material: 1 Ill.
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  • 61
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    Electronic Resource
    New Tetrathiafulvalene-π-Spacer-Acceptor Derivatives: Synthesis, Crystal Structure, Optical and Electrochemical Properties (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 737-741 
    Details
    ISSN: 1434-193X
    Keywords: Tetrathiafulvalenes ; Charge transfer ; UV/Vis spectroscopy ; Cyclic voltammetry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---4-[2-tetrathiafulvalenyl-ethenyl]pyridine (1) has been prepared from a Wittig reaction between formyltetrathiafulvalene and 4-picolyltriphenylphosphonium chloride hydrochloride. Conversion of the pyridine moiety of 1 by reaction with methyl iodide leads to 4-[2-tetrathiafulvalenyl-ethenyl]-1-methylpyridinium iodide (2a). Neutralization of 1 with a large excess of L-tartaric acid affords 4-[2-tetrathiafulvalenyl-ethenyl]-1-methylpyridinium hydrogen tartrate (3). These TTF-π-spacer-acceptor compounds have been characterized by elemental analysis, and IR and 1H NMR spectroscopy. The crystal structure of 2a has been determined by X-ray diffraction. The cation is essentially planar. Examination of the bond lengths in 2a, UV/Vis spectra and CV data, and calculations indicate that an intramolecular charge transfer occurs in the studied compounds, although it is rather limited, and larger in 2a and 3 than in 1.
    Additional Material: 3 Ill.
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  • 62
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    Electronic Resource
    Synthesis of Silaproline, a New Proline Surrogate (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 807-811 
    Details
    ISSN: 1434-193X
    Keywords: Proline analogues ; Asymmetric synthesis ; Schöllkopf's method ; Silicon ; Amino acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The asymmetric synthesis of a new proline surrogate, incorporating the dimethylsilyl group at position 4 of proline using Schöllkopf's bis-lactim ether method, is described.
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  • 63
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    Electronic Resource
    Kinetics of Photochemical Reactions of Thionine with Thiourea (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1345-1351 
    Details
    ISSN: 1434-193X
    Keywords: Kinetics ; Photochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photochemical reaction of thionine (Th) with an organic reductant such as thioureas was studied in absolute methanol at constant temperature 25±0.1°C. Spectrophotometric methods were adopted for the determination of the values of absorbances in the presence of extremely dissociated, undissociated and partially dissociated acridine in absolute methanol. The acidity of the reaction solution H0 was controlled by using acetate buffer solutions. The effect of variables like concentration of thiourea, acidity and temperature on quantum yield (φ) was studied and the results were interpreted in terms of reaction mechanism. It was found that the quantum yield of the reactions of thionine with thiourea is controlled by two equilibria between (i) triplet state of thionine with proton and protonated triplet state of thionine, and (ii) protonated triplet state of thionine with reductant and associated complex (Th·H2T++·AH2).
    Additional Material: 5 Ill.
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  • 64
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    Electronic Resource
    Synthesis of 5-Methylbenzo[b]thieno[2,3-c]isoquinolines and5-Methylbenzo[b]seleno[2,3-c]isoquinolines (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1353-1357 
    Details
    ISSN: 1434-193X
    Keywords: Heterocycles ; Rearrangements ; C-C coupling ; C-C coupling ; Cyclizations ; Isoquinolines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -5-Methylbenzo[b]thieno[2,3-c]isoquinolines and 5-methylbenzo[b]seleno[2,3-c]isoquinolines 11b,c have been prepared by Bischler-Napieralski cyclization of 2-acetamido-3-phenylbenzo[b]heteroarenes.
    Additional Material: 4 Tab.
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  • 65
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    Electronic Resource
    An Unprecedented CoII-Tetraphenylporphyrin-Catalyzed Decomposition of Bicyclic Endoperoxides: A New Approach to Substituted Furofuran Systems (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1359-1363 
    Details
    ISSN: 1434-193X
    Keywords: Endoperoxides ; Cycloheptatriene ; Dichloroketene ; Singlet oxygen ; Cobalt ; Porphyrins ; Furans ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -CoII-tetraphenylporphyrin-catalyzed decomposition of bicyclic endoperoxides 4 and 5 with a strained double bond moiety has been studied. Compounds 4 and 5 have been synthesized by photooxygenation of 3 which itself was obtained by dichloroketene addition to cycloheptatriene, followed by removal of the chlorine atoms. An unusual decomposition mode of 4 promoted by CoII-TPP resulted in the formation of 8 and 9 which are important building blocks in furofuran systems.
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  • 66
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    Electronic Resource
    Addition of Grignard Reagents to Chiral 1,2-Bisimines: A DiasteroselectivePreparation of Unsymmetrical 1,2-Diamines (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1373-1373 
    Details
    ISSN: 1434-193X
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -No Abstract.
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  • 67
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    Electronic Resource
    Atropisomeric Transition State Analogs (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1365-1372 
    Details
    ISSN: 1434-193X
    Keywords: Atropisomerism ; Transition states ; Enzyme inhibitors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Transition state mimicry is one of the most powerful concepts in enzyme inhibitor design and has led to the development of catalytic antibodies. Transition state analogs are compounds with a fixed shape that resemble the geometry and charge distribution of the transition state of a given reaction. Stabilization of a transition state like conformation is most often achieved by incorporating a ring system into the analog. We show herein that atropisomerism can be used as a new principle for enforcing a transition state like conformation. Atropisomerism relates to the existence of stereoisomers of structurally constrained molecules due to a frozen rotation about a single bond, as for example in binaphthol. The 1-aminomethylnaphthalene derivative 1 exhibits atropisomerism due to a frozen rotation about the C(1)-C(methylene) single bond, which holds the dihedral angle θ[C(2)-C(1)-C(methylene)-N] close to 90°. Compound 1 mimics the transition state for hydride transfer between 1,4-dihydroquinolines 4 and acetone.
    Additional Material: 5 Ill.
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  • 68
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    Synthesis and Characterization of New Enantiopure 7,7′-Disubstituted 2,2′-Dihydroxy-1,1′-binaphthyls: Useful Ligands for the Asymmetric Allylation Reaction of Aldehydes (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1375-1375 
    Details
    ISSN: 1434-193X
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -No Abstract.
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  • 69
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    Electronic Resource
    Naphthocyclobutenes and Benzodicyclobutadienes: Synthesis in the Solid State and Anomalies in the Bond Lengths (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1377-1386 
    Details
    ISSN: 1434-193X
    Keywords: Diallenes ; Solid-state reactions ; Naphthocyclobutenes ; Benzodicyclobutadiene ; Through-bond interactions ; X-ray analysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The title four-membered ring compounds, naphthocyclobutenes and benzodicyclobutadienes, were produced by thermal cyclization reaction of crystalline 1,2-diallenylbenzenes and 1,6-diethynyldiallenes, respectively. These solid-state reactions proceeded efficiently and stereoselectively. The naphthocyclobutenes were shown to have extremely long C(sp3)-C(sp3) bonds (1.720-1.733 Å). The benzodicyclobutadienes were also shown to have extremely long C(sp2)-C(sp2) bonds (1.540 Å).
    Additional Material: 4 Ill.
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  • 70
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    Electronic Resource
    Synthesis of 2-Fluoro Analogues of Frontalin (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1387-1389 
    Details
    ISSN: 1434-193X
    Keywords: Natural products ; Epoxidations ; Asymmetric synthesis ; Fluorine ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The synthesis of enantiomerically and diastereomerically pure (-)-(1R,2R,5R)- and (-)-(1R,2S,5R)-2-fluoro frontalin (7) starting from (+)-(1S)-menthyl-(R)-toluene-4-sulfinate, methylmagnesium bromide, methyl fluoroacetate, 4-pentenyl bromide and diazomethane is described. The absolute stereochemistry was unambiguously determined by X-ray analysis of (+)-(1S,2R,5S,RS)-5, an intermediate in the synthesis of the enantiomeric (+)-(1S,2R,5S)-2-fluoro frontalin (7).
    Additional Material: 2 Ill.
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  • 71
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    Electronic Resource
    Synthesis of 15N-Labelled D-Isovaline and α-Aminoisobutyric Acid (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 857-859 
    Details
    ISSN: 1434-193X
    Keywords: α,α-Dialkylated amino acids ; Isotopic labeling ; Strecker synthesis ; Solvent effects ; Stereoselective hydrolysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---[15N]-D-isovaline was prepared from DL-[α-15N]-α-aminoisovaleramide by enzymatic resolution with Mycobacterium neoaurum. The 15N-isotope was introduced during the Strecker synthesis of its precursor, e.g. aminoisovaleronitrile. Attempts to prepare the amino nitrile precursor of [15N]-α-aminoisobutyric acid (Aib) led to a poor yield and loss of the label. Significantly, improved results were obtained when a cosolvent is present during formation of aminoisobutyronitrile.
    Additional Material: 1 Ill.
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  • 72
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    A General Approach to Indolizidine Alkaloids From 1-Benzyloxy-5-(p-toluenesulfonamido)-3-alken-2-ols: Synthesis of (+)-Monomorine I (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 867-867 
    Details
    ISSN: 1434-193X
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No Abstract.
    Type of Medium: Electronic Resource
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  • 73
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    Electronic Resource
    Synthesis of Highly Functionalised Carbohydrate-Derived Spiroacetals by Ring-Closing Metathesis and Pauson-Khand Reaction of Ketoglycosidic Enynes (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 873-877 
    Details
    ISSN: 1434-193X
    Keywords: Spiro compounds ; Ring-closing metathesis ; Pauson-Khand reaction ; Carbohydrates ; Enynes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The synthesis of the ketoglycosidic enynes 5, 7 and 8 starting from 2,3,4,6-tetra-O-benzyl-D-glucopyranolactone (2) is described. These enynes are subjected to ruthenium-mediated ring-closing metathesis and Pauson-Khand cyclisation to afford the highly functionalised carbohydrate spiroacetals 9 and 11-14.
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  • 74
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    Electronic Resource
    Formaldehyde SAMP-Hydrazone as a Neutral Formyl Anion Equivalent: Asymmetric Synthesis of Substituted β-Formyl δ-Lactones and Furofuran Lactones (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 893-901 
    Details
    ISSN: 1434-193X
    Keywords: Asymmetric synthesis ; Nucleophilic formylation ; Addition reactions ; Lactones ; Formyl anion equivalent ; Domino reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---An efficient asymmetric synthesis of α-substituted β-formyl δ-lactones 5 (de ≥ 98%, ee = 80-95%) and 4-substituted furofuran lactones 6 (de ≥ 98%, ee = 80-〉98%) in acceptable overall yields is reported. Key steps of the new procedure are an asymmetric Michael addition of formaldehyde SAMP-hydrazone (1) to 5,6-dihydro-2H-pyran-2-one (2) under neutral conditions, followed by trans-selective α-alkylation and subsequent cleavage of the auxiliary by ozonolysis or a hydrolytic domino reaction protocol, respectively. The absolute configurations given for the title compounds are based on three X-ray structure analyses and NOE measurements.
    Additional Material: 3 Ill.
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  • 75
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    Apicularen A and B, Cytotoxic 10-Membered Lactones with a Novel Mechanism of Action from Chondromyces Species (Myxobacteria): Isolation, Structure Elucidation, and Biosynthesis (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 913-919 
    Details
    ISSN: 1434-193X
    Keywords: Myxobacteria ; Antibiotics ; Cytotoxic ; Structure elucidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A novel highly cytotoxic metabolite, apicularen A (1), was isolated in a screening of the myxobacterial genus Chondromyces. The structure of 1 is characterized by a salicylic acid residue as part of a 10-membered lactone, which bears an acylenamine side chain. Compound 1 is an inhibitor of the proliferation of human cancer cell lines and induces apoptosis. Apicularen A (1) is present in nearly every strain of C. apiculatus, C. pediculatus, C. lanuginosus and C. robustus. Habitually 1 is accompanied by different amounts of a more polar variant, apicularen B (2), which was identified as 11-O-(2-N-acetamido-2-deoxy-β-D-glucopyranosyl)apicularen. According to feeding experiments with 13C-labeled acetates, glycine, and methionine, apicularen A (1) is an acetate-derived polyketide containing a glycine residue as precursor of the enamine. Uncommonly, the C3 starter unit is not assembled from propionate but from acetate and methionine.
    Additional Material: 6 Ill.
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  • 76
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    Oxidative Heterocyclization of 2-Alkynylbenzaldehydes with 1,2-Phenylenediamine (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1433-1441 
    Details
    ISSN: 1434-193X
    Keywords: Alkynes ; Annelation reactions ; Carbonyl compounds ; Heterocycles ; Polycycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Upon condensation of ortho-phenylenediamine (2) with ortho-alkynylbenzaldehydes in nitrobenzene, oxidative cyclizations are observed, which result in benzimidazo[2,1-a]isoquinolines (8) or isoindolo[2,1-a]quinoxalines (9) depending on the influence of additional substituents at the alkyne.
    Additional Material: 1 Ill.
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  • 77
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    N-Monoalkylation of α-Amino Acid Esters under Solid-Liquid PTC Conditions (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1443-1449 
    Details
    ISSN: 1434-193X
    Keywords: Amino acids ; Alkylations ; Phase-transfer catalysis ; Asymmetric synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---N-(2-Nitrophenylsulfonyl)- (o-NBS-AA-OMe, 4) and N-(4-Nitrophenylsulfonyl)-α-amino acid methyl esters (p-NBS-AA-OMe, 5) were N-alkylated with a variety of alkyl halides 6 under solid-liquid phase-transfer catalysis (SL-PTC) conditions, affording the alkylated products o-NBS-N-R2-AA-OMe 7 and p-NBS-N-R2-AA-OMe 8 in excellent yields without any detectable racemization.
    Additional Material: 3 Tab.
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  • 78
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    Electronic Resource
    Structure and Biosynthesis of Mutolide, a Novel Macrolide from a UV Mutant of the Fungus F-24′707 (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1451-1456 
    Details
    ISSN: 1434-193X
    Keywords: Mutolide ; Metabolites, secondary ; Macrolide ; Chemical screening ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The 14-membered macrolide, mutolide (1), was discovered by chemical screening of the culture broth of the fungus F-24′707y, obtained after UV mutagenesis of the wild type strain, which normally produces the spirobisnaphthalene cladospirone bisepoxide (2). The structure of 1 was established by detailed spectroscopic analysis, X-ray analysis and derivatisation. The biogenetic origin of the carbon skeleton and the hydroxy groups was verified by feeding sodium [1-13C]acetate and 18O2 to growing cultures of the fungus. Macrolide 1 is generated from acetate/malonate only. The unexpected change of the normal metabolite pattern of this strain is discussed, and proves the value of the OSMAC method.
    Additional Material: 2 Ill.
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  • 79
    Electronic Resource
    Electronic Resource
    A Method for the Conversion of Sulfoximines to Sulfones: Application to Polymer-Bound Sulfoximines and to the Synthesis of Chiral Sulfones (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1457-1465 
    Details
    ISSN: 1434-193X
    Keywords: Sulfoximines ; Oxidative cleavage ; Sulfones ; Polymer-bound sulfoximines ; Solid-phase synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Reaction of N-alkyl, N-aryl, and N-H sulfoximines with m-chloroperbenzoic acid cleanly gives the corresponding sulfones in high yield. In the case of the cleavage of N-alkyl and N-arylsulfoximines, formation of the corresponding nitroso compounds as the other reaction product was proven. Starting from enantio- and diastereopure sulfoximines, a number of chiral sulfones, including the axially chiral sulfone 6 and the sulfonyl-functionalized homoallylic alcohol 8, have been prepared. Reaction of the enantiopure sulfoximine 30 with Merrifield resin gave the polymer-bound sulfoximine 32. Oxidative cleavage of 32 afforded the sulfone 16 in high yield. Deprotonation of the sulfoximine resin 32 and reaction of Li-32 with benzaldehyde and propanal furnished the β-hydroxysulfoximine resins 33a and 33b, respectively. Oxidative cleavage of 33a and 33b readily afforded the β-hydroxy sulfones 14a and 14b, respectively.
    Additional Material: 1 Ill.
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  • 80
    Electronic Resource
    Electronic Resource
    Base- and Sugar-Modified Cytidine Monophosphate N-Acetylneuraminic Acid (CMP-Neu5Ac) Analogues - Synthesis and Studies with α(2-6)-Sialyltransferase from Rat Liver (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1467-1482 
    Details
    ISSN: 1434-193X
    Keywords: Glycosyl phosphates ; Nucleosidephosphate sugars ; Neuraminic acid ; Glycosyltransferase ; Carbohydrates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The reaction of sialyl phosphites 1, 22a-d, 28, 39, and 45 with acyl-protected riboside 5-phosphorous acids 2a,b and 23 directly furnished, without addition of a catalyst, under phosphite/phosphate exchange the corresponding β-configured sialyl riboside monophosphates 3a,b, 24a-d, 29, 46, and 47. The synthesis of the starting materials, formation of the products, and their treatment with sodium methanolate in methanol and subsequent hydrolysis of the sialic acid ester moiety to provide the unprotected target molecules 4a,b, 25a-d, 30, 48, and 49 is described. Investigations with α(2-6)-sialyltransferase from rat liver showed that base replacement in CMP-Neu5Ac (4a,b) is not tolerated by the enzyme but that modifications of the 5-, 8-, or 9-position of the neuraminic acid residue (25a-d, 30, 48, 49) are tolerated.
    Additional Material: 1 Tab.
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  • 81
    Electronic Resource
    Electronic Resource
    Inter- and Intramolecular Crotyltitanation of Acetals: A Novel and Effective Route to Three- to Five-Membered Vinylcycloalkanes and Bicyclic Fused Compounds (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1483-1488 
    Details
    ISSN: 1434-193X
    Keywords: Titanium ; Acetals ; Cyclizations ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---η3-Crotyltitanocenes react with acetals to produce homoallylic ethers. The intramolecular coupling involving tethered dienyl acetals provides a convenient access to vinylcycloalkanes and bicyclic fused compounds. This new cyclization reaction proceeds with a total regioselectivity in the exo fashion, and with good to excellent diastereoselectivity depending especially on the tether chain length.
    Additional Material: 3 Tab.
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  • 82
    Electronic Resource
    Electronic Resource
    Stereoselective Azepine-Ring Formation Through Ene Reactions of 3-(Alk-2-enyl)amino-2-cyanoacrolein Derivatives (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1489-1496 
    Details
    ISSN: 1434-193X
    Keywords: Ene reactions ; Azepines ; Aminoacroleins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The reaction of 3-[N-(alk-2-enyl)benzylamino]-2-cyanoacroleins 9 with primary amines 12 and 13 gave 4,5-dihydro-1H-azepines 14 and 15 stereoselectively, through an intramolecular ene reaction of the imine derivatives of 9. Similarly, carbonyl-ene reaction of acrolein derivatives 9, and olefin-ene reaction of their conjugated diene compounds 22, and 24-27 are also discussed. These ene reactions established an efficient synthetic approach toward monocyclic azepine ring formation.
    Additional Material: 1 Ill.
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  • 83
    Electronic Resource
    Electronic Resource
    A Convenient Synthesis of 2,2-Diallylated Nitrogen Heterocycles by Allylboration of Lactams (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1503-1505 
    Details
    ISSN: 1434-193X
    Keywords: Lactams ; Reductions ; Boranes ; Nitrogen heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Lactams containing an N-H bond are smoothly transformed into 2,2-diallylated nitrogen heterocycles on heating with allylic boranes in THF followed by deboronation
    Additional Material: 1 Tab.
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  • 84
    Electronic Resource
    Electronic Resource
    Pyridyl and Furyl Epoxides of More Than 99% Enantiomeric Purities: The Use of a Phosphazene Base (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1077-1080 
    Details
    ISSN: 1434-193X
    Keywords: Asymmetric synthesis ; Phosphazene base ; Pyridyl epoxide ; Furyl epoxide ; Pyridyl alcohol ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---trans-1-(2-Pyridyl)-, trans-1-(3-pyridyl)-, trans-1(2-furyl)-, and trans-1(3-furyl)-2-phenyl epoxides with enantiomeric purities ranging from 96.8 to 99.8% [in favor of the (+, EtOH)-isomer] are obtained in two steps from pure (R,R,R)-oxathiane which is recovered (85-90%) and reused. The chiral bidentate ligand 2-phenyl-(S)-1-(2-pyridyl)ethanol with 99.6% ee was obtained in three steps and 67% overall isolated yield.
    Additional Material: 1 Ill.
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  • 85
    Electronic Resource
    Electronic Resource
    Solid State and Solution Conformation of 6-[4-[N-tert-ButoxycarbonylN-(N′-ethyl)propanamide]imidazolyl]-6-deoxycyclomaltoheptaose: Evidence of Self-Inclusion of the Boc Group within the β-Cyclodextrin Cavity (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1065-1076 
    Details
    ISSN: 1434-193X
    Keywords: Cyclodextrins ; Inclusion compounds ; Carcinine ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A new modified β-cyclodextrin (β-CD) derivative 1 that was functionalized in position 6 with Boc-Carcinine was synthesised and its crystal structure was determined. The structure reveals a “sleeping swan”-like shape, the covalently bonded Boc-Carcinine moiety forming a folded structure with the Boc group inserted within the hydrophobic cavity of the β-cyclodextrin. The conformation of the Carcinine moiety is determined by the inclusion of the Boc group and is further stabilised by three intramolecular hydrogen bonds, two between the amide N1-H group, the carbonyl C′1=O1 group and a primary hydroxylic group of the glucose unit 5, one between the carbonyl C′0=O0 group and the primary hydroxylic group of the glucose unit 2. The β-CD macrocycle differs only slightly from unmodified β-CDs, maintaining an approximate sevenfold symmetry. The solution structure of the new β-CD derivative was investigated by NMR spectroscopy and circular dichroism (c.d.) spectroscopy. In addition to a complete (1H and 13C) assignment of the pendant Boc-Carcinine group, the NMR study allowed the assignment of all the proton resonances associated with the β-CD macrocycle. Furthermore, NMR and c.d. results indicated that the self-inclusion of the Boc group within the β-CD cavity is retained in aqueous solution. In order to estimate the strength of this self-inclusion complex a series of competition experiments with the external guest 1-adamantanol was carried out using c.d. spectroscopy.
    Additional Material: 9 Ill.
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  • 86
    Electronic Resource
    Electronic Resource
    1,2,3,4-Tetra-tert-butyl-4-trimethylsilyl-4-sila-2-cyclobuten-1-yl: A Quantum Mechanical and ESR Study (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1107-1112 
    Details
    ISSN: 1434-193X
    Keywords: Photochemistry ; Radicals ; EPR spectroscopy ; Quantum mechanical calculations ; Silicon compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Trisilane 7 has been synthesized as a potential photochemical precursor of tetra-tert-butylsilatetrahedrane (5) and/or tetra-tert-butylsilacyclobutadiene (6). Astonishingly, only one Si,Si bond is broken upon irradiation of 7 and the silacyclobutenyl radical 9 can be identified as the reaction product. The structure of radical 9, which in the absence of oxygen is persistent even at room temperature, has been elucidated by comparison of its experimental and calculated ESR spectra.
    Additional Material: 2 Ill.
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  • 87
    Electronic Resource
    Electronic Resource
    Chiral Ruthenium-Catalyzed Hydrogenation of β-Keto Sulfoxides (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1535-1537 
    Details
    ISSN: 1434-193X
    Keywords: Catalytic hydrogenation ; Ruthenium complexes ; Sulfoxides ; Sulfoxides ; Asymmetric induction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The diastereoselective catalytic hydrogenation of β-keto sulfoxides in the presence of ruthenium complexes was studied. Optically pure β-keto sulfoxides were hydrogenated in the presence of achiral catalysts leading to moderate yields and stereoselectivities. Using chiral ruthenium catalysts such as [(R)-MeO-BIPHEPRuBr2] and [(S)-MeO-BIPHEPRuBr2], the hydrogenation proceeded in good yields with very high diastereoselectivity. Chirality at the secondary centre of the β-hydroxy sulfoxides produced was controlled by the catalysts.
    Additional Material: 2 Ill.
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  • 88
    Electronic Resource
    Electronic Resource
    Synthesis and Metal Ion Complexation Studies of [60]Fullerene Derivatives of Tetrathiafulvalene Crown Ethers (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1157-1163 
    Details
    ISSN: 1434-193X
    Keywords: Supramolecular chemistry ; Fullerenes ; Crown compounds ; Electrochemistry ; Metal complexation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The synthesis of two novel [60]fullerene derivatives containing the electron donor tetrathiafulvalene and metal-complexing crown ethers is described, and their complexation ability with alkali metal cations is studied by solid-liquid extraction techniques, cyclic voltammetry and 1H NMR spectroscopy.
    Additional Material: 4 Ill.
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  • 89
    Electronic Resource
    Electronic Resource
    Chiral Atropisomeric Metalloporphyrins in the Enantioselective Styrene Epoxidation (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1165-1171 
    Details
    ISSN: 1434-193X
    Keywords: Porphyrinoids ; Asymmetric catalysis ; Atropisomerism ; Epoxidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A new series of porphyrins has been synthesised, incorporating four identical chiral binaphthyl derivatives in the meso-positions. Owing to a hindered rotation around the bond between the naphthyl and the porphyrin, four atropisomers are generated, which were fully separated by preparative TLC and thoroughly characterised. The free bases were metallated with iron(III) and manganese(III) and the resulting complexes were used as catalytic precursors in styrene epoxidation. The reactions show chemoselectivity and enantioselectivity, depending on the stereochemistry of the metalloporphyrin. It is demonstrated that highest efficiency is performed by the ααββ isomer, showing C2 symmetry.
    Additional Material: 4 Ill.
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  • 90
    Electronic Resource
    Electronic Resource
    1,3-Dioxycyclopentadienes from (1-Alkynyl)carbene Tungsten Complexes - Domino Cyclization/Cycloaddition Reactions (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1183-1192 
    Details
    ISSN: 1434-193X
    Keywords: Carbene complexes ; 1-Metallahexatrienes ; Cyclopentadienes ; Carbene complexes ; Tungsten ; Domino cyclization ; Pentalenes ; Spirocyclopentanes ; Spiro compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -1,3-Dioxytetrahydropentalenes 9 have been generated by base-catalyzed addition of protic oxygen nucleophiles ROH 6a-g (RO = carboxy or phenyloxy) to the [2-(1-cyclopentenyl)ethynyl]carbene tungsten complex 3. Compounds 9 are highly reactive and afford (cyclobutenyl)carbene complexes 12a-g through spontaneous [2+2] cycloaddition to a second molecule of the (1-alkynyl)carbene complex 3. Thermolysis of compounds 12 was found to generate indeno[b]-spiro-tricyclo[5.3.0.0]decadienes 18 through π-cyclization of the 1-tungsta-1,3,5-hexatriene unit involving insertion of carbon monoxide into the W—C bond.
    Additional Material: 3 Ill.
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  • 91
    Electronic Resource
    Electronic Resource
    Synthesis and Light-Harvesting Properties of Niphaphyrins (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1193-1197 
    Details
    ISSN: 1434-193X
    Keywords: Porphyrinoids ; Light-harvesting structures ; Energy transfer ; Nanostructures ; Photochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The synthesis of niphaphyrins, a new class of rigid, snowflake-shaped porphyrin hexamers designed to mimic the light-harvesting antenna complexes of photosynthetic purple bacteria, is described. In these D6- or D3-symmetric assemblies, six porphyrin macrocycles, as free bases or as zinc chelates, are covalently attached to the six positions of a benzene core through rigid ethynyl linkers. A very efficient singlet excited-state energy transfer has been observed from the Zn chelates to the free-base porphyrin (Fb) chromophores in a niphaphyrin in which three zinc porphyrin chelates alternate with three porphyrin free bases. The overall yield of energy transfer (ΦET) has been estimated as 98%.
    Additional Material: 2 Ill.
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  • 92
    Electronic Resource
    Electronic Resource
    Synthesis of α- and β-Substituted Aminoethane Sulfonamide Arginine-Glycine Mimics (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1219-1228 
    Details
    ISSN: 1434-193X
    Keywords: Peptidomimetics ; Peptidosulfonamides ; Peptidomimetics ; Transition-state isosteres ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -In this paper we present a synthesis of both α- and β-substituted aminoethane sulfonamide arginine mimics. The α-substituted sulfonamides were obtained starting from an alkene, whereas the β-substituted sulfonamides were derived from an amino acid derivative.
    Additional Material: 1 Ill.
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  • 93
    Electronic Resource
    Electronic Resource
    Nucleophilic Additions of Sodium Alkoxides to 4,4-Dichloro-1,1-diphenyl-2-azabuta-1,3-diene (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1235-1239 
    Details
    ISSN: 1434-193X
    Keywords: Nucleophilic additions ; Nucleophilic substitutions ; Azabutadienes ; Δ2-Oxazoline ; Azabutenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The reaction of some sodium alkoxides with 4,4-dichloro-1,1-diphenyl-2-azabuta-1,3-diene is described. Whereas sodium methoxide, ethoxide or isopropoxide leads to 1,3-bis(alkoxy)- and/or 1,3,4-tris(alkoxy)-2-azabut-2-enes, the sodium salt of ethyl glycolate gives a Δ2-oxazoline. Mechanisms for the formation of these products are proposed.
    Additional Material: 3 Ill.
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  • 94
    Electronic Resource
    Electronic Resource
    Ring Expansion vs. Cleavage of the Exocyclic Double Bond of 2-Cycloalkylidenedihydrobenzothiazoles and -benzimidazoles by Methanesulfonyl Azide (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1229-1233 
    Details
    ISSN: 1434-193X
    Keywords: Azides ; Cleavage reactions ; Cycloadditions ; Nitrogen heterocycles ; Ring expansion ; Sulfur heterocycles ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Deprotonation of the 2-cycloalkylbenzothiazolium perchlorates 1f-h with sodium hydride in the presence of methanesulfonyl azide (3) affords the spirocyclic dihydro-1,4-benzothiazines 9f-h together with small amounts of the 2-iminobenzothiazole 5. The 2-cycloalkylidenedihydrobenzimidazoles 11e-h are generated by deprotonation with potassium hydride from the corresponding 2-cycloalkylbenzimidazolium salts 10e-h, and trapped with 3 to yield the zwitterions 12e-h. Whereas 12h is thermally unstable, 12e-g are isolated and thermolysed at 20-80 °C. The cyclopropyl zwitterion 12e decomposes in an ill-defined way, only at temperatures above 80 °C. In contrast, 12f,g, and, in particular, 12h, decompose more readily to furnish the products of ring expansion (13f-h) and those of a [3 + 2] cycloreversion (6 and 14) of intermediate spirocyclic triazolines. Products that might be indicative of the intervention of hypothetical zwitterions of type 8 cannot be detected.
    Additional Material: 4 Tab.
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  • 95
    Electronic Resource
    Electronic Resource
    Modifications of Peptides by Chelate Claisen Rearrangements of Manganese Enolates (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1241-1251 
    Details
    ISSN: 1434-193X
    Keywords: Amino acids ; Enolates ; Rearrangements ; Metal complexes ; Peptides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Deprotonation of allylic esters of peptides at -70 °C in the presence of metal salts results in the formation of metal peptide enolate complexes, which undergo Claisen rearrangement on warming to room temperature to produce stereoselectively modified peptides. By far the best results are obtained with manganese enolates. With these enolates, the amino acids incorporated in the peptide chain have no significant influence on the rearrangement, neither on the yield nor on the stereochemical outcome. Therefore, this protocol is extremely suitable for the stereoselective modification of peptides by using esters of chiral allylic alcohols. α-Alkylated amino acids can be incorporated into peptides as well.
    Additional Material: 2 Tab.
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  • 96
    Electronic Resource
    Electronic Resource
    Titanium(III) Compounds with η2-Pyrazolato Ligands (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 13-16 
    Details
    ISSN: 1434-1948
    Keywords: Pyrazole ; Titanium ; Redox reaction ; Mercury ; Amalgams ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reduction of [L2TiCl2] (1) (L = 3,5-tert-butylpyrazolate) with 1% Na/Hg in tetrahydrofuran (THF) affords the complex [L2TiCl(THF)2] (2), which crystallizes from hexane in moderate yield. The analogous reduction carried out in toluene gives dimeric [(L2TiCl)2] (3) in high yield. If the reduction time is extended to 3 days, the complex [L3Ti] (4) is isolated as light blue crystals in low yield. An alternative procedure for preparing compound 4 requires mixing [TiCl3(THF)3] with 3 equivalents of potassium 3,5-tert-butylpyrazolate in toluene. Crystallization from hexane affords 4 in high yield. Crystallographic data for 2, 3 and 4 are presented.
    Additional Material: 3 Ill.
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  • 97
    Electronic Resource
    Electronic Resource
    Microwave-Assisted Rapid Incorporation of Ruthenium into Lacunary Keggin-Type Polyoxotungstates: One-Step Synthesis, 99Ru, 183W NMR Characterization and Catalytic Activity of [PW11O39RuII(DMSO)]5- (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 17-20 
    Details
    ISSN: 1434-1948
    Keywords: Polyoxometalates ; Ruthenium ; Homogeneous catalysis ; Oxidations ; Microwaves ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Microwave irradiation for 15 minutes allowed the highly selective hydrothermal synthesis of the diamagnetic, air-stable oxidation catalyst [PW11O39RuII(DMSO)]5-, as confirmed by 1H, 31P, 99Ru and 183W NMR techniques.
    Additional Material: 3 Ill.
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  • 98
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    Electronic Resource
    Benzimidazole, Benzothiazole and Benzoxazole Ruthenium(II) Complexes; Catalytic Synthesis of 2,3-Dimethylfuran (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 29-32 
    Details
    ISSN: 1434-1948
    Keywords: Arene complexes ; Ruthenium ; Benzimidazole ; Benzothiazole ; Benzoxazole ; Cycloisomerisation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fourteen ruthenium(II) complexes of the type [RuCl2(η6-arene)L], (arene = 1,4-MeC6H4Pri or C6Me6; L = benzimidazole derivative in which the NH group is substituted by N-alkyl or isoelectronic O or S atoms) have been prepared by cleavage of [RuCl2(η6-arene)]2 with the N-heterocycle L. Their spectroscopic and electrochemical properties are described. The effect of the nature of the benzazole (L) on the catalytic activity of these complexes for the intramolecular cyclization of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran has also been studied; the benzimidazole complexes were found to be the most active.
    Additional Material: 5 Tab.
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  • 99
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    Electronic Resource
    Mononuclear Ni, Pd and Pt Complexes with ′S3′2- Thioether Thiolate and HNPnPr3 Phosphorane Imine Ligands [′S3′2- = Bis(2-mercaptophenyl)sulfide (2-)] (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 59-63 
    Details
    ISSN: 1434-1948
    Keywords: Phosphorane imine ; Sulfur ligands ; Nickel ; Palladium ; Platinum ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of the trinuclear [M(′S3′)]3 complexes {M = Ni (4), Pd (5), Pt (6); ′S3′2- = bis(2-mercaptophenyl)sulfide (2-)} with HNPnPr3 yielded the new phosphorane imine complexes [M(NHPnPr3)(′S3′)] {M = Ni (1), Pd (2), Pt (3)}. The complexes 1-3 have been completely characterized and are rare examples of mononuclear phosphorane imine complexes with late transition metals. Spectroscopic and structural results indicate that the HNPnPr3 ligands favor the ylidic structure when binding to [M(′S3′)] fragments. X-ray structure determinations showed that [M(NHPnPr3)(′S3′)] complexes associate through N-H···S(thiolate) bridges to give centrosymmetric dimers.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    Solution Equilibria in YbDOTMA, a Chiral Analogue of One of the Most Successful Contrast Agents for MRI, GdDOTA (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 75-82 
    Details
    ISSN: 1434-1948
    Keywords: Macrocyclic ligands ; Conformational equilibria ; EXSY spectroscopy ; Lanthanide-induced shifts ; Solution structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure and the conformational equilibria in aqueous and methanolic solutions of YbDOTMA (DOTMA = (1R,4R,7R,10R)-α,α′,α′′,α′′′′-tetramethyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) are investigated and the dynamics studied by means of NMR methods. The presence of two isomeric forms in slow exchange is confirmed and quantitatively characterized by EXSY. The exchange peaks are assigned to the inversion of the conformation of the macrocycle ring. No evidence is obtained of a reorientation of the methyl acetate substituents. The protons switch between positions with the same geometrical factors, i.e. positions that would have the same pseudocontact shifts were it not for the different magnetic susceptibility anisotropies of the two species; steady-state NOE spectra on the major form allow unequivocal assignment of the conformations of the two isomers.Supporting information for this article is available on the WWW under -//_/_http://www.wiley-vch.de/contents/jc_2005/2000/99141_s.pdf or from the author.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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