Search results for "Fluorenes"
showing 10 items of 25 documents
Redox-responsive organometallic foldamers from ferrocene amino acid: Solid-phase synthesis, secondary structure and mixed-valence properties
2011
Oligoferrocenes Fmoc-Fca(n)-OMe (n=3-5) are assembled in a stepwise precise manner from Fmoc-protected ferrocene amino acid Fmoc-Fca-OH (H-Fca-OH = 1-amino-1'-ferrocene carboxylic acid; Fmoc = 9-fluorenylmethyloxycarbonyl) via amide bonds on solid supports by sequential Fmoc deprotection, acid activation and coupling steps. The resulting well-defined oligomers form ordered zigzag structures in THF solution with characteristic hydrogen bonding patterns. Electrochemical experiments reveal sequential oxidations of the individual ferrocene units in these peptides giving mixed-valent cations. Optical intervalence electron transfer is detected by intervalence transitions in the near-IR.
Regioselective substitution of 6,7-dichloroquinoline-5,8-dione: synthesis and X-ray crystal structure of 4a,10,11-triazabenzo[3,2-a]fluorene-5,6-dion…
2003
6,7-Dichloroquinoline-5,8-dione (1) was reacted with a number of 2-aminopyridine derivatives. Of the several possible products of this reaction, 4a,10,11-triazabenzo[3,2-a]fluorene-5,6-dione (6), produced by condensation and rearrangement, was obtained as the major product, and its structure was subsequently unambigously determined by X-ray crystallographic study. Ortho-quinones were produced via nucleophilic substitution at position C7, which was unexpected, considering that para-quinones were produced via C6 substitution in the reaction between compound 1 and ethyl acetoacetate in our previous work. Such unexpected nucleophilic substitution at C7 provides an effective, yet simple route, t…
Modular Approach to 9-Monosubstituted Fluorene Derivatives Using Mo(V) Reagents.
2016
Oxidative coupling using molybdenum(V) reagents provides fast access to highly functionalized 9-monosubstituted fluorenes. This synthetic approach is highly modular, is high yielding, and tolerates a variety of labile moieties, e.g. amides or iodo groups. The established protocol leads to promising precursors for pharmacologically important analogues of melatonin.
The aryl hydrocarbon receptor-dependent deregulation of cell cycle control induced by polycyclic aromatic hydrocarbons in rat liver epithelial cells
2006
Disruption of cell proliferation control by polycyclic aromatic hydrocarbons (PAHs) may contribute to their carcinogenicity. We investigated role of the aryl hydrocarbon receptor (AhR) in disruption of contact inhibition in rat liver epithelial WB-F344 'stem-like' cells, induced by the weakly mutagenic benz[a]anthracene (BaA), benzo[b]fluoranthene (BbF) and by the strongly mutagenic benzo[a]pyrene (BaP). There were significant differences between the effects of BaA and BbF, and those of the strongly genotoxic BaP. Both BaA and BbF increased percentage of cells entering S-phase and cell numbers, associated with an increased expression of Cyclin A and Cyclin A/cdk2 complex activity. Their eff…
An evaluation of solid phase microextraction for aliphatic amines using derivatization with 9-fluorenylmethyl chloroformate and liquid chromatography
2005
The reliability of SPME combined with a chemical reaction for the analysis of short-chain aliphatic amines by liquid chromatography has been investigated. Different options to couple SPME and derivatization have been tested and compared: (i) derivatization of the analytes in solution followed by the extraction of the derivatives, (ii) extraction of the analytes and subsequent derivatization by immersing the SPME fibre onto a solution of the reagent, and (iii) extraction/derivatization of the analytes using fibres previously coated with the reagent. Methylamine (MA), dimethylamine (DMA) and trimethylamine (TMA) have been selected as a model of primary, secondary and tertiary amines, respecti…
New polyamine drugs as more effective antichagas agents than benznidazole in both the acute and chronic phases.
2018
Abstract Despite the continuous research effort that has been made in recent years to find ways to treat the potentially life threatening Chagas disease (CD), this remains the third most important infectious disease in Latin America. CD is an important public health problem affecting 6–7 million people. Since the need to search for new drugs for the treatment of DC persists, in this article we present a panel of new polyamines based on the tripodal structure of tris(2-aminomethyl)amine (tren) that can be prepared at low cost with high yields. Moreover, these polyamines present the characteristic of being water-soluble and resistant to the acidic pH values of stomach, which would allow their…
Clinical significance of detectable and quantifiable HCV RNA at the end of treatment with ledipasvir/sofosbuvir in GT1 patients
2018
Background & aims AASLD/IDSA treatment guidelines for hepatitis C virus (HCV) infection state that testing for quantitative HCV RNA can be considered at the end of antiviral treatment (EOT) with interferon-free regimens. However, it remains unclear how to respond to a detectable or even quantifiable HCV RNA result. The aim of this study was to analyse the frequency and predictive value of detectable and quantifiable HCV RNA results at the EOT in patients with HCV genotype 1 infection treated with ledipasvir (LDV) and sofosbuvir (SOF) ± ribavirin (RBV) in a large real-world cohort. Methods A retrospective analysis of the DHC-R (Deutsches Hepatitis C-Register, German Hepatitis C-Registry) coh…
Cockayne syndrome: varied requirement of transcription-coupled nucleotide excision repair for the removal of three structurally different adducts fro…
2014
Hereditary defects in the transcription-coupled nucleotide excision repair (TC-NER) pathway of damaged DNA cause severe neurodegenerative disease Cockayne syndrome (CS), however the origin and chemical nature of the underlying DNA damage had remained unknown. To find out, to which degree the structural properties of DNA lesions determine the extent of transcription arrest in human CS cells, we performed quantitative host cell reactivation analyses of expression vectors containing various synthetic adducts. We found that a single 3-(deoxyguanosin-N 2-yl)-2-acetylaminofluorene adduct (dG(N 2)-AAF) constitutes an unsurmountable obstacle to transcription in both CS-A and CS-B cells and is remov…
High efficacy of direct-acting anti-viral agents in hepatitis C virus-infected cirrhotic patients with successfully treated hepatocellular carcinoma
2018
Background: The efficacy of direct-acting anti-viral (DAA) therapy in patients with a history of hepatocellular carcinoma (HCC) is unknown. Aim: We prospectively evaluated whether previously treated HCC affects DAA efficacy in a large real-life cohort of cirrhotic patients. Methods: From January to December 2015 all consecutive HCV mono-infected patients with cirrhosis and/or history of HCC attending 10 Italian tertiary liver centres were enrolled. Baseline characteristics and response to therapy were recorded. 1927 patients were enrolled (mean age: 62.1 10.9 years; 1.205 males). Genotype 1 was the most frequent (67.9%) followed by genotypes 3 (12.4%), 2 (11.2%) and 4 (8.6%). 88.4% and 10.9…
Sample Preparation Improvement in Polycyclic Aromatic Hydrocarbons Determination in Olive Oils by Gel Permeation Chromatography and Liquid Chromatogr…
2005
Abstract The determination of 15 polycyclic aromatic hydrocarbons (PAHs) in olive oil samples has been improved in order to obtain a fast methodology with a low limit of detection through the combination of liquid–liquid extraction with acetonitrile and preparative gel permeation chromatography (GPC) prior to the injection of purified extracts into a C18 column. Acetonitrile–water was used as the mobile phase with a gradient from 50 to 95%, w/w, acetonitrile in 30 min. The oven temperature was maintained at 15°C, and fluorometric detection was made at a fixed excitation wavelength of 264 nm and variable, optimal emission wavelength for each analyte ranging from 352 nm for 11-H-benzo(b)fluor…