A convenient synthetic approach to bis-functionalised quaterfluorenes

Ni(COD)₂ promoted coupling of bromofluorenes functionalised with boronic esters or trimethylsilyl groups proves to be an efficient method for the preparation of reactive bifluorenes, which are key intermediates for the synthesis of bis-substituted oligofluorenes. The synthetic method has been exploited as a key step for the synthesis of a chiral 2,7?-diiodo-quaterfluorene and a 2,7?-bis-amino quaterfluorene.     

Melting behaviour of a series of diamides

The melting behaviour of diamides of general formula (n — C_pH_2p+1)CONH-(CH₂)_qNHCO(n — C_pH_2p+1) has been investigated by calorimetric, dilatometric and IR techniques. The conformational contribution to the melting entropy, calculated from the hypothesis of complete conformational freedom of the molecules at the melting point, has been compared with the experimental data. The higher melting points of the diamides, as compared with those of the linear hydrocarbons having the same number of conformationally flexible chain bonds, are attributed to a reduction of conformational freedom of the chain segments in the liquid state (caused by the large fraction of hydrogen bonds maintained in the melt).     

Iridoid and Phenylethyl Glycosides from Globularia sintenisii

A new iridoid glycoside, sintenoside ( 1 ) and two new phenylethyl glycosides, globusintenoside (=2‐(3,4‐dihydroxyphenyl)ethyl‐O‐6‐O‐feruloyl‐β‐D ‐glucopyranosyl‐(1→4)‐α‐L ‐rhamnopyranosyl‐(1→3)‐4‐O‐caffeoyl‐β‐D ‐glucopyranoside; 2 ) and 3′′′‐O‐methylcrenatoside (=1,2‐O‐[2‐(3,4‐dihydroxyphenyl)ethan‐1,2‐diyl]‐3‐O‐α‐L ‐4‐O‐feruloyl‐rhamnopyranosyl‐β‐D ‐glucopyranose; 3 ) were isolated from the underground parts of Globularia sintenisii, along with three known iridoid glycosides, lytanthosalin, globularin, catalpol, and six known phenylethyl glycosides, verbascoside, isoverbascoside, leucoscepthoside A, plantainoside C, martynoside, and isocrenatoside. The structure elucidation of the isolated compounds was performed by spectroscopic methods (MS and 1D and 2D NMR).     

First Synthesis of Racemic Trans Propargylamino-Donepezil,a Pleiotrope Agent Able to Both Inhibit AChE and MAO-B,with Potential Interest against Alzheimer’s Disease

Alzheimer’s disease (AD) is a multifactorial neurodegenerative disease towards which pleiotropic approach using Multi-Target Directed Ligands is nowadays recognized as probably convenient. Among the numerous targets which are today validated against AD, acetylcholinesterase (ACh) and Monoamine Oxidase-B (MAO-B) appear as particularly convincing, especially if displayed by a sole agent such as ladostigil, currently in clinical trial in AD. Considering these results, we wanted to take benefit of the structural analogy lying in donepezil (DPZ) and rasagiline, two indane derivatives marketed as AChE and MAO-B inhibitors, respectively, and to propose the synthesis and the preliminary in vitro biological characterization of a structural compromise between these two compounds, we called propargylaminodonepezil (PADPZ). The synthesis of racemic trans PADPZ was achieved and its biological evaluation established its inhibitory activities towards both (h)AChE (IC₅₀ = 0.4 µM) and (h)MAO-B (IC₅₀ = 6.4 µM).     

QSAR Models for Human Carcinogenicity: An Assessment Based on Oral and Inhalation Slope Factors

Carcinogenicity is a crucial endpoint for the safety assessment of chemicals and products. During the last few decades, the development of quantitative structure–activity relationship ((Q)SAR) models has gained importance for regulatory use, in combination with in vitro testing or expert-based reasoning. Several classification models can now predict both human and rat carcinogenicity, but there are few models to quantitatively assess carcinogenicity in humans. To our knowledge, slope factor (SF), a parameter describing carcinogenicity potential used especially for human risk assessment of contaminated sites, has never been modeled for both inhalation and oral exposures. In this study, we developed classification and regression models for inhalation and oral SFs using data from the Risk Assessment Information System (RAIS) and different machine learning approaches. The models performed well in classification, with accuracies for the external set of 0.76 and 0.74 for oral and inhalation exposure, respectively, and r² values of 0.57 and 0.65 in the regression models for oral and inhalation SFs in external validation. These models might therefore support regulators in (de)prioritizing substances for regulatory action and in weighing evidence in the context of chemical safety assessments. Moreover, these models are implemented on the VEGA platform and are now freely downloadable online.     

In vivo measurement of vascular modulation in experimental tumors using a fluorescent contrast agent

Abstract We compared the effectiveness of three optical techniques based on fluorescence imaging and spectroscopy with indocyanine green (ICG) contrast agent to evaluate in vivo the disruption of the active vasculature induced by a vascular targeting agent. The blood perfusion of the MDA-MB-435 tumor model transplanted in nude mice was estimated from the signal of the contrast agent measured immediately after its systemic injection in mice. Optical measurements were performed using a fluorescence imaging setup and a fiber-based time correlated single photon counting (TCSPC) apparatus. This latter apparatus was used to measure the tumor fluorescence in transmittance geometry and the change in the basal optical absorption induced by the contrast agent, thus providing an alternative estimation of the blood content in the tumor. Mice were divided into four groups. Three groups were treated with different doses of the vascular disrupting agent ZD6126, the fourth group (control group) received the drug vehicle only. Optical measurements were carried out 3 h after pharmacologic treatment. After 24 h, mice were killed, tumors were excised and the extent of necrosis was evaluated with standard histologic analysis. On fluorescence imaging ICG emission from tumors of mice treated with ZD6126 significantly was lower compared with the emission from control mice. The histologic sections also showed a significantly higher amount of necrosis in tumors of treated mice. Both these findings, which correlate with each other, indicate an effective vascular shutdown induced by the drug. However, ICG fluorescence measured with the TCSPC apparatus in transmittance geometry and the estimate of the change in optical absorption did not allow a statistically significant differentiation between treated and control groups.     

Unusual cycloartane glycosides from Astragalus eremophilus

Eleven new cycloartane-type glycosides, named eremophilosides A-K have been isolated from the aerial parts of Astragalus eremophilus. Their structures were elucidated by MS and NMR experiments and the relative configurational analysis of eremophilosides C and D was carried out on the basis of the recently reported J-based method. Additionally, the cytotoxic activity of these compounds in MCF7 and U937 cell lines was evaluated. All tested compounds, except eremophilosides B, C, and J were found to inhibit slightly the growth (controlling the cell cycle) and/or to induce death processes in U937 cell line, the most susceptible cell line. Eremophilosides A and K resulted the most effective to induce cell death, the first by necrosis while the latter by apoptosis.     

Synthesis and optical behaviour of monodispersed oligo(fluorenylidene)s

The synthesis of the first series of monodispersed oligo(fluorenylidene)s is reported. The synthetic sequence envisages as key steps the obtainment (a) of a bis-pinacolboronate fluorenylidene dimer by a Ni(cod)₂ promoted homocoupling of the suitable 7-bromo-fluorenylidene boronic ester and (b) of the bis-pinacolboronate fluorenylidene trimer and tetramer by a Ni(cod)₂ promoted coupling of a 7-bromo-fluorenylidene boronic ester with 0.5 equiv of the corresponding 2,7-dibromofluorenylidene derivative. The optical properties of the obtained oligomers were studied. In the case of OF3 the optical behaviour was compared to that of a suitably synthesized fluorenone-containing model compound.     

Unit Root Testing in Presence of a Double Threshold Process

In this paper we propose a double threshold process that generalizes the threshold autoregressive one widely known in the literature. It is characterized by a structure with two thresholds: the first regulates the switching between two autoregressive regimes; the second threshold regulates the switching between the two regimes of the stationary innovations. A testing procedure based on a Wald statistic has been given to evaluate the presence of unit roots in the process against stationarity. The asymptotic distribution of the statistic has been derived and the size and the power of the test have been evaluated through a Monte Carlo study where the proposed test is compared to two competing unit root testing procedures. The results clearly highlight the advantage obtained from the proposed test as the asymmetry of the generating process increases.     

New Models to Predict the Acute and Chronic Toxicities of Representative Species of the Main Trophic Levels of Aquatic Environments

To assess the impact of chemicals on an aquatic environment, toxicological data for three trophic levels are needed to address the chronic and acute toxicities. The use of non-testing methods, such as predictive computational models, was proposed to avoid or reduce the need for animal models and speed up the process when there are many substances to be tested. We developed predictive models for Raphidocelis subcapitata, Daphnia magna, and fish for acute and chronic toxicities. The random forest machine learning approach gave the best results. The models gave good statistical quality for all endpoints. These models are freely available for use as individual models in the VEGA platform and for prioritization in JANUS software.