Dearomatization of Pyridines: Photochemical Skeletal Enlargement for the Synthesis of 1,2-Diazepines

In this report, we developed a unified and standardized one-pot sequence that converts pyridine derivatives into 1,2-diazepines by inserting a nitrogen atom. This skeletal transformation capitalizes on the in situ generation of 1-aminopyridinium ylides, which rearrange under UV light irradiation. A thorough evaluation of the key parameters (wavelength, reaction conditions, activating agent) allowed us to elaborate on a simple, mild, and user-friendly protocol. The model reaction was extrapolated to more than 40 examples, including drug derivatives, affording unique 7-membered structures. Mechanistic evidence supports the transient presence of a diazanorcaradiene species. Finally, pertinent transformations of the products, including ring contraction reactions to form pyrazoles, were conducted and paved the way to a broad application of the developed protocol.

Remote Radical Trifluoromethylation: A Unified Approach to the Selective Synthesis of γ-Trifluoromethyl α,β-Unsaturated Carbonyl Compounds

Site-selective trifluoromethylation of silyl dienol ethers derived from α,β-unsaturated aldehydes, ketones, and amides was achieved for the first time in the remote γ position. This photoredox catalyzed process is quite general to compounds bearing many functionalities and is applicable to the late-stage functionalization of biorelevant molecules. The use of S-perfluoroalkyl sulfoximines as ·R_F radical sources enables the generalization of the reaction to other perfluoroalkyl groups (R_F = CF₂H, C₄F₉). Importantly, an unprecedented enantioselective C(sp³)-H perfluoroalkylation process is disclosed.

Hydra bioassay for the evaluation of chlordecone toxicity at environmental concentrations, alone or in complex mixtures with dechlorinated byproducts: experimental observations and modeling by experimental design

In chlordecone (CLD)-contaminated soils of the French West Indies, if microbial remediation or a physicochemical remediation process, e.g., in situ chemical reduction, is implemented, concentrations of degradation byproducts, such as hydrochlordecones, are expected to increase in the ecosystems. To study their impact in mixtures with CLD, bioassays were carried out. They consisted in evaluating the regenerative capacity of hydra polyps, from a clone whose phylogenetic analysis confirmed that it belonged to the species Hydra vulgaris Pallas, 1766. Hydra gastric sections were exposed to CLD alone or CLD plus dechlorinated byproducts (CLD-BP) for 96 h to assess regeneration. Based on chromatographic analysis, the CLD-BP mix was composed of the 5-monohydrochlordecone isomer (CAS nomenclature), four dihydrochlordecone isomers, and one trihydrochlordecone isomer representing 50%, 47%, and 3% of the total chromatographic area, respectively. A total of 18 mixtures of CLD and CLD-BP were tested. Six environmental concentrations of CLD (2.10^-4 μM to 4.10^-2 μM) and a similar range of CLD-BP were used. Results from exposures to CLD alone showed the following: (i) a significant decrease in the regenerative capacity of hydra, except at the lowest concentration (2.10^-4 μM); (ii) a concentration-independent deleterious effect. The regeneration scores obtained after the exposure to the addition of CLD-BP were not significantly different from those obtained after exposure to CLD alone. Using an experimental design, a modeling of the regeneration scores of hydra exposed to mixtures is proposed. Interpreted carefully, since they are limited to only one type of bioassay, the present results suggest that the situation in the aquatic environments should not become worse in terms of toxicity, if soil remediation programs resulting in the formation of hydrochlordecones are put in place.

Synthesis and Photophysical Characterizations of Pyrroloquinolone Photosensitizers for Singlet Oxygen Production

A series of pyrroloquinolone photosensitizers bearing different halogen substituents (Cl, Br, I) on the heterocyclic framework was studied. These structures were readily prepared through a multi-step synthetic sequence involving an oxidative protocol as an important step to access the quinolone framework. Spectroscopic characterizations and computational investigations were carried out to study the dyes before and after the oxidative step. Interestingly, the fluorescence emission was significantly reduced upon oxidation. In spite of a low photostability under UV light, the pyrroloquinolone photosensitizers proved effective to produce singlet oxygen. Higher singlet oxygen quantum yields were obtained with photosensitizers bearing halogen atoms with a higher atomic number.

Multi-scale impact of chronic exposure to environmental concentrations of chlordecone in freshwater cnidarian, Hydra circumcincta

Chlordecone (CLD) is an organochlorine pesticide widely used in the past to control pest insects in banana plantations in the French West Indies. Due to its persistence in the environment, CLD has contaminated the soils where it has been spread, as well as the waters, and is still present in them. The objective of our study was to evaluate the effects of chronic exposure to environmentally relevant CLD concentrations in an animal model, the freshwater hydra (Hydra circumcincta). In a multi-marker approach, we have studied the expression of some target stress genes, the morphology, and the asexual reproduction rates. Our data showed that exposure to low concentrations of chlordecone leads to (i) a modulation of the expression of target genes involved in oxidative stress, detoxification, and neurobiological processes, and (ii) morphological damages and asexual reproduction impairment. We have observed non-monotonic dose-response curves, which agree with endocrine-disrupting chemical effects. Thus, "U-shaped" dose-response curves were observed for SOD, GRed, Hym355, and potentially GST gene expressions; inverted "U-shaped" curves for GPx and CYP1A gene expressions and reproductive rates; and a biphasic dose-response curve for morphological damages. Therefore, in the range of environmental concentrations tested, very low concentrations of CLD can produce equally or more important deleterious effects than higher ones. Finally, to our knowledge, this study is the first one to fill the lack of knowledge concerning the effects of CLD in Hydra circumcincta and confirms that this diploblastic organism is a pertinent freshwater model in the risk assessment.

Advances and limits of two model species for ecotoxicological assessment of carbamazepine, two by-products and their mixture at environmental level in freshwater

In order to evaluate the environmental impacts associated with the presence of low-level of pharmaceuticals in waters, chronic ecotoxicity of carbamazepine (CBZ), oxcarbazepine (OxCBZ) and acridine 9-carboxylic acid (9-CAA) and their mixture was investigated using two species from different trophic levels. Innovative approaches were developed by monitoring: (i) phytometabolites in the duckweed Lemna minor L. and, (ii) alterations at the population, cellular and molecular levels on the cnidarian Hydra circumcincta Schulze 1914, to assess the effects of 14-day chronic exposure. On H. circumcincta, the approach was conducted at 19.5 °C, the optimal growth temperature, and at 23 °C, to simulate global warming impact. In L. minor, results showed alterations of the nitrogen balance and the chlorophyll indices for OxCBZ and 9-CAA separately at environmental concentrations and for the mixture of the three studied products. However, phenolic compound index deeply varied depending on pharmaceuticals and time of exposure with no specific trend. In H. circumcincta, effects on morphology, reproduction and lipid peroxidation were observed at low level of CBZ. OxCBZ impacted the total antioxidant capacity of H. circumcincta, whereas exposure to 9-CAA affected all parameters, except the reproduction rate. Finally, 14-day exposure to the mixture of the three products also slowed the reproduction rate and altered the morphology of this cnidarian. Higher damages were detected when experiments were conducted at a temperature 3.5 °C above the optimum for Hydra growth, suggesting the relevance of taking into account possible ecotoxicological consequences of global warming. Our results confirmed the necessity of selecting sensitive organisms at different trophic levels to better assess ecotoxicity of pharmaceuticals and their mixture, especially at environmental levels and facing global changes.

How to assess trace elements bioavailability for benthic organisms in lowly to moderately contaminated coastal sediments?

The bioavailability of trace elements (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Zn) in lowly to moderately contaminated coastal sediments from the Berre lagoon, France, was assessed by comparing their potentially bioavailable concentrations and bioaccumulated concentrations in the polychaete Alitta succinea. No linear correlations were observed contrarily to what is generally observed in similar works in areas with highly contaminated sediment. Correlations between trace and major elements (Fe, Ca, S, Mg, P, Al) in Alitta succinea tissues and their distribution in organism tissues show that, in such lowly to moderately contaminated sediments, biological variabilities should be considered. Normalization procedures allow to take into account these variabilities and to identify that sediment contamination is partly involved in the benthic ecosystem degradation of the Berre lagoon. Alitta succinea cannot be used as relevant bioindicator for Zn and Co bioavailability in sediment, since these elements are regulated by this organism.

Synthesis and fluorosolvatochromic properties of 1,7-annulated indoles

New push–pull indole-based fluorescent dyes have been prepared and these compounds exhibit fluorosolvatochromic properties.

Construction of enantioenriched polysubstituted hexahydropyridazines via a sequential multicatalytic process merging palladium catalysis and aminocatalysis

An efficient multicatalytic strategy for the construction of nitrogen-containing heterocycles has been reported. The powerful combination of organic and metal catalysis in a single vessel allowed the formation of enantioenriched polysubstituted cyclic 6-membered hydrazines bearing a quaternary stereocenter in good yields and selectivities.

Multi-scale biomarker evaluation of the toxicity of a commercial azo dye (Disperse Red 1) in an animal model, the freshwater cnidarian Hydra attenuata

Acute (24 h, 48 h, 72 h) and chronic (7 days) tests have been performed to evaluate the effects of the commercial azo dye Disperse Red 1 (DR1) using various biomarkers in the freshwater invertebrate Hydra attenuata. Morphological changes have been selected to calculate ecotoxicological thresholds for sublethal and lethal DR1 concentrations. A multinomial logistic model showed that the probability of each morphological stage occurrence was function of concentration, time and interaction between both. Results of oxidative balance parameter measurements (72 h and 7 days) suggest that polyps set up defense mechanisms to limit lipid peroxidation caused by DR1. DR1 exposure at hormetic concentrations induces increase of asexual reproductive rates. This result suggests (1) an impact on the fitness-related phenotypical traits and (2) trade-offs between reproduction and maintenance to allow the population to survive harsher conditions. Changes in serotonin immuno-labeling in polyps showing alterations in feeding behavior suggest that chronic DR1 exposure impaired neuronal processes related to ingesting behavior in H. attenuata. This ecotoxicity study sheds light on the possible serotonin function in Hydra model and reports for the first time that serotonin could play a significant role in feeding behavior. This study used a multi-scale biomarker approach investigating biochemical, morphological, reproductive and behavioral endpoints in Hydra attenuata. This organism is proposed for a pertinent animal model to assess ecotoxicological impact of pollutant mixtures in freshwater environment.

Stereoselective synthesis of oxazolidinonyl-fused piperidines of interest as selective muscarinic (M1) receptor agonists: a novel M1 allosteric modulator

Syntheses of (1RS,2SR,6SR)-2-alkoxymethyl-, 2-hetaryl-, and 2-(hetarylmethyl)-7-arylmethyl-4,7-diaza-9-oxabicyclo[4.3.0]nonan-8-ones, of interest as potential muscarinic M1 receptor agonists, are described. A key step in the synthesis of (1RS,2SR,6SR)-7-benzyl-6-cyclobutyl-2-methoxymethyl-4,7-diaza-9-oxabicyclo[4.3.0]nonan-8-one, was the addition of isopropenylmagnesium bromide to 2-benzyloxycarbonylamino-3-tert-butyldimethylsilyloxy-2-cyclobutylpropanal. This gave the 4-tert-butyldimethylsilyloxymethyl-4-cyclobutyl-5-isopropenyloxazolidinone with the 5-isopropenyl and 4-tert-butyldimethylsilyloxymethyl groups cis-disposed about the five-membered ring by chelation controlled addition and in situ cyclisation. This reaction was useful for a range of organometallic reagents. The hydroboration-oxidation of (4SR,5RS)-3-benzyl-4-(tert-butyldimethylsilyloxymethyl)-4-cyclobutyl-5-(1-methoxyprop-2-en-2-yl)-1,3-oxazolidin-2-one gave (4SR,5RS)-3-benzyl-4-(tert-butyldimethylsilyloxymethyl)-4-cyclobutyl-5-[(SR)-1-hydroxy-3-methoxyprop-2-yl]-1,3-oxazolidin-2-one stereoselectively. 4,7-Diaza-9-oxabicyclo[4.3.0]nonan-8-ones with substituents at C2 that could facilitate C2 deprotonation were unstable with respect to oxazolidinone ring-opening and this restricted both the synthetic approach and choice of 2-heteroaryl substituent. The bicyclic system with a 2-furyl substituent at C2 was therefore identified as an important target. The addition of 1-lithio-1-(2-furyl)ethene to 2-benzyloxycarbonylamino-3-tert-butyldimethylsilyloxy-2-cyclobutylpropanal gave (4SR,5RS)-4-tert-butyldimethylsilyloxymethyl-4-cyclobutyl-5-[1-(2-furyl)ethenyl]-1,3-oxazolidinone after chelation controlled addition and in situ cyclisation. Following oxazolidinone N-benzylation, hydroboration at 35 °C, since hydroboration at 0 °C was unexpectedly selective for the undesired isomer, followed by oxidation gave a mixture of side-chain epimeric alcohols that were separated after SEM-protection and selective desilylation. Conversion of the neopentylic alcohols into the corresponding primary amines by reductive amination, was followed by N-nosylation, removal of the SEM-groups and cyclisation using a Mitsunobu reaction. Denosylation then gave the 2-furyloxazolidinonyl-fused piperidines, the (1RS,2SR,6SR)-epimer showing an allosteric agonistic effect on M1 receptors. Further studies resulted in the synthesis of other 2-substituted 4,7-diaza-9-oxabicyclo[4.3.0]nonan-8-ones and an analogous tetrahydropyran.

Increasing mean arterial pressure during cardiac surgery does not reduce the rate of postoperative acute kidney injury

Introduction:

We hypothesized that the optimization of renal haemodynamics by maintaining a high level of mean arterial blood pressure (MAP) during cardiopulmonary bypass (CPB) could reduce the rate of acute kidney injury (AKI) in high-risk patients.

Methods:

In this randomized, controlled study, we enrolled 300 patients scheduled for elective cardiac surgery under cardiopulmonary bypass. All had known risk factors of AKI: serum creatinine clearance between 30 and 60 ml/min for 1.73m2 or two factors among the following: age >60 years, diabetes mellitus, diffuse atherosclerosis. After a standardized fluid loading, the MAP was maintained between 75-85 mmHg during CPB with norepinephrine (High Pressure, n=147) versus 50-60 mmHg in the Control (n=145). AKI was defined by a 30% increased of serum creatinine (sCr). We further tested others definitions for AKI: RIFLE classification, 50% rise of sCr and the need for haemodialysis.

Results:

The pressure endpoints were achieved in both the High Pressure (79 ± 6 mmHg) and the Control groups (60 ± 6 mmHg; p<0.001). The rate of AKI did not differ by group (17% vs. 17%; p=1), whatever the criteria used for AKI. The length of stay in hospital (9.5 days [7.9-11.2] vs. 8.2 [7.1-9.4]) and the rate of death at day 28 (2.1% vs. 3.4%) and at six months (3.4% vs. 4.8%) did not differ between the groups.

Conclusion:

Maintaining a high level of MAP (on average) during normothermic CPB does not reduce the risk of postoperative AKI. It does not alter the length of hospital stay or the mortality rate.

Larvicidal activity of extracts from Artemisia species against Culex pipiens L. mosquito: comparing endemic versus ubiquist species for effectiveness

The larvicidal activity of ethanolic leaf extracts from two Artemisia species, Artemisia campestris var. glutinosa and A. molinieri, on mosquito Culex pipiens Linnaeus (Diptera, Culicidae) larvae was investigated. Since A. molinieri is a rare and protected species confined to temporary ponds of Southern France, its toxic activity may help to value this species and to finance its conservation. A. molinieri extracts showed a higher larvicidal activity (from 50 ppm (K=9.488, DDL=4, P<0.001)) than those from A. campestris var glutinosa (from 500 ppm (K=9.488, DDL=4, P<0.01)) after 48 h of exposure. Calculated lethal concentrations, after 48 h of exposure, (LC(50)) were low, 9091 and 9898 ppm for A. molinieri and A. campestris var. glutinosa extracts, respectively, but using a non-pollutant solvent (ethanol). However, A. molinieri may be valued as an environmentally friendly biocide and developing its culture may be of interest for both pesticide activity and conservation purpose.

Organic pollution and genotoxicity of sediments of the Palun marshes (Berre lagoon, France)

The impact of industrial, rural, and urban activities on two runnels (B1, B2, and B3 from Beausset runnel and V1 and V2 from Vallat du Ceinturon runnel) located in the Palun marshes (Berre lagoon, France) was evaluated by analyzing 16 polycyclic aromatic hydrocarbons (PAHs), 1-nitropyrene (1-NP), 1-aminopyrene (1-AP), and six pesticides in sediment samples. The mutagenicity was assessed with the Salmonella mutagenicity test using tester strains TA98+S9 Mix and YG1041 +/- S9 Mix. The clastogenicity was evaluated with the micronucleus assay on Chinese Ovarian cells +/- S9 Mix. A gradient of PAHs concentrations was observed from B1 (3359 microg kg(-1) dry weight [dw]), close to industrial zones, to V2 (497 microg kg(-1) dw), away from the source of pollution. Similar gradient was noted for 1-AP (from B1: 11.8 microg kg(-1) dw to V2: 0.6 microg kg(-1) dw). However, this trend was not observed in 1-NP concentrations (concentrations ranged from 1.2 microg kg(-1) dw [V1] to 0.4 microg kg(-1) dw [B1]). Pesticides were detected in all samples. Diazinon and dieldrin were found in high concentrations in B1 extracts (74.5 and 39.9 microg.kg(-1) dw, respectively). All the sediments except V2 were mutagenic with strain TA98+S9 Mix. The mutagenicity was linked to the presence of PAHs (V1), nitroarenes (B1 and B3) and aromatic amines (B2). All sediments were clastogenic with and without S9 Mix except V1 extract, which was negative without S9 Mix. Overall, the two runnels in the Palun marshes were found to be polluted by many organic compounds that originate from direct human activities and pose a significant genotoxic risk.

Molecular characterization of the invasive Asian tiger mosquito, Aedes (Stegomyia) albopictus (Diptera: Culicidae) in Corsica

The Asian tiger mosquito Aedes albopictus, vector of various human viruses and parasites, has recently spread and established in many temperate regions including European countries. In the present study, we developed a simple PCR-based assay (the amplification of the internal transcribed spacer ITS2 within nuclear ribosomal rDNA) for molecular identification of A. albopictus and confirmed its presence in Corsica island. This assay may (i) facilitate future large scale studies and avoid misidentifications, especially because of the presence of co-occurring close species in this island and (ii) contribute to the monitoring of A. albopictus populations required for targeted control programs.