From 5-HMF to Novel Cyclopentenone-Based Aza Spirocycles: An Intramolecular Aza-Piancatelli Reaction in Action.

With a double objective to upgrade biobased 5-HMF and to access to original spirocycles via an intramolecular aza-Piancatelli reaction, a multistep sequence was designed toward appropriate furylcarbinols. The impacts of both the nucleophiles, arylamines compared to alkoxyamines, and the length of the intramolecular tether were studied. After an in-depth evaluation of the different parameters, an extension of the scope provided a library of original azaspiro[4.5]non-8-en-7-ones and azaspiro[4.6]dec-3-en-2-ones whose skeletons have so far never been listed. The application of the aza-Piancatelli reaction associated with the use of biobased HMF in fine chemistry gives credit to the development of novative structures, as raised by the green chemistry community. Combining efforts in synthetic methodology with integration of biosourced platforms could open the way to new molecules exhibiting different properties from the ones raised from petrochemical sources.

Borrowing hydrogen C-alkylation with secondary saturated heterocyclic alcohols.

The borrowing hydrogen methodology (BH) has emerged as a powerful tool for the rapid construction of C-C bonds, offering a greener alternative to traditional multi-step syntheses. This methodology involves the activation of inactivated alcohols followed by condensation or aldolization, ultimately leading to the regeneration of the saturated product. Herein, we report the C-alkylation of a hindered ketone with challenging secondary saturated heterocyclic alcohols. Our study encompasses the optimization of reaction conditions using either an iridium or a ruthenium catalyst and exploration of substrate scope. We demonstrate the efficient synthesis of substituted pyrrolidines and piperidines directly from a triol precursor, showcasing the versatility of this methodology. Moreover, we illustrate the post-functionalization of BH products, significantly broadening their chemical utility.

What is a supercoiling-sensitive gene? Insights from topoisomerase I inhibition in the Gram-negative bacterium Dickeya dadantii.

DNA supercoiling is an essential mechanism of bacterial chromosome compaction, whose level is mainly regulated by topoisomerase I and DNA gyrase. Inhibiting either of these enzymes with antibiotics leads to global supercoiling modifications and subsequent changes in global gene expression. In previous studies, genes responding to DNA relaxation induced by DNA gyrase inhibition were categorised as 'supercoiling-sensitive'. Here, we studied the opposite variation of DNA supercoiling in the phytopathogen Dickeya dadantii using the non-marketed antibiotic seconeolitsine. We showed that the drug is active against topoisomerase I from this species, and analysed the first transcriptomic response of a Gram-negative bacterium to topoisomerase I inhibition. We find that the responding genes essentially differ from those observed after DNA relaxation, and further depend on the growth phase. We characterised these genes at the functional level, and also detected distinct patterns in terms of expression level, spatial and orientational organisation along the chromosome. Altogether, these results highlight that the supercoiling-sensitivity is a complex feature, which depends on the action of specific topoisomerases, on the physiological conditions, and on their genomic context. Based on previous in vitro expression data of several promoters, we propose a qualitative model of SC-dependent regulation that accounts for many of the contrasting transcriptomic features observed after DNA gyrase or topoisomerase I inhibition.

Ir-Catalyzed Synthesis of Functionalized Pyrrolidines and Piperidines Using the Borrowing Hydrogen Methodology.

The Ir(III)-catalyzed synthesis of 3-pyrrolidinols and 4-piperidinols combining 1,2,4-butanetriol or 1,3,5-pentanetriol with primary amines was carried out. This borrowing hydrogen methodology was further extended to the sequential diamination of triols leading to amino-pyrrolidines and amino-piperidines.

Design of a structure-activity relationship model of vitamin K epoxide reductase (VKORC1) inhibitors combining chemical synthesis of new compounds, enzymatic assays and molecular modelling.

Vitamin K antagonists (VKAs) anticoagulants have been used since the 1950s as medicines and rodenticides. These molecules are mainly 4-hydroxycoumarin derivatives and act by inhibiting the vitamin K epoxide reductase (VKORC1), an endoplasmic reticulum membrane resident enzyme. However, many VKORC1 mutations have been reported over the last decade, inducing VKAs resistances and thus treatments failures. Although studies have reported experimental and computational investigations of VKAs based on VKORC1 structural homology models, the development of new effective anticoagulants has been quite complex due to the lack of structural data and reliable structure-activity relationships. However, the recent publication of VKORC1 crystal structure provides new information for further studies. Based on these findings, we combined chemical synthesis, enzymatic assays and molecular modelling methods to design a structure-activity relationship (SAR) model. Our results proved that the lipophilicity, the membrane permeability of inhibitors and their affinity towards human VKORC1 enzyme are the main characteristics for potent anticoagulants. Our SAR model managed to rank compounds according to their ability to inhibit the human VKORC1. Such a tool might constitute an alternative to evaluate new molecules potency before their chemical synthesis and biological assessment and might assist the development of new VKAs.

Membrane plasticity induced by myo-inositol derived archaeal lipids: chemical synthesis and biophysical characterization.

Archaeal membrane lipids have specific structures that allow Archaea to withstand extreme conditions of temperature and pressure. In order to understand the molecular parameters that govern such resistance, the synthesis of 1,2-di-O-phytanyl-sn-glycero-3-phosphoinositol (DoPhPI), an archaeal lipid derived from myo-inositol, is reported. Benzyl protected myo-inositol was first prepared and then transformed to phosphodiester derivatives using a phosphoramidite based-coupling reaction with archaeol. Aqueous dispersions of DoPhPI alone or mixed with DoPhPC can be extruded and form small unilamellar vesicles, as detected by DLS. Neutron, SAXS, and solid-state NMR demonstrated that the water dispersions could form a lamellar phase at room temperature that then evolves into cubic and hexagonal phases with increasing temperature. Phytanyl chains were also found to impart remarkable and nearly constant dynamics to the bilayer over wide temperature ranges. All these new properties of archaeal lipids are proposed as providers of plasticity and thus means for the archaeal membrane to resist extreme conditions.

Natural-product-inspired design and synthesis of two series of compounds active against Trypanosoma cruzi: Insights into structure-activity relationship, toxicity, and mechanism of action.

Chemical scaffolds of natural products have historically been sources of inspiration for the development of novel molecules of biological relevance, including hit and lead compounds. To identify new compounds active against Trypanosoma cruzi, we designed and synthesized 46 synthetic derivatives based on the structure of two classes of natural products: tetrahydrofuran lignans (Series 1) and oxazole alkaloids (Series 2). Compounds were screened in vitro using a cellular model of T. cruzi infection. In the first series of compounds, 11 derivatives of hit compound 5 (EC50 = 1.1 µM) were found to be active; the most potent (7, 8, and 13) had EC50 values of 5.1-34.2 µM. In the second series, 17 analogs were found active at 50 µM; the most potent compounds (47, 49, 59, and 63) showed EC50 values of 24.2-49.1 µM. Active compounds were assessed for selectivity, hemocompatibility, synergistic potential, effects on mitochondrial membrane potential, and inhibitory effect on trypanothione reductase. All active compounds showed low toxicity against uninfected THP-1 cells and human erythrocytes. The potency of compounds 5 and 8 increased steadily in combination with benznidazole, indicating a synergistic effect. Furthermore, compounds 8, 47, 49, 59, and 63 inhibited parasitic mitochondria in a dose-dependent manner. Although increased reactive oxygen species levels might lead to mitochondrial effects, the results indicate that the mechanism of action of the compounds is not dependent on trypanothione reductase inhibition. In silico calculation of chemical descriptors and principal component analysis showed that the active compounds share common chemical features with other trypanocidal molecules and are predicted to have a good ADMET profile. Overall, the results suggest that the compounds are important candidates to be further studied for their potential against T. cruzi.

Straightforward Synthesis of Chiral Terpenoid Building Blocks by Ru-Catalyzed Enantioselective Hydrogenation.

Starting from commercially available (R)- and (S)-ß-citronellol, two strategies were designed to synthesize all four stereoisomers of 2,6-dimethyloctane monoterpene chirons in four or five steps in 32-47% overall yield. The desired fragments were obtained by a key Ru-catalyzed asymmetric olefin hydrogenation step under moderate temperature (50 °C), pressure (4 bar), and low catalyst loadings (0.5 mol %) under optimized conditions. Screening of commercially available catalysts highlighted the key role of DM-SEGPHOS as an economically advantageous alternative to commonly used H8-BINAP for equal performances. These results open new possibilities for versatile and scalable syntheses of these useful building blocks.

Diastereoselective Iridium-Catalyzed Amination of Biosourced Isohexides Through Borrowing Hydrogen Methodology.

A novel direct and diastereoselective amination of biosourced monobenzylated isohexides has been developed through borrowing hydrogen methodology using a cooperative catalysis between an iridium complex and a phosphoric acid. We also report herein the first regio- and diastereoselective direct amination of isosorbide.

The Piancatelli reaction and its variants: recent applications to high added-value chemicals and biomass valorization.

The Piancatelli reaction, also called the Piancatelli rearrangement, consists in the direct conversion of furfuryl alcohols to cyclopentenone derivatives through a furan ring opening-electrocyclization process. Discovered in the late 70's, this reaction has been scarcely used for more than 40 years but recently has been the focus of particular interest from the scientific community and an increasing number of publications on the topic have emerged in the last few years. The first part of this review provides an overview of the recent achievements in classical Piancatelli reactions, discussing reaction conditions and catalytic systems, whereas the second part focuses on the variants recently developed, including the use of new nucleophiles in the process. Finally, the third part of this review deals with the recent application of this transformation to the production of commodity chemicals from renewable carbon feedstocks based on sugar-derived furanic platforms.

Synthesis and biological evaluation of C-3 aliphatic coumarins as vitamin K antagonists.

Since the discovery of Warfarin in the 1940s, the design of new warfarin-derived anticoagulants for rodent management has been challenging, with mainly structural modifications performed on the C3 position of the coumarin skeleton. In order to better understand the pharmacomodulation of such derivatives, we have synthesized a family of C3 (linear and branched) alkyl-4-hydroxycoumarins, which led to the identification of compounds 5e and 5f as potential short-term active anticoagulants.

A continuous spectrophotometric assay that distinguishes between phospholipase A1 and A2 activities.

A new spectrophotometric assay was developed to measure, continuously and specifically, phospholipase A1 (PLA1) or phospholipase A2 (PLA2) activities using synthetic glycerophosphatidylcholines (PCs) containing α-eleostearic acid, either at the sn-1 position [1-α-eleostearoyl-2-octadecyl-rac-glycero-3-phosphocholine (EOPC)] or at the sn-2 position [1-octadecyl-2-α-eleostearoyl-rac-glycero-3-phosphocholine (OEPC)]. The substrates were coated onto the wells of microtiter plates. A nonhydrolyzable ether bond, with a non-UV-absorbing alkyl chain, was introduced at the other sn position to prevent acyl chain migration during lipolysis. Upon enzyme action, α-eleostearic acid is liberated and then solubilized into the micellar phase. The PLA1 or PLA2 activity was measured by the increase in absorbance at 272 nm due to the transition of α-eleostearic acid from the adsorbed to the soluble state. EOPC and OEPC differentiate, with excellent accuracy, between PLA1 and PLA2 activity. Lecitase(®), guinea pig pancreatic lipase-related protein 2 (known to be a PLA1 enzyme), bee venom PLA2, and porcine pancreatic PLA2 were all used to validate the assay. Compared with current assays used for continuously measuring PLA1 or PLA2 activities and/or their inhibitors, the development of this sensitive enzymatic method, using coated PC substrate analogs to natural lipids and based on the UV spectroscopic properties of α-eleostearic acid, is a significant improvement.

Development of an Ecofriendly Anticoagulant Rodenticide Based on the Stereochemistry of Difenacoum.

Difenacoum, an antivitamin K anticoagulant, has been widely used as rodenticide to manage populations of rodents. Difenacoum belongs to the second generation of anticoagulant, and, as all the molecules belonging to the second generation of anticoagulant, difenacoum is often involved in primary poisonings of domestic animals and secondary poisonings of wildlife by feeding contaminated rodents. To develop a new and ecofriendly difenacoum, we explored in this study the differences in properties between diastereomers of difenacoum. Indeed, the currently commercial difenacoum is a mixture of 57% of cis-isomers and 43% of trans-isomers. Cis- and trans-isomers were thus purified on a C18 column, and their respective pharmacokinetic properties and their efficiency to inhibit the coagulation of rodents were explored. Tissue persistence of trans-isomers was shown to be shorter than that of cis-isomers with a half-life fivefold shorter. Efficiency to inhibit the vitamin K epoxide reductase activity involved in the coagulation process was shown to be similar between cis- and trans-isomers. The use of trans-isomers of difenacoum allowed to drastically reduce difenacoum residues in liver and other tissues of rodents when the rodent is moribund. Therefore, secondary poisonings of wildlife should be decreased by the use of difenacoum largely enriched in trans-isomers.

Synthesis of benzofuran derivatives as selective inhibitors of tissue-nonspecific alkaline phosphatase: effects on cell toxicity and osteoblast-induced mineralization.

Tissue-nonspecific alkaline phosphatase (TNAP) by hydrolyzing pyrophosphate, an inhibitor of apatite formation, promotes extracellular matrix calcification during bone formation and growth, as well as during ectopic calcification under pathological conditions. TNAP is a target for the treatment of soft tissue pathological ossification. We synthesized a series of benzofuran derivatives. Among these, SMA14, displayed TNAP activity better than levamisole. SMA14 was found to be not toxic at doses of up to 40µM in osteoblast-like Saos-2 cells and primary osteoblasts. As probed by Alizarin Red staining, this compound inhibited mineral formation in murine primary osteoblast and in osteoblast-like Saos-2 cells.

Nitrogen-functionalized Isohexides in Asymmetric Induction.

Biosourced isohexides have attracted the considerable attention of both the academic and industrial chemistry communities over the last 50 years. This highlight focuses on the synthesis of nitrogen-containing isohexides and their applications in asymmetric catalysis.

Synthetic applications of hypophosphite derivatives in reduction.

The development of new tools for the reduction of organic functions to reach high chemo- and stereo-selectivity is an important research domain. Although, aluminum and boron hydrides are commonly used, they suffer from environmentally and safety issues. In particular, at industrial scale, the search for more specific and efficient reagents with a lower ecological impact remains one of the main objectives of organic chemists. This review captures highlights from literature concerning phosphonic and phosphinic acid derivatives as reducing agents and evaluates their potential as alternatives, in particular to boron and aluminum hydrides.

The Use of 5-Hydroxymethylfurfural (5-HMF) in Multi-Component Hantzsch Dihydropyridine Synthesis.

The renewable 5-hydroxymethylfurfural (5-HMF) has gained a wide interest from the chemistry community as a valuable biobased platform opening the way to many applications. Despite an impressive number of publications reporting either its preparation or its functionalization, its direct use in fine chemistry, and especially in multi-component reaction (MCR), is less reported. Here, we report a complete study of the use of 5-HMF in the Hantzsch dihydropyridines synthesis. The strategy was applied to a scope of ß-dicarbonyl molecules (including ß-ketoesters and 1,3-diketones) in a 3-component procedure leading to a series of symmetrical 1,4-dihydropyridines derived from 5-HMF in excellent yields. The study was extended to the 4-component protocol using one equivalent of a ß-ketoester and one equivalent of 5,5-dimethyl-1,3-cyclohexanedione (dimedone), which efficiently provided the corresponding unsymmetrical dihydropyridines.

Inhibitors of tissue-nonspecific alkaline phosphatase: design, synthesis, kinetics, biomineralization and cellular tests.

Chronic kidney disease (CKD) is associated with numerous metabolic and endocrine disturbances, including abnormalities of calcium and phosphate metabolism and an inflammatory syndrome. The latter occurs early in the course of CKD and contributes to the development and progression of vascular calcification. A few therapeutic strategies are today contemplated to target vascular calcification in patients with CKD: vitamin K2, calcimimetics and phosphate binders. However, none has provided complete prevention of vascular calcification and there is an urgent need for alternate efficient treatments. Recent findings indicate that tissue-nonspecific alkaline phosphatase (TNAP) may represent a very promising drug target due to its participation in mineralization by vascular smooth muscle cells. We report the synthesis of four levamisole derivatives having better inhibition property on TNAP than levamisole. Their IC50, Ki and water solubility have been determined. We found that the four inhibitors bind to TNAP in an uncompetitive manner and are selective to TNAP. Indeed, they do not inhibit intestinal and placental alkaline phosphatases. Survival MTT tests on human MG-63 and Saos-2 osteoblast-like cells have been performed in the presence of inhibitors. All the inhibitors are not toxic at concentrations that block TNAP activity. Moreover, they are able to significantly reduce mineralization in MG63 and Saos-2 osteoblast-like cells, indicating that they are promising molecules to prevent vascular calcification.

Splice variants of protein disulfide isomerase - identification, distribution and functional characterization in the rat.

BACKGROUND: Protein Disulfide Isomerase (PDI) enzyme is an emerging therapeutic target in oncology and hematology. Although PDI reductase activity has been studied with isolated fragments of the protein, natural structural variations affecting reductase activity have not been addressed. METHODS: In this study, we discovered four coding splice variants of the Pdi pre-mRNA in rats. In vitro Michaelis constants and apparent maximum steady-state rate constants after purification and distribution in different rat tissues were determined. RESULTS: The consensus sequence was found to be the most expressed splice variant while the second most expressed variant represents 15 to 35% of total Pdi mRNA. The third variant shows a quasi-null expression profile and the fourth was not quantifiable. The consensus sequence splice variant and the second splice variant are widely expressed (transcription level) in the liver and even more present in males. Measurements of the reductase activity of recombinant PDI indicate that the consensus sequence and third splice variant are fully active variants. The second most expressed variant, differing by a lack of signal peptide, was found active but less than the consensus sequence. GENERAL SIGNIFICANCE: Our work emphasizes the importance of taking splice variants into account when studying PDI-like proteins to understand the full biological functionalities of PDI.

Solvent-free Michael addition to non-protected 3-(2-nitrovinyl)indole by ultrasound activation.

A variety of nucleophiles provided by activated methylenes have been added on 3-(2-nitrovinyl)-1H-indole in very good to excellent yields, under sonication and solvent-free conditions, using solid potassium carbonate or sodium acetate as a base. Direct synthesis avoiding preliminary NH protection is reported and exemplified to 15 molecules.