Synthesis of Seven- and Eight-Membered Rings by a Brønsted Acid Catalyzed Cationic Carbocyclization of Biphenyl Embedded Enynes.

A Brønsted acid catalyzed cyclization of o-alkenyl-o'-alkynylbiaryls for the synthesis of biologically relevant dibenzo-fused medium-sized rings has been developed. The outcome of the cyclization is determined by the nature of the substituent at the alkyne, with arenes favoring seven-membered rings and alkyl substituents producing eight-membered rings. These reactions proceed via a vinyl cation, which is captured by water and, notably, by C-nucleophiles, such as electron-rich (hetero)arenes.

1,2,3-Benzotriazine Synthesis by Heterocyclization of p-Tosylmethyl Isocyanide Derivatives.

An efficient methodology to form 4-alkoxy- and 4-aryloxybenzo[d][1,2,3]triazines via an intramolecular heterocyclization of 1-azido-2-[isocyano(p-tosyl)methyl]benzenes under basic conditions has been developed. DFT calculations have been performed to further understand the mechanism of this heterocyclization, which occurs in good to excellent yields with a broad scope.

One-Pot (3 + 2) Cycloaddition-Isomerization-Oxidation of 2,2,2-Trifluorodiazoethane and Styryl Derivatives.

A facile access to 5-aryl-3-trifluoromethylpyrazoles has been developed by a one-pot (3 + 2) cycloaddition-isomerization-oxidation sequence employing 2,2,2-trifluorodiazoethane and styryl derivatives. A broad variety of functional groups and good yields are achieved under mild conditions. Additionally, the functionalization of 3-trifluoromethylpyrazoles was studied. DFT calculations of the cycloaddition transition state energies are consistent with the experimentally observed reactivity.

Gold-catalyzed endo-selective cyclization of alkynylcyclobutanecarboxamides: synthesis of cyclobutane-fused dihydropyridones.

Cyclobutane-fused dihydropyridones can be efficiently synthesized by a completely endo-selective gold-catalyzed cyclization of alkynylcyclobutanes bearing an appended amide, which proceeds under mild conditions. The observed selectivity, which is reversed from that previously observed for the cyclization of related alcohols and acids, is supported by DFT calculations.

Steviol glycosides as an alternative osmotic agent for peritoneal dialysis fluid.

Background: Peritoneal dialysis (PD) is a renal replacement technique that requires repeated exposure of the peritoneum to hyperosmolar PD fluids (PDFs). Unfortunately, it promotes alterations of the peritoneal membrane (PM) that affects its functionality, including mesothelial-mesenchymal transition (MMT) of mesothelial cells (MCs), inflammation, angiogenesis, and fibrosis. Glucose is the most used osmotic agent, but it is known to be at least partially responsible, together with its degradation products (GDP), for those changes. Therefore, there is a need for more biocompatible osmotic agents to better maintain the PM. Herein we evaluated the biocompatibility of Steviol glycosides (SG)-based fluids. Methods: The ultrafiltration and transport capacities of SG-containing and glucose-based fluids were analyzed using artificial membranes and an in vivo mouse model, respectively. To investigate the biocompatibility of the fluids, Met-5A and human omental peritoneal MCs (HOMCs) were exposed in vitro to different types of glucose-based PDFs (conventional 4.25% glucose solution with high-GDP level and biocompatible 2.3% glucose solution with low-GDP level), SG-based fluids or treated with TGF-ß1. Mice submitted to surgery of intraperitoneal catheter insertion were treated for 40 days with SG- or glucose-based fluids. Peritoneal tissues were collected to determine thickness, MMT, angiogenesis, as well as peritoneal washings to analyze inflammation. Results: Dialysis membrane experiments demonstrated that SG-based fluids at 1.5%, 1%, and 0.75% had a similar trend in weight gain, based on curve slope, as glucose-based fluids. Analyzing transport capacity in vivo, 1% and 0.75% SG-based fluid-exposed nephrectomized mice extracted a similar amount of urea as the glucose 2.3% group. In vitro, PDF with high-glucose (4.25%) and high-GDP content induced mesenchymal markers and angiogenic factors (Snail1, Fibronectin, VEGF-A, FGF-2) and downregulates the epithelial marker E-Cadherin. In contrast, exposition to low-glucose-based fluids with low-GDP content or SG-based fluids showed higher viability and had less MMT. In vivo, SG-based fluids preserved MC monolayer, induced less PM thickness, angiogenesis, leukocyte infiltration, inflammatory cytokines release, and MMT compared with glucose-based fluids. Conclusion: SG showed better biocompatibility as an osmotic agent than glucose in vitro and in vivo, therefore, it could alternatively substitute glucose in PDF.

Synthesis of BN-Polyarenes by a Mild Borylative Cyclization Cascade.

Reaction of BCl3 with suitably substituted o-alkynylanilines promotes a cascade reaction in which BN-polycyclic compounds are obtained via the formation of two new cycles and three new bonds in a single operational step. The reaction is highly efficient and takes place at room temperature, providing a very mild and straightforward strategy for the preparation of BN-aromatic compounds, which can be further transformed into a variety of BN-PAHs with different polycyclic cores and substituents.

Insight into the mechanism of molecular recognition between human Integrin-Linked Kinase and Cpd22 and its implication at atomic level.

ABSRACT: Pseudokinases have received increasing attention over the past decade because of their role in different physiological phenomena. Although pseudokinases lack several active-site residues, thereby hindering their catalytic activity, recent discoveries have shown that these proteins can play a role in intracellular signaling thanks to their non-catalytic functions. Integrin-linked kinase (ILK) was discovered more than two decades ago and was subsequently validated as a promising target for neoplastic diseases. Since then, only a few small-molecule inhibitors have been described, with the V-shaped pyrazole Cpd22 being the most interesting and characterized. However, little is known about its detailed mechanism of action at atomic level. In this study, using a combination of computational chemistry methods including PELE calculations, docking, molecular dynamics and experimental surface plasmon resonance, we were able to prove the direct binding of this molecule to ILK, thus providing the basis of its molecular recognition by the protein and the effect over its architecture. Our breakthroughs show that Cpd22 binding stabilizes the ILK domain by binding to the pseudo-active site in a similar way to the ATP, possibly modulating its scaffolding properties as pseudokinase. Moreover, our results explain the experimental observations obtained during Cpd22 development, thus paving the way to the development of new chemical probes and potential drugs.

Metal-Free Temperature-Controlled Regiodivergent Borylative Cyclizations of Enynes: BCl3 -Promoted Skeletal Rearrangement.

Metal-free borylative cyclization of biphenyl-embedded 1,3,5-trien-7-ynes in the presence of simple and inexpensive BCl3 provided synthetically useful borylated building blocks. The outcome of the process depends on the reaction temperature, with borylated phenanthrenes obtained at 60 °C and phenanthrene-fused borylated cyclobutanes formed at 0 °C. Based on DFT calculations, a mechanism for these novel transformations has been proposed, which involves an uncommon skeletal rearrangement, including migration of a methyl group and alkyne fragmentation, unprecedented in BCl3 -promoted cyclization reactions.

Pyridazino-pyrrolo-quinoxalinium salts as highly potent and selective leishmanicidal agents targeting trypanothione reductase.

Fifteen pyridazino-pyrrolo-quinoxalinium salts were synthesized and tested for their antiprotozoal activity against Leishmania infantum amastigotes. Eleven of them turned out to be leishmanicidal, with EC50 values in the nanomolar range, and displayed low toxicity against the human THP-1 cell line. Selectivity indices for these compounds range from 10 to more than 1000. Compounds 3b and 3f behave as potent inhibitors of the oxidoreductase activity of the essential enzyme trypanothione disulfide reductase (TryR). Interestingly, binding of 3f is not affected by high trypanothione concentrations, as revealed by the noncompetitive pattern of inhibition observed when tested in the presence of increasing concentrations of this substrate. Furthermore, when analyzed at varying NADPH concentrations, the characteristic pattern of hyperbolic uncompetitive inhibition supports the view that binding of NADPH to TryR is a prerequisite for inhibitor-protein association. Similar to other TryR uncompetitive inhibitors for NADPH, 3f is responsible for TryR-dependent reduction of cytochrome c in a reaction that is typically inhibited by superoxide dismutase.

Tripeptides as Integrin-Linked Kinase Modulating Agents Based on a Protein-Protein Interaction with α-Parvin.

Integrin-linked kinase (ILK) has emerged as a controversial pseudokinase protein that plays a crucial role in the signaling process initiated by integrin-mediated signaling. However, ILK also exhibits a scaffolding protein function inside cells, controlling cytoskeletal dynamics, and has been related to non-neoplastic diseases such as chronic kidney disease (CKD). Although this protein always acts as a heterotrimeric complex bound to PINCH and parvin adaptor proteins, the role of parvin proteins is currently not well understood. Using in silico approaches for the design, we have generated and prepared a set of new tripeptides mimicking an α-parvin segment. These derivatives exhibit activity in phenotypic assays in an ILK-dependent manner without altering kinase activity, thus allowing the generation of new chemical probes and drug candidates with interesting ILK-modulating activities.

1,10a-Dihydro-1-aza-10a-boraphenanthrene and 6a,7-Dihydro-7-aza-6a-boratetraphene: Two New Fluorescent BN-PAHs.

Previously unknown 1,10a-dihydro-1-aza-10a-boraphenanthrene and 6a,7-dihydro-7-aza-6a-boratetraphene have been efficiently synthesized. Bromination of these BN-PAHs proceeds with complete regioselectivity, resulting in the formation of different substituted derivatives via cross-coupling reactions. These compounds exhibit rather high fluorescence quantum yields (up to ϕF = 0.80).

Pyrrolo[1,2-a]quinoxal-5-inium salts and 4,5-dihydropyrrolo[1,2-a]quinoxalines: Synthesis, activity and computational docking for protein tyrosine phosphatase 1B.

Protein tyrosine phosphatase (PTP1B) is an interesting therapeutical target for diabetes, obesity, heart disease and cancer. As such, inhibition of PTP1B using orally administered drugs is still being pursued by academia and pharmaceutical companies. The failure of catalytic-site inhibitors led to the focus in this field being switched to allosteric inhibitors. To date, the non-competitive inhibitors that have reached clinical trials target the site formed by the α3/α6/α7 tunnel or the site found in a disordered C-terminal non-catalytic segment. Herein, pyrrolo[1,2-a]quinoxal-5-inium salts and 4,5-dihydropyrrolo[1,2-a]quinoxalines are synthesized from pyrrolo[1,2-a]quinoxalines by alkylation and reduction, respectively. These compounds showed no toxicity in HepG2 cells and exhibited inhibitory activity against PTP1B, with inhibition percentages of between 37% and 53% at 1 µM and activities (IC50) of between 0.25 and 1.90 µM. The inhibitory activity against T-cell protein tyrosine phosphatase (TC-TPT) was also assayed, with 4,5-dihydropyrrolo[1,2-a]quinoxalines being found to be slightly more active and selective. Compounds from the two series behave as insulin mimetics since they exhibit enhancement of glucose uptake in C2C12 cells. Computational docking studies provide information about the putative binding mode for both series and the preference for the α3/α6/α7 allosteric tunnel.

Enantioselective Copper-Catalyzed Synthesis of Trifluoromethyl-Cyclopropylboronates.

A copper-catalyzed enantioselective cyclopropanation involving trifluorodiazoethane in the presence of alkenyl boronates has been developed. This transformation enables the preparation of 2-substituted-3-(trifluoromethyl)cyclopropylboronates with high levels of stereocontrol. The products are valuable synthetic intermediates by transformation of the boronate group. This methodology can be applied to the synthesis of novel trifluoromethylated analogues of trans-2-arylcyclopropylamines, which are prevalent motifs in biologically active compounds.

A Computer-Driven Scaffold-Hopping Approach Generating New PTP1B Inhibitors from the Pyrrolo[1,2-a]quinoxaline Core.

Protein tyrosine phosphatase 1B (PTP1B) is a very promising target for the treatment of metabolic disorders such as type II diabetes mellitus. Although it was validated as a promising target for this disease more than 30 years ago, as yet there is no drug in advanced clinical trials, and its biochemical mechanism and functions are still being studied. In the present study, based on our experience generating PTP1B inhibitors, we have developed and implemented a scaffold-hopping approach to vary the pyrrole ring of the pyrrolo[1,2-a]quinoxaline core, supported by extensive computational techniques aimed to explain the molecular interaction with PTP1B. Using a combination of docking, molecular dynamics and end-point free-energy calculations, we have rationally designed a hypothesis for new PTP1B inhibitors, supporting their recognition mechanism at a molecular level. After the design phase, we were able to easily synthesize proposed candidates and their evaluation against PTP1B was found to be in good concordance with our predictions. Moreover, the best candidates exhibited glucose uptake increments in cellulo model, thus confirming their utility for PTP1B inhibition and validating this approach for inhibitors design and molecules thus obtained.

Two-photon activated precision molecular photosensitizer targeting mitochondria.

Mitochondria metabolism is an emergent target for the development of novel anticancer agents. It is amply recognized that strategies that allow for modulation of mitochondrial function in specific cell populations need to be developed for the therapeutic potential of mitochondria-targeting agents to become a reality in the clinic. In this work, we report dipolar and quadrupolar quinolizinium and benzimidazolium cations that show mitochondria targeting ability and localized light-induced mitochondria damage in live animal cells. Some of the dyes induce a very efficient disruption of mitochondrial potential and subsequent cell death under two-photon excitation in the Near-infrared (NIR) opening up possible applications of azonia/azolium aromatic heterocycles as precision photosensitizers. The dipolar compounds could be excited in the NIR due to a high two-photon brightness while exhibiting emission in the red part of the visible spectra (600-700 nm). Interaction with the mitochondria leads to an unexpected blue-shift of the emission of the far-red emitting compounds, which we assign to emission from the locally excited state. Interaction and possibly aggregation at the mitochondria prevents access to the intramolecular charge transfer state responsible for far-red emission.

Pyrrolo[1,2-a]quinoxalines: Insulin Mimetics that Exhibit Potent and Selective Inhibition against Protein Tyrosine Phosphatase 1B.

PTP1B dephosphorylates insulin receptor and substrates to modulate glucose metabolism. This enzyme is a validated therapeutic target for type 2 diabetes, but no current drug candidates have completed clinical trials. Pyrrolo[1,2-a]quinoxalines substituted at positions C1-C4 and/or C7-C8 were found to be nontoxic to cells and good inhibitors in the low- to sub-micromolar range, with the 4-benzyl derivative being the most potent inhibitor (0.24 µm). Some analogues bearing chlorine atoms at C7 and/or C8 kept potency and showed good selectivity compared to TCPTP (selectivity index >40). The most potent inhibitors behaved as insulin mimetics by increasing glucose uptake. The 4-benzyl derivative inhibited insulin receptor substrate 1 and AKT phosphorylation. Molecular docking and molecular dynamics simulations supported a putative binding mode for these compounds to the allosteric α3/α6/α7 pocket, but inconsistent results in enzyme inhibition kinetics were obtained due to the high tendency of these inhibitors to form stable aggregates. Computational calculations supported the druggability of inhibitors.

Selective Synthesis of Phenanthrenes and Dihydrophenanthrenes via Gold-Catalyzed Cycloisomerization of Biphenyl Embedded Trienynes.

Readily available o'-alkenyl-o-alkynylbiaryls, a particular type of 1,7-enynes, undergo a selective cycloisomerization reaction in the presence of a gold(I) catalyst to give interesting phenanthrene and dihydrophenanthrene derivatives in high yields. The solvent used provokes a switch in the evolution of the gold intermediate and plays a key role in the reaction outcome.

The pHLIP system as a vehicle for microRNAs in the kidney. / El sistema pHLIP como vehículo de microRNA en el riñón.

MicroRNAs (miRNAs) are small endogenous RNAs that regulate gene expression through post-transcriptional repression of their target messenger RNAs. A study of changes in expression of certain miRNAs in the kidney has supplied evidence on their pathogenic role and therapeutic potential in nephrology. This review proposes a nanotechnology approach based on the binding of analogs or inhibitors of miRNAs formed by peptide nucleic acids (PNAs) to peptides with a transmembrane structure sensitive to a low pH, called pHLIPs (pH [low] insertion peptides). The review draws on the concept that an acidic pH in the microenvironment of the renal tubule may facilitate concentration and distribution of the pHLIP-PNA complex in this organ. In this context, we have demonstrated for the first time that targeted administration of miR-33 inhibitors with the pHLIP system effectively prevents the development of renal fibrosis, thus opening up this technology to new strategies for diagnosis and treatment of kidney diseases.

Expanding the BN-embedded PAH family: 4a-aza-12a-borachrysene.

Previously unknown 4a-aza-12a-borachrysene has been synthesized in only four steps. The reactions of this BN-embedded PAH with bromine and organolithium compounds proceed with complete regioselectivity, resulting in the formation of nine derivatives. One of these, a phenylalkynyl-substituted derivative, exhibits a remarkably high fluorescence quantum yield (ΦF = 0.68).

Synthesis and Photophysical Behavior of a Highly Fluorescent Family of Unsymmetrical Organoboron Complexes Containing 5-(Pyridin-2-ylmethylene)imidazolidine-2,4-dione Moieties.

A new and highly fluorescent family of unsymmetrical organoboron complexes containing 5-(pyridin-2-ylmethylene)imidazolidine-2,4-dione moieties has been synthesized in three steps. These compounds show strong absorptions covering a wide range of the UV-vis spectrum and are strongly emissive (ϕf of up to 0.92 in CH3CN). Moreover, two fluorophores that include an alkyne or an azide group at the end of the alkyl chain and with potential utility in bioorthogonal chemistry have been developed. One of these, in which the glycol substituent provides an enhanced water solubility without compromising the fluorescence (ϕf = 0.85 in water), may be of particular importance.