A Transient Directing Group Strategy Enables Enantioselective Multicomponent Organofluorine Synthesis.

The vicinal fluorofunctionalization of alkenes represents an expedient strategy for converting feedstock olefins into valuable fluorinated molecules and as such has garnered significant attention from the synthetic community; however, current methods remain limited in terms of scope and selectivity. Here we report the site-selective palladium-catalyzed three-component coupling of alkenylbenzaldehydes, arylboronic acids, and N-fluoro-2,4,6-trimethylpyridinium hexafluorophosphate facilitated by a transient directing group. The synthetically enabling methodology constructs vicinal stereocenters with excellent regio-, diastereo-, and enantioselectivities, forging products that map onto bioactive compounds.

Organofluorine Hydrazone Derivatives as Multifunctional Anti-Alzheimer's Agents with CK2 Inhibitory and Antioxidant Features.

A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4-N(CH3 )2 residue or perfluorinated phenyl rings showed high activity in the radical-scavenging assays and possess nanomolar IC50 values in the kinase assays.

Anticancer active trifluoromethylated fused triazinones are safe for early-life stages of zebrafish (Danio rerio) and reveal a proapoptotic action.

The main purpose of this investigation was to evaluate the effect of anticancer active compounds (I-VIII) on zebrafish development in order to select the safest molecules. Larval mortality, embryo hatchability and malformations were end-points used to assess the acute toxicity among embryos and larvae from compounds-/pemetrexed-treated and control groups. LC50 and MNLC (maximal non-lethal concentration) were determined. Lipophilicity-dependent structure-toxicity relationships were established. The results clearly indicated that the majority of test molecules are safe for zebrafish individuals and simultaneously are less toxic than an anticancer agent - pemetrexed. The subsequent aim of this study was to elucidate the molecular mechanism of antiproliferative activity of the most selective compounds. Substantially increased activation of caspase-6 and -8 in cancerous cell lines confirmed the proapoptotic action of molecules examined. Considering the safety for zebrafish individuals, the title compounds as inducers of apoptosis are promising drug candidates in the preclinical phase of drug development.

Metallaphotoredox Perfluoroalkylation of Organobromides.

Ruppert-Prakash type reagents (TMSCF3, TMSC2F5, and TMSC3F7) are readily available, air-stable, and easy-to-handle fluoroalkyl sources. Herein, we describe a mild, copper-catalyzed cross-coupling of these fluoroalkyl nucleophiles with aryl and alkyl bromides to produce a diverse array of trifluoromethyl, pentafluoroethyl, and heptafluoropropyl adducts. This light-mediated transformation proceeds via a silyl-radical-mediated halogen atom abstraction pathway, which enables perfluoroalkylation of a broad range of organobromides of variable steric and electronic demand. The utility of the method is demonstrated through the late-stage functionalization of several drug analogues.

Mononuclear Perfluoroalkyl-Heterocyclic Complexes of Pd(II): Synthesis, Structural Characterization and Antimicrobial Activity.

Two mononuclear Pd(II) complexes [PdCl2(pfptp)] (1) and [PdCl2(pfhtp)] (2), with ligands 2-(3-perfluoropropyl-1-methyl-1,2,4-triazole-5yl)-pyridine (pfptp) and 2-(3-perfluoroheptyl-1-methyl-1,2,4-triazole-5yl)-pyridine (pfhtp), were synthesized and structurally characterized. The two complexes showed a bidentate coordination of the ligand occurring through N atom of pyridine ring and N4 atom of 1,2,4-triazole. Both complexes showed antimicrobial activity when tested against both Gram-negative and Gram-positive bacterial strains.

Enantiodivergent α-Amino C-H Fluoroalkylation Catalyzed by Engineered Cytochrome P450s.

The introduction of fluoroalkyl groups into organic compounds can significantly alter pharmacological characteristics. One enabling but underexplored approach for the installation of fluoroalkyl groups is selective C( sp3)-H functionalization due to the ubiquity of C-H bonds in organic molecules. We have engineered heme enzymes that can insert fluoroalkyl carbene intermediates into α-amino C( sp3)-H bonds and enable enantiodivergent synthesis of fluoroalkyl-containing molecules. Using directed evolution, we engineered cytochrome P450 enzymes to catalyze this abiological reaction under mild conditions with total turnovers (TTN) up to 4070 and enantiomeric excess (ee) up to 99%. The iron-heme catalyst is fully genetically encoded and configurable by directed evolution so that just a few mutations to the enzyme completely inverted product enantioselectivity. These catalysts provide a powerful method for synthesis of chiral organofluorine molecules that is currently not possible with small-molecule catalysts.

Development of Theranostic Perfluorocarbon Nanoemulsions as a Model Non-Opioid Pain Nanomedicine Using a Quality by Design (QbD) Approach.

Pain nanomedicine is an emerging field in response to current needs of addressing the opioid crisis in the USA and around the world. Our group has focused on the development of macrophage-targeted perfluorocarbon nanoemulsions as inflammatory pain nanomedicines over the past several years. We present here, for the first time, a quality by design approach used to design pain nanomedicine. Specifically, we used failure mode, effects, and criticality analysis (FMECA) which identified the process and composition parameters that were most likely to impact nanoemulsion critical quality attributes (CQAs). From here, we applied a unique combination approach that compared multiple linear regression, boosted decision tree regression, and partial least squares regression methods in combination with correlation plots. The presented combination approach allowed for in-depth analyses of which formulation steps in the nanoemulsification processes control nanoemulsion droplet diameter, stability, and drug loading. We identified that increase in solubilizer (transcutol) content increased drug loading and decreased nanoemulsion stability. This was mitigated by inclusion of perfluorocarbon oil in the internal phase. We observed negative correlation (R2 = 0.4357, p value 0.0054) between the amount of PCE and the percent diameter increase (destabilization), and no correlation between processing parameters and percent diameter increase over time. Further, we identified that increased sonication time decreases nanoemulsion drug loading but does not significantly impact droplet diameter or stability. We believe the methods presented here can be useful in the development of various nanomedicines to produce higher-quality products with enhanced manufacturing and design control.

Synthesis and Biological Evaluation of Polyfluoroalkylated Antipyrines and their Isomeric O-Methylpyrazoles.

BACKGROUND: Formally belonging to the non-steroidal anti-inflammatory drug class pyrazolones have long been used in medical practices. OBJECTIVE: Our goal is to synthesize N-methylated 1-aryl-3-polyfluoroalkylpyrazolones as fluorinated analogs of antipyrine, their isomeric O-methylated derivatives resembling celecoxib structure and evaluate biological activities of obtained compounds. METHODS: In vitro (permeability) and in vivo (anti-inflammatory and analgesic activities, acute toxicity, hyperalgesia, antipyretic activity, "open field" test) experiments. To suggest the mechanism of biological activity, molecular docking of the synthesized compounds was carried out into the tyrosine site of COX-1/2. RESULTS: We developed the convenient methods for regioselective methylation of 1-aryl-3- polyfluoroalkylpyrazol-5-ols leading to the synthesis N-methylpyrazolones and O-methylpyrazoles as antipyrine and celecoxib analogs respectively. For the first time, the biological properties of new derivatives were investigated in vitro and in vivo. CONCLUSION: The trifluoromethyl antipyrine represents a valuable starting point in design of the lead series for discovery new antipyretic analgesics with anti-inflammatory properties.

Spontaneous Nucleation of Stable Perfluorocarbon Emulsions for Ultrasound Contrast Agents.

Phase-change contrast agents are rapidly developing as an alternative to microbubbles for ultrasound imaging and therapy. These agents are synthesized and delivered as liquid droplets and vaporized locally to produce image contrast. They can be used like conventional microbubbles but with the added benefit of reduced size and improved stability. Droplet-based agents can be synthesized with diameters on the order of 100 nm, making them an ideal candidate for extravascular imaging or therapy. However, their synthesis requires low boiling point perfluorocarbons (PFCs) to achieve activation (i.e., vaporization) thresholds within FDA approved limits. Minimizing spontaneous vaporization while producing liquid droplets using conventional methods with low boiling point PFCs can be challenging. In this study, a new method to produce PFC nanodroplets using spontaneous nucleation is demonstrated using PFCs with boiling points ranging from -37 to 56 °C. Sometimes referred to as the ouzo method, the process relies on saturating a cosolvent with the PFC before adding a poor solvent to reduce solvent quality, forcing droplets to spontaneously nucleate. This approach can produce droplets ranging from under 100 nm to over 1 µm in diameter. Ternary plots showing solvent and PFC concentrations leading to droplet nucleation are presented. Additionally, acoustic activation thresholds and size distributions with varying PFC and solvent conditions are measured and discussed. Finally, ultrasound contrast imaging is demonstrated using ouzo droplets in an animal model.

Formation of Non-Natural α,α-Disubstituted Amino Esters via Catalytic Michael Addition.

The enolate monoanion of amino esters is explored, and the first catalytic Michael addition of α-amino esters is demonstrated. These studies indicate that the acidity of the αC-H is the primary factor determining reactivity. Thus, polyfluorophenylglycine amino esters yield novel α-amino esters in the presence of a catalytic amount of a guanidine-derived base and Michael acceptors. Reactivity requires an acidic N-H, which is accomplished using common protecting groups such as N-Bz, N-Boc, and N-Cbz. Calculations and labeling experiments provide insight into the governing principles in which a key C-to-N proton transfer occurs, resulting in an expansion of the scope to include a number of natural amino esters. The study culminates with a late-stage functionalization of peptidic γ-secretase inhibitor, DAPT.

A General Approach to Biocompatible Branched Fluorous Tags for Increased Solubility in Perfluorocarbon Solvents.

A modular, cost-effective route to a library of branched fluorous tags with two short, biocompatible, fluorinated chains (C6F13) is reported. These branched fluorous tags provide high fluorous content without the use of long-chain linear perfluorocarbons, which have rising health concerns due to their bioaccumulation. By attaching these tags to a porphyrin, it is demonstrated that high solubility can be achieved in fluorous solvents that are readily cleared from mammals. This work enhances the biocompatibility of perfluorocarbon nanoemulsions for photodynamic therapy.

Synthesis, Structural Characterization, and Antiangiogenic Activity of Polyfluorinated Benzamides.

The introduction of fluorine into bioactive molecules is a matter of importance in medicinal chemistry. In this study, representatives of various chemical entities of fluoroaromatic compounds were synthesized. Depending on the reaction conditions, either tetrafluorophthalimides or ammonium tetrafluorophthalamates are accessible from tetrafluorophthalic anhydride and primary amines. Tetrafluorophthalamic acids undergo thermal decarboxylation to yield tetrafluorobenzamides. These could be successfully converted upon treatment with primary amines, in the course of an aromatic nucleophilic substitution, to 2,3,5-trifluorobenzamides with respective amino substituents at the 4-position. The five structure types were characterized by means of spectroscopic and crystallographic methods. The synthesized compounds were evaluated as inhibitors of angiogenesis by measuring microvessel outgrowth in a rat aortic ring assay. The biological activity was maintained throughout these different polyfluorinated chemotypes.

Fluorinated DNA Micelles: Synthesis and Properties.

Creating new functional building blocks that expand the versatility of nanostructures depends on bottom-up self-assembly of amphiphilic biomolecules. Inspired by the unique physicochemical properties of hydrophobic perfluorocarbons, coupled with the powerful functions of nucleic acids, we herein report the synthesis of a series of diperfluorodecyl-DNA conjugates (PF-DNA) which can efficiently self-assemble into micelles in aqueous solution. On the basis of the micelle structure, both target binding affinity and enzymatic resistance of the DNA probe can be enhanced. In addition, based on the hydrophobic effect, the PF-DNA micelles (PFDM) can actively anchor onto the cell membrane, offering a promising tool for cell-surface engineering. Finally, the PFDM can enter cells, which is significant for designing carriers for intracellular delivery. The combined advantages of the DNA micelle structure and the unique physicochemical properties of perfluorocarbons make these PFDM promising for applications in bioimaging and biomedicine.

Cardiac performance is limited by oxygen delivery to the mitochondria in the crystalloid-perfused working heart.

The left ventricular working, crystalloid-perfused heart is used extensively to evaluate basic cardiac function, pathophysiology, and pharmacology. Crystalloid-perfused hearts may be limited by oxygen delivery, as adding oxygen carriers increases myoglobin oxygenation and improves myocardial function. However, whether decreased myoglobin oxygen saturation impacts oxidative phosphorylation (OxPhos) is unresolved, since myoglobin has a much lower affinity for oxygen than cytochrome c oxidase (COX). In the present study, a laboratory-based synthesis of an affordable perfluorocarbon (PFC) emulsion was developed to increase perfusate oxygen carrying capacity without impeding optical absorbance assessments. In left ventricular working hearts, along with conventional measurements of cardiac function and metabolic rate, myoglobin oxygenation and cytochrome redox state were monitored using a novel transmural illumination approach. Hearts were perfused with Krebs-Henseleit (KH) or KH supplemented with PFC, increasing perfusate oxygen carrying capacity by 3.6-fold. In KH-perfused hearts, myoglobin was deoxygenated, consistent with cytoplasmic hypoxia, and the mitochondrial cytochromes, including COX, exhibited a high reduction state, consistent with OxPhos hypoxia. PFC perfusate increased aortic output from 76 ± 6 to 142 ± 4 ml/min and increased oxygen consumption while also increasing myoglobin oxygenation and oxidizing the mitochondrial cytochromes. These results are consistent with limited delivery of oxygen to OxPhos resulting in an adapted lower cardiac performance with KH. Consistent with this, PFCs increased myocardial oxygenation, and cardiac work was higher over a wider range of perfusate Po2. In summary, heart mitochondria are limited by oxygen delivery with KH; supplementation of KH with PFC reverses mitochondrial hypoxia and improves cardiac performance, creating a more physiological tissue oxygen delivery. NEW & NOTEWORTHY Optical absorbance spectroscopy of intrinsic chromophores reveals that the commonly used crystalloid-perfused working heart is oxygen limited for oxidative phosphorylation and associated cardiac work. Oxygen-carrying perfluorocarbons increase myocardial oxygen delivery and improve cardiac function, providing a more physiological mitochondrial redox state and emphasizing cardiac work is modulated by myocardial oxygen delivery.

Folate receptor-targeted ultrasonic PFOB nanoparticles: Synthesis, characterization and application in tumor-targeted imaging.

In this study, we aimed to determine an effective strategy for the synthesis of folate receptor (FR) targeted-nanoparticles (FRNPs). The nanoparticles used as ultrasound contrast agents (UCAs) were composed of a liquid core of perfluorooctyl bromide (PFOB) liposome and a targeted shell chemically conjugated with folic acid (FA) and polyethylene glycol (PEG). This was done in order to avoid recognition and clearance by the mononuclear phagocyte system [also known as the reticuloendothelial system (RES)] and enhance the targeting capability of the nanoparticles to tumors overexpressing folate receptor (FR). The FRNPs exhibited an average particle size of 301±10.8 nm and surface potential of 39.1±0.43 mV. Subsequently, in vitro, FRNPs labeled with FITC fluorescence dye were visibly uptaken into the cytoplasm of FR-overexpressing cancer cells (Bel7402 and SW620 cells), whereas the A549 cells expressing relatively low levels of FR just bound with few FRNPs. These results demonstrated that FRNPs have a high affinity to FR-overexpressing cancer cells. Additionally, in in vivo experiments, FRNPs achieved a greater enhancement of tumor ultrasound imaging and a longer enhancement time in FR-overexpressing tumors and the Cy7-labeled FRNPs exhibited a relatively high tumor-targeted distribution in FR­overexpressing tumors. Targeted ultrasound and fluorescence imaging revealed that FRNPs have the ability to target FR-overexpressing tumors and ex vivo fluorescence imaging was then used to further verify and confirm the presence of FRNPs in tumor tissues with histological analysis of the tumor slices. On the whole, our data demonstrate that the FRNPs may prove to be a promising candidate for the early diagnosis for FR-overexpressing tumors at the molecular and cellular levels.

Perfluorinated hydroxamic acids are potent and selective inhibitors of HDAC-like enzymes from Pseudomonas aeruginosa.

A series of perfluorinated SAHA (PFSAHA) was prepared and profiled against a panel of human and bacterial members of the Histone deacetylase (HDAC) family. Some of the active substances show nanomolar inhibitory activity and several hundred fold selectivity for the HDAC like enzyme PA3774 from P. aeruginosa. The extraordinary selectivity against human HDACs results from the distinct oligomeric state of PA3774 which consists of two head-to-head dimers. The binding pocket is defined by the surface of both opposite monomers confining the access of ligands to the active site. In addition, the aromatic cap group of PFSAHA undergoes an edge-to-face aromatic interaction with phenylalanine from the opposite monomer.

Rhodium-Catalyzed (Perfluoroalkyl)olefination of Acetanilides Leading to Perfluoroalkylated Aromatics.

We have developed an efficient Rh-catalyzed (perfluoroalkyl)olefination reaction of acetanilides, which provides a versatile synthetic entry to a range of perfluoroalkylated compounds.

Synthesis and Solution Properties of Adamantane Containing Quaternary Ammonium Salt-type Cationic Surfactants: Hydrocarbon-based, Fluorocarbonbased and Bola-type.

Quaternary ammonium salt-type cationic surfactants with an adamantyl group (hydrocarbon-type; CnAdAB, fluorocarbon-type; CmFC3AdAB, bola-type; Ad-s-Ad, where n, m and s represent hydrocarbon chain lengths of 8-16, fluorocarbon chain lengths of 4-8, and spacer chain length of 10-12) were synthesized via quaternization of N, N-dimethylaminoadamantane and n-alkyl bromide or 1, n-dibromoalkane. Conductivity and surface tension were measured to characterize the solution properties of the synthesized adamantyl group-containing cationic surfactants. In addition, the effects of hydrocarbon and fluorocarbon chain lengths and spacer chain length between headgroups on the measured properties were evaluated by comparison with those of conventional cationic surfactants. The critical micelle concentration (CMC) of CnAdAB and Ad-s-Ad was 2/5 of that for the corresponding conventional surfactants CnTAB and bola-type surfactants with similar number of carbons in the alkyl or alkylene chain; this was because of the increased hydrophobicity due to the adamantyl group. A linear relationship between the logarithm of CMC and the hydrocarbon chain length for CnAdAB was observed, as well as for CnTAB. The slope of the linear correlation for both surfactants was almost the same, indicating that the adamantyl group does not affect the CMC with variations in the hydrocarbon chain length. Similar to conventional surfactants CnTAB, the hydrocarbon-type CnAdAB is highly efficient in reducing the surface tension of water, despite the large occupied area per molecule resulting from the relatively bulky structure of the adamantane skeleton. On the other hand, the bola-type Ad-s-Ad resulted in increased surface tension compared to CnAdAB, indicating that the curved chain between adamantyl groups leads to poor adsorption and orientation at the air-water interface.

Regiospecifically Fluorinated Polycyclic Aromatic Hydrocarbons via Julia-Kocienski Olefination and Oxidative Photocyclization. Effect of Fluorine Atom Substitution on Molecular Shape.

A modular synthesis of regiospecifically fluorinated polycyclic aromatic hydrocarbons (PAHs) is described. 1,2-Diarylfluoroalkenes, synthesized via Julia-Kocienski olefination (70-99% yields), were converted to isomeric 5- and 6-fluorobenzo[c]phenanthrene, 5-and 6-fluorochrysene, and 9- and 10-benzo[g]chrysene (66-83% yields) by oxidative photocyclization. Photocyclization to 6-fluorochrysene proceeded more slowly than conversion of 1-styrylnaphthalene to chrysene. Higher fluoroalkene dilution led to a more rapid cyclization. Therefore, photocyclizations were performed at higher dilutions. To evaluate the effect of fluorine atom on molecular shapes, X-ray data for 5- and 6-fluorobenzo[c]phenanthrene, 6-fluorochrysene, 9- and 10-fluorobenzo[g]chrysene, and unfluorinated chrysene as well as benzo[g]chrysene were obtained and compared. The fluorine atom caused a small deviation from planarity in the chrysene series and decreased nonplanarity in the benzo[c]phenanthrene derivatives, but its influence was most pronounced in the benzo[g]chrysene series. A remarkable flattening of the molecule was observed in 9-fluorobenzo[g]chrysene, where the short 2.055 Å interatomic distance between bay-region F-9 and H-8, downfield shift of H-8, and a 26.1 Hz coupling between F-9 and C-8 indicate a possible F-9···H-8 hydrogen bond. In addition, in 9-fluorobenzo[g]chrysene, the stacking distance is short at 3.365 Å and there is an additional interaction between the C-11-H and C-10a of a nearby molecule that is almost perpendicular.

Perspective: 4D ultrafast electron microscopy--Evolutions and revolutions.

In this Perspective, the evolutionary and revolutionary developments of ultrafast electron imaging are overviewed with focus on the "single-electron concept" for probing methodology. From the first electron microscope of Knoll and Ruska [Z. Phys. 78, 318 (1932)], constructed in the 1930s, to aberration-corrected instruments and on, to four-dimensional ultrafast electron microscopy (4D UEM), the developments over eight decades have transformed humans' scope of visualization. The changes in the length and time scales involved are unimaginable, beginning with the micrometer and second domains, and now reaching the space and time dimensions of atoms in matter. With these advances, it has become possible to follow the elementary structural dynamics as it unfolds in real time and to provide the means for visualizing materials behavior and biological functions. The aim is to understand emergent phenomena in complex systems, and 4D UEM is now central for the visualization of elementary processes involved, as illustrated here with examples from past achievements and future outlook.