Pd-Senphos Catalyzed trans-Selective Cyanoboration of 1,3-Enynes.

The first trans-selective cyanoboration reaction of an alkyne, specifically a 1,3-enyne, is described. The reported palladium-catalyzed cyanoboration of 1,3-enynes is site-, regio-, and diastereoselective, and is uniquely enabled by the 1,4-azaborine-based Senphos ligand structure. Tetra-substituted alkenyl nitriles are obtained providing useful boron-dienenitrile building blocks that can be further functionalized. The utility of our method has been demonstrated with the synthesis of Satigrel, an anti-platelet aggregating agent.

Catalytic Carbo- and Aminoboration of Alkenyl Carbonyl Compounds via Five- and Six-Membered Palladacycles.

A palladium(II)-catalyzed alkene difunctionalization reaction has been developed, wherein B2pin2 is used to trap chelation-stabilized alkylpalladium(II) intermediates that are formed upon nucleopalladation. A range of carbon and nitrogen nucleophiles were found to be suitable coupling partners in this transformation, providing moderate to high yields. Both 3-butenoic and 4-pentenoic acid derivatives were reactive substrate classes, affording ß,γ- and γ,δ-difunctionalized carboxylic acid derivatives. This work represents a new strategy to synthesize highly functionalized secondary boronates that complements existing methods.

Self-Assembling Behavior of Glycerol Monoundecenoate in Water.

The self-assembling properties of glycerol esters in water are well known. Still, few data on glycerol monoesters of undecylenic acid are available. The aim of this study was to highlight the behavior of glycerol monoundecenoate (GM-C11:1) in different diluted and concentrated states. Its self-assembling properties in water and upon solid inorganic surfaces were investigated in the diluted state using surface tension experiments, atomic force microscopy, and cryogenic transmission electron microscopy studies. In the concentrated state, the gelling properties in the presence of water were investigated using polarized light microscopy, differential scanning calorimetry (DSC), and small-angle X-ray scattering (SAXS) experiments. GM-C11:1 at 100 mg/L self-assembles at the liquid/air interfaces as aggregates of approximately 20 nm in diameter, organized into concentric forms. These aggregates are spherical globules composed of several molecules of GM-C11:1. At higher concentrations (1000 and 104 mg/L), GM-C11:1 is able to uniformly coat liquid/air and liquid/solid interfaces. In bulk, GM-C11:1 forms spontaneously aggregates and vesicles. In a more concentrated state, GM-C11:1 assembles into lamellar Lß and Lα forms in water. By cross-referencing SAXS and DSC findings, we were able to distinguish between interlamellar water molecules strongly bound to GM-C11:1 and other molecules remaining unbound and considered to be "mobile" water. The percentage of water strongly bound was proportional to the percentage of GM-C11:1 in the system. In this case, GM-C11:1 appears to be an effective molecule for surface treatments for which water retention is important.

Chemical Probes to Directly Profile Palmitoleoylation of Proteins.

Palmitoleoylation is a unique fatty acylation of proteins in which a monounsaturated fatty acid, palmitoleic acid (C16:1), is covalently attached to a protein. Wnt proteins are known to be palmitoleoylated by cis-Δ9 palmitoleate at conserved serine residues. O-palmitoleoylation plays a critical role in regulating Wnt secretion, binding to the receptors, and in the dynamics of Wnt signaling. Therefore, protein palmitoleoylation is important in tissue homeostasis and tumorigenesis. Chemical probes based on saturated fatty acids, such as ω-alkynyl palmitic acid (Alk-14 or Alk-C16 ), have been used to study Wnt palmitoleoylation. However, such probes require prior conversion to the unsaturated fatty acid by stearoyl-CoA desaturase (SCD) in cells, significantly decreasing their selectivity and efficiency for studying protein palmitoleoylation. We synthesized and characterized ω-alkynyl cis- and trans-palmitoleic acids (cis- and trans-Alk-14:1) as chemical probes to directly study protein palmitoleoylation. We found that cis-Alk-14:1 could more efficiently label Wnt proteins in cells. Interestingly, the DHHC family of palmitoyl acyltransferases can charge both saturated and unsaturated fatty acids, potentially using both as acyl donors in protein palmitoylation and palmitoleoylation. Furthermore, proteomic analysis of targets labeled by these probes revealed new cis- and trans-palmitoleoylated proteins. Our studies provided new chemical tools and revealed new insights into palmitoleoylation in cell signaling.

Fluorine in fragrances: exploring the difluoromethylene (CF2) group as a conformational constraint in macrocyclic musk lactones.

The CF2 group is incorporated into specific positions within the lactone ring of the natural musk lactone, (12R)-(+)-12-methyl-13-tridecanolide, a constituent of Angelica root oil, Angelica archangelica L. The approach is taken as it was anticipated that CF2 groups would dictate corner locations in the macrocycle and limit the conformational space available to the lactone. Three fluorine containing lactones are prepared by organic synthesis. One (8) has CF2 groups located at the C-6 and C-9 positions, another (9) with CF2 groups at the C-5 and C-9 positions, and a third (10) with a CF2 group at C-8. Two of the fluorine containing lactones (8 and 10) were sufficiently crystalline to obtain X-ray crystal structures which revealed that the CF2 groups do adopt corner locations. All three lactones were subject to computational analysis at the B3LYP-D3/6-311+G** level to assess the relative energies of different conformers. In all cases, the global minima and most of the lowest energy minima have squared/rectangular geometries and located the CF2 groups at the corners. The lowest energy structures for 8 and 10 closely approximated the observed X-ray structures, suggesting good convergence of theory and experiment in determining relevant low energy conformations. All three compounds retained a pleasant odour suggesting the rings retained sufficient conformational flexibility to access relevant olfactory conformations.

Palladium-catalyzed synthesis of 2-alkenyl-3-arylindoles via a dual α-arylation strategy: formal synthesis of the antilipemic drug fluvastatin.

A new approach has been developed for the synthesis of substituted 2-alkenyl-3-arylindoles. The strategy comprises palladium-catalyzed dual α-arylation of TES-enol ethers of enones as the key step. This methodology results in products with very good yields and the regioselectivity is exclusive. We have also successfully used this dual α-arylation methodology in the formal synthesis of the cholesterol-lowering drug fluvastatin.

Hexadecenoic fatty acid isomers: a chemical biology approach for human plasma biomarker development.

Hexadecenoic fatty acids are monounsaturated lipid components, which are interesting targets of plasma lipidomic studies and biomarker development. The main positional isomers, palmitoleic (9-cis-16:1) and sapienic acids (6-cis-16:1), have an endogenous origin from palmitic acid, the former being recognized as a component of adipose tissue with signaling activity, whereas the latter is mainly reported as a component of sebum. The trans 16:1 isomers are attributed so far to dietary sources of industrial and dairy fats, whereas the endogenous formation due to the free radical-mediated isomerization can represent an emerging, yet unexplored, pathway connected to cellular stress. Herein, we report a chemical biology approach for the development of hexadecenoic fatty acids as plasma biomarkers, with the first synthesis of 6-trans-16:1 and the efficient analytical setup with unambiguous assignment of 16:1 double bond position and geometry, which was applied to human commercial LDL and plasma cholesteryl esters. Sapienic acid was identified together with its geometrical trans isomer for the first time. The quantitation of hexadecenoic fatty acid isomers evidenced their different levels in the two lipid classes and LDL fractions, making us foresee interesting applications to the metabolic evaluation of fatty acid pathways. These findings open new perspectives for plasma lipidomics involving monounsaturated fatty acids, highlighting future developments for their evaluation in different health conditions including free radical stress.

Synthesis and antimalarial and antituberculosis activities of a series of natural and unnatural 4-methoxy-6-styryl-pyran-2-ones, dihydro analogues and photo-dimers.

Previous studies have identified the 3,6-dialkyl-4-hydroxy-pyran-2-one marine microbial metabolites pseudopyronines A and B to be modest growth inhibitors of Mycobacterium tuberculosis and a range of tropical diseases including Plasmodium falciparum and Leishmania donovani. In an effort to expand the structure-activity relationship of this compound class towards infectious diseases, a library of natural product and natural product-like 4-methoxy-6-styryl-pyran-2-ones and a subset of catalytically reduced examples were synthesized. In addition, the photochemical reactivity of several of the 4-methoxy-6-styryl-pyran-2-ones were investigated yielding head-to-head and head-to-tail cyclobutane dimers as well as examples of asymmetric aniba-dimer A-type dimers. All compounds were evaluated for cytotoxicity and activity against M. tuberculosis, P. falciparum, L. donovani, Trypanosoma brucei rhodesiense and Trypanosoma cruzi. Of the styryl-pyranones, natural product 3 and non-natural styrene and naphthalene substituted examples 13, 18, 21, 22 and 23 exhibited antimalarial activity (IC(50) <10 µM) with selectivity indices (SI) >10. Δ(7) Dihydro analogues were typically less active or lacked selectivity. Head-to-head and head-to-tail photodimers 5 and 34 exhibited moderate IC(50)s of 2.3 to 17 µM towards several of the parasitic organisms, while the aniba-dimer-type asymmetric dimers 31 and 33 were identified as being moderately active towards P. falciparum (IC(50) 1.5 and 1.7 µM) with good selectivity (SI ~80). The 4-tert-butyl aniba-dimer A analogue 33 also exhibited activity towards L. donovani (IC(50) 4.5 µM), suggesting further elaboration of this latter scaffold could lead to the identification of new leads for the dual treatment of malaria and leishmaniasis.

Simultaneous determination of parabens and synthetic musks in water by stir-bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry.

This study focuses on a method for simultaneously determining personal care products in a wide range of polarities in different water matrices. The method is based on stir-bar sorptive extraction followed by thermal desorption-gas chromatography-mass spectrometry. Prior to extraction, the parabens were acetylated to improve their affinity for the polydimethylsiloxane phase of the stir bar. The method showed good linearity, repeatability and reproducibility between days for all compounds and limits of detection at low ng/L levels (between 0.02 and 0.3 ng/L). The proposed method is also environmentally friendly, because it does not use organic solvents, and reduces the risk of external pollution, due to the minimal manipulation of the sample required. The method developed was successfully applied for the analysis of personal care products in different kinds of water matrices: influents and effluents of urban and industrial wastewater treatment plants, effluents of a reverse osmosis treatment plant and river waters. The influents of urban treatment plants generally showed the highest values for synthetic musks, with concentrations of up to 2219 ng/L of galaxolide, whereas the highest concentrations of parabens were detected in the industrial treatment plants influents.

Total synthesis and absolute configuration of malyngamide W.

A concise enantioselective synthesis of malyngamide W (1) and its 2'-epimer was described. The strategy was based on three key steps: (1) ozonolysis of compound 11 which was derived from (R)-(-)-carvone 8, followed by copper-iron-catalyzed rearrangement to give the key cyclohex-2-enone intermediate 5, (2) Nozaki-Hiyama-Kishi coupling reaction between aldehyde 4 and iodide 14 to afford alcohol 3, and (3) asymmetric (R)-CBS reduction of the ketone functionality in compound 21 to establish the C-2' chiral center in the target compound 1. The absolute configuration of malyngamide W (1) was thus confirmed via the synthesis of 1 and 2'-epi-1.

Fingolimod (FTY720): a recently approved multiple sclerosis drug based on a fungal secondary metabolite.

Fingolimod (Gilenya; FTY720), a synthetic compound based on the fungal secondary metabolite myriocin (ISP-I), is a potent immunosuppressant that was approved (September 2010) by the U.S. FDA as a new treatment for multiple sclerosis (MS). Fingolimod was synthesized by the research group of Tetsuro Fujita at Kyoto University in 1992 while investigating structure-activity relationships of derivatives of the fungal metabolite ISP-I, isolated from Isaria sinclairii. Fingolimod becomes active in vivo following phosphorylation by sphingosine kinase 2 to form fingolimod-phosphate, which binds to extracellular G protein-coupled receptors, sphingosine 1-phosphates, and prevents the release of lymphocytes from lymphoid tissue. Fingolimod is orally active, which is unique among current first-line MS therapies, and it has the potential to be used in the treatment of organ transplants and cancer. This review highlights the discovery and development of fingolimod, from an isolated lead natural product, through synthetic analogues, to an approved drug.

Facile and highly enantioselective synthesis of (+)- and (-)-fluvastatin and their analogues.

A highly enantioselective synthesis of (+)- and (-)-fluvastatin and their analogues has been facilitated by the reaction of an aldehyde with diketene in the presence of Ti(O-i-Pr)4 and a chiral Schiff base ligand. Either enantiomer of the Schiff base could be employed to obtain (+)- or (-)-fluvastatin. Diastereoselective reductions of the resultant keto moiety of ß-hydroxy ketoesters provided the syn-1,3-diol esters (91% ee), which were subsequently recrystallized and saponified to afford (+)- and (-)-fluvastatin in >99.9% ee.

Trans-palmitoleic acid (trans-9-C16:1, or trans-C16:1 n-7): Nutritional impacts, metabolism, origin, compositional data, analytical methods and chemical synthesis. A review.

Since the early 2010s, dietary trans-palmitoleic acid (trans-9-hexadecenoic acid, trans-9-C16:1 in the Δ-nomenclature, trans-C16:1 n-7 in the Ω-nomenclature, TPA) has been epidemiologically associated with a lower risk of type 2 diabetes in humans. Thanks to these findings, TPA has become a nutrient of interest. However, there is a lot of unresolved crucial questions about this dietary fatty acid. Is TPA a natural trans fatty acid? What kind of foods ensures intakes in TPA? What about its metabolism? How does dietary TPA act to prevent type 2 diabetes? What are the biological mechanisms involved in this physiological effect? Clearly, it is high time to answer all these questions with the very first review specifically dedicated to this intriguing fatty acid. Aiming at getting an overview, we shall try to give an answer to all these questions, relying on appropriate and accurate scientific results. Briefly, this review underlines that TPA is indeed a natural trans fatty acid which is metabolically linked to other well-known natural trans fatty acids. Knowledge on physiological impacts of dietary TPA is limited so far to epidemiological data, awaiting for supplementation studies. In this multidisciplinary review, we also emphasize on methodological topics related to TPA, particularly when it comes to the quantification of TPA in foods and human plasma. As a conclusion, we highlight promising health benefits of dietary TPA; however, there is a strong lack in well-designed studies in both the nutritional and the analytical area.

Axial shielding of Pd(II) complexes enables perfect stereoretention in Suzuki-Miyaura cross-coupling of Csp3 boronic acids.

Stereocontrolled Csp3 cross-coupling can fundamentally change the types of chemical structures that can be mined for molecular functions. Although considerable progress in achieving the targeted chemical reactivity has been made, controlling stereochemistry in Csp3 cross-coupling remains challenging. Here we report that ligand-based axial shielding of Pd(II) complexes enables Suzuki-Miyaura cross-coupling of unactivated Csp3 boronic acids with perfect stereoretention. This approach leverages key differences in spatial orientation between competing pathways for stereoretentive and stereoinvertive transmetalation of Csp3 boronic acids to Pd(II). We show that axial shielding enables perfectly stereoretentive cross-coupling with a range of unactivated secondary Csp3 boronic acids, as well as the stereocontrolled synthesis of xylarinic acid B and all of its Csp3 stereoisomers. We expect these ligand design principles will broadly enable the continued search for practical and effective methods for stereospecific Csp3 cross-coupling.

Construction of Quaternary Carbon Stereocenter of α-Tertiary Amine through Remote C-H Functionalization of Tris Derivatives: Enantioselective Total Synthesis of Myriocin.

We describe the development of a strategy for the construction of the quaternary carbon stereocenter of α-tertiary amines. This strategy highlights a site-selective C-H functionalization involving an alkoxy-radical-triggered 1,5-hydrogen transfer (1,5-HAT) reaction of a conformationally fixed spiro-compound derived from trishydroxymethylaminomethane (Tris). The utilization of this strategy enabled an enantioselective total synthesis of myriocin, a naturally occurring sphingosine analog that displays potent immunosuppressive activity.

Targeting EZH2 for glioma therapy with a novel nanoparticle-siRNA complex.

BACKGROUND: For the past few years, gene-therapy has recently shown considerable clinical benefit in cancer therapy, and the applications of gene therapies in cancer treatments continue to increase perennially. EZH2, an ideal candidate for tumor gene therapy, plays an important role in the tumorigenesis. METHODS: In this study, we developed a novel gene delivery system with a self-assembly method by Methoxy polyethylene glycol-polycaprolactone (MPEG-PCL) and DOTAP(DMC). And EZH2si-DMC was used to research anti-glioma both in vitro and in vivo. RESULTS: DMC with zeta-potential value of 36.7 mV and size of 35.6 nm showed good performance in the delivery siRNA to glioma cell in vitro with high 98% transfection efficiency. EZH2si-DMC showed good anti-glioma effect in vitro through inducing cell apoptosis and inhibiting cell growth. What's more, treatment of tumor-bearing mice with DMC-EZH2si complex had significantly inhibited tumor growth at the subcutaneous model in vivo by inhibiting EZH2 protein expression, promoting apoptosis and reducing proliferation. CONCLUSION: The EZH2 siRNA and DMC complex may be used to treat the glioma in clinical as a new drug.

An improved asymmetric synthesis of malyngamide U and its 2'-epimer.

An accelerated and improved asymmetric synthesis of malyngamide U (1) and its 2'-epimer (2'-epi-1) was accomplished from readily available n-hexanal, ethanolamine and (R)-(-)-carvone. The key steps involved a Johnson-Claisen rearrangement in the synthesis of an unsaturated carboxylic acid 4 and an aldol reaction in the construction of the skeleton of 1 and 2'-epi-1. There are 13 steps in the synthesis, with a 2.7% overall yield for 1 and a 0.4% yield for 2'-epi-1.

Engineering of budesonide-loaded lipid-polymer hybrid nanoparticles using a quality-by-design approach.

Chronic obstructive pulmonary disease (COPD) is a complex disease, characterized by persistent airflow limitation and chronic inflammation. The purpose of this study was to design lipid-polymer hybrid nanoparticles (LPNs) loaded with the corticosteroid, budesonide, which could potentially be combined with small interfering RNA (siRNA) for COPD management. Here, we prepared LPNs based on the biodegradable polymer poly(dl-lactic-co-glycolic acid) (PLGA) and the cationic lipid dioleyltrimethylammonium propane (DOTAP) using a double emulsion solvent evaporation method. A quality-by-design (QbD) approach was adopted to define the optimal formulation parameters. The quality target product profile (QTPP) of the LPNs was identified based on risk assessment. Two critical formulation parameters (CFPs) were identified, including the theoretical budesonide loading and the theoretical DOTAP loading. The CFPs were linked to critical quality attributes (CQAs), which included the intensity-based hydrodynamic particle diameter (z-average), the polydispersity index (PDI), the zeta-potential, the budesonide encapsulation efficiency, the actual budesonide loading and the DOTAP encapsulation efficiency. A response surface methodology (RSM) was applied for the experimental design to evaluate the influence of the CFPs on the CQAs, and to identify the optimal operation space (OOS). All nanoparticle dispersions displayed monodisperse size distributions (PDI<0.2) with z-averages of approximately 150nm, suggesting that the size is not dependent on the investigated CFPs. In contrast, the zeta-potential was highly dependent on the theoretical DOTAP loading. Upon increased DOTAP loading, the zeta-potential reached a maximal point, after which it remained stable at the maximum value. This suggests that the LPN surface is covered by DOTAP, and that the DOTAP loading is saturable. The actual budesonide loading of the LPNs was mainly dependent on the initial amount of budesonide, and a clear positive effect was observed, which shows that the interaction between drug and PLGA increases when increasing the initial amount of budesonide. The OOS was modeled by applying the QTPP. The OOS had a budesonide encapsulation efficiency higher than 30%, a budesonide loading above 15µg budesonide/mg PLGA, a zeta-potential higher than 35mV and a DOTAP encapsulation efficiency above 50%. This study shows the importance of systematic formulation design for understanding the effect of formulation parameters on the characteristics of LPNs, eventually resulting in the identification of an OOS.

Facile stereospecific synthesis and biological evaluation of (S)- and (R)-2-amino-2-methyl-4-[123I]iodo-3-(E)-butenoic acid for brain tumor imaging with single photon emission computerized tomography.

Both enantiomers of 2-amino-2-methyl-4-iodo-3-(E)-butenoic acid (IVAIB, 5) were radioiodoinated in 65-72% yield. (S)-IVAIB entered 9L gliosarcoma cells primarily via A-type transport in vitro with higher uptake than (R)-IVAIB. Biodistribution studies in rats with 9L gliosarcoma brain tumors demonstrated higher tumor to brain ratios with (S)-IVAIB (75:1 at 1 h) than (R)-IVAIB (7.7:1). In this model, (S)-IVAIB is superior to (R)-IVAIB and is a promising radiotracer for brain tumor imaging.