The Biomimetic Synthesis of Polyarylated Fluorenes, Relevant to Selaginellaceae Polyphenols, Leading to the Spontaneous Formation of Stable Radicals.

This work reports a biomimetic synthesis of polyarylated fluorene derivatives. The molecules are formed via intramolecular electrophilic aromatic substitution, resembling a cyclization leading towards the natural selaginpulvilins from selaginellins. The scope of the reaction was investigated, and the products were obtained in 60-95 % yields. Some of the compounds decompose to a stable radical. We investigated the nature and the origin of the radical using experimental methods, including EPR or electrochemical measurements, as well as theoretical methods, such as DFT calculations. Based on our observations, we hypothesize, that phenoxy radicals are formed in the first instance, which however undergo internal rearrangement to thermodynamically more stable carbon-centered radicals. The preliminary data also show the cytotoxic properties of some of the molecules.

Cyclopentadienyl Molybdenum(II) Compounds Bearing Ether and Thioether Functions in the Side Chain: Synthesis, Characterization, and Cytotoxic/Cytostatic Studies.

A series of molybdenum(II) compounds [(η5 -Cp')Mo(CO)2 (L2 )][BF4 ] (Cp'=C5 H4 (CH2 )2 SPh, C9 H6 (CH2 )2 OMe, L2= N,N-chelating ligand) have been synthesized and characterized by spectroscopic and analytical methods including X-ray crystallography. The in vitro assay on human leukemia cells MOLT-4 has shown that the substitution in the π-ligand in combination with suitable N,N-chelating ligand can lead to species with cytotoxicity considerably higher than reported to cisplatin. Unusually high activity was observed for compounds bearing phenanthroline ligands [{η5 -C9 H6 (CH2 )2 OMe}Mo(CO)2 (3,4,7,8-Me4 phen)][BF4 ] (IC50 =0.7±0.3 µM) and [{η5 -C9 H6 (CH2 )2 OMe}Mo(CO)2 (4,7-Ph2 phen)][BF4 ] (IC50 values 0.8±0.4 µM).

Synthesis of fused 1,2-naphthoquinones with cytotoxic activity using a one-pot three-step reaction.

A method for the synthesis of fused 1,2-naphthoquinones, as analogues of biologically active natural terpene quinones, is described. The intermediate polycyclic naphthalenes were prepared by a one-pot palladium-catalysed process from simple alkynes, one of which was made from an optically pure biomass-derived levoglucosenone. The prepared methoxy-substituted naphthalenes were subsequently transformed in one step to 1,2-naphthoquinones by a trivalent-iodine-mediated oxidation. The naphthoquinone products were found to have cytotoxic properties.

NMR Structure Elucidation of Naphthoquinones from Quambalaria cyanescens.

Naphthoquinones isolated from Quambalaria cyanescens (quambalarines) are natural pigments possessing significant cytotoxic and antimicrobial properties. Determining the structure of naphthoquinone compounds is important for the understanding of their biological activities and the informed synthesis of related analogues. Identifying quambalarines is challenging, because they contain a hydroxylated naphthoquinone scaffold and have limited solubility. Here, we report a detailed structural study of quambalarine derivatives, which form strong intramolecular hydrogen bonds (IMHBs) that enable the formation of several tautomers; these tautomers may complicate structural investigation due to their fast interconversion. To investigate tautomeric equilibria and identify new quambalarines, we complemented the experimental NMR spectroscopy data with density functional theory (DFT) calculations.

Enhanced cytotoxicity of indenyl molybdenum(ii) compounds bearing a thiophene function.

A series of six indenyl molybdenum compounds bearing a thiophenyl function in the side chain were prepared and characterized by analytical and spectroscopic methods. The structures of [(η5-C9H6CH2C4H3S)(η3-C3H5)Mo(CO)2] and [(η5-C9H6CH2C4H3S)Mo(CO)2(bpy)][BF4] were determined by single-crystal X-ray diffraction. The compounds bearing N,N-chelating ligands exhibit increased cytotoxic activity against human leukemia cell lines MOLT-4; up to two orders of magnitude lower IC50 values were observed compared to analogues with unsubstituted indenyl, which clearly demonstrates the strong effect of the indenyl ligand modification on the biological activity of the molybdenum(ii) compounds. The highest cytostatic potential was observed for the complex bearing 4,7-diphenyl-1,10-phenanthtoline [(η5-C9H6CH2C4H3S)Mo(CO)2(Ph2phen)][BF4] with IC50 (MOLT-4) = 0.19 ± 0.02 µM. Detailed regulation of the molecular and cellular mechanism by this derivative was investigated on the lung carcinoma cell line A549 and compared with the lung fibroblast cell line MRC-5. Rather unusual differences in the effects on tumor and non-tumor cell lines provide a unique insight into the cytostatic action of molybdenum(ii) complexes.

Polymorphic Transformation of Drugs Induced by Glycopolymeric Vesicles Designed for Anticancer Therapy Probed by Solid-State NMR Spectroscopy.

Understanding the nature of the drug-polymer interactions in micellar drug delivery systems and what happens with the drug and the polymer once the complex has formed is essential for the rational design of the polymeric matrices suitable for a particular drug. In this work, glycopolymeric vesicles-a block copolymer, poly(1-O-methacryloyl-ß-d-fructopyranose)-b-poly(methyl methacrylate), (PFru36-PMMA160),-designed to target tumor cells loaded with two drugs, ellipticine and curcumin, were characterized. Advanced solid-state NMR spectroscopy and single-crystal/powder X-ray diffraction (XRD) combined with CASTEP calculations shed light on the nature of the drug, the polymer, and their interactions. While the low drug loading (ca. 5%) ensured that the structure, size, and shape of the polymeric vesicles did not change significantly, the solid-state forms of the drugs changed markedly. Upon loading into the vesicles, ellipticine favored a highly ordered form distinctly different from the bulk drug as indicated by 13C solid-state NMR spectroscopy. A detailed analysis of the CASTEP-calculated 13C spectra derived from crystallographic data based on the lowest mean absolute error showed the best match with form I. Moreover, ellipticine before loading was found as a new polymorph and was described by single-crystal XRD as a new orthorhombic Form III. Likewise, curcumin, originally present in monoclinic Form I was found to recrystallize as metastable orthorhombic Form II inside the vesicles. Intermolecular interactions between the polymeric vesicles and the drugs, ellipticine as well as curcumin, were detected using 2D 1H magic angle spinning experiments, indicating that the drugs are localized in the hydrophobic layer of the vesicles.

Vanadocene complexes bearing N,N'-chelating ligands: Synthesis, structures and in vitro cytotoxic studies on the A549 lung adenocarcinoma cell line.

Ten new vanadocene complexes bearing N,N'-chelating ligands were prepared, characterized, and their cytotoxicity toward a panel of cancer cells was measured. Structures of four vanadocene compounds were determined by single crystal X-ray diffraction analysis. Complexes containing 1,2-bis(phenylimino)acenaphthene (bian) and 1,2-bis(4-methoxyphenylimino)acenaphthene (4-MeO-bian) exhibit higher cytotoxicity than those with dipyrido[3,2-a:2',3'-c]phenazine (dppz) and (E)-N-((pyridin-2-yl)methylene)benzenamine (pyma). In light of the finding, cytotoxic mechanisms of two highly effective complexes [(η5-C5H4Me)2V(bian)][OTf]2 (3b) and [(η5-C5H4Me)2V(4-MeO-bian)][OTf]2 (4b) against human A549 lung adenocarcinoma cells were investigated by following membrane leakage of intracellular lactate dehydrogenase, Trypan Blue staining and activation of tumor protein p53 (p53). Evaluated complexes have a potent dose-dependent antiproliferative activity, causing cell cycle redistribution by the increased accumulation of cells in the G2 and S phase. In accord with the observed cell cycle deceleration, cyclin-dependent kinase inhibitor-interacting protein 1 (p21WAF1/Cip1), extracellular signal-regulated kinases 1 and 2 (ERK1/2), Checkpoint kinase 1 (Chk1), Checkpoint kinase 2 (Chk2) and their phosphorylated forms Chk1 at serine 345 and Chk2 at threonine 68 increased. In the cells exposed to complexes, dose- and time-dependent apoptotic process is initiated by the activation of the initiator caspase 8, followed by activation of effector caspase 3/7 and phosphatidylserine externalization. Moreover, because of treatment, A549 cells activate prosurvival mitogen-activated protein kinases (MAPK) signaling and up-regulate antiapoptotic protein B-cell lymphoma (Bcl-2), thereby promoting evasion of cell death. Both complexes exhibited considerably higher cytotoxic effect than the reference anticancer drug cis-platin and the cytotoxicity was more pronounced at higher treatment time.

Paramagnetic 19F Relaxation Enhancement in Nickel(II) Complexes of N-Trifluoroethyl Cyclam Derivatives and Cell Labeling for 19F MRI.

1,8-Bis(2,2,2-trifluoroethyl)cyclam (te2f) derivatives with two coordinating pendant arms involving methylenecarboxylic acid (H2te2f2a), methylenephosphonic acid (H4te2f2p), (2-pyridyl)methyl (te2f2py), and 2-aminoethyl arms (te2f2ae) in 4,11-positions were prepared, and their nickel(II) complexes were investigated as possible 19F MR tracers. The solid-state structures of several synthetic intermediates, ligands, and all complexes were confirmed by X-ray diffraction analysis. The average Ni···F distances were determined to be about 5.2 Å. All complexes exhibit a trans-III cyclam conformation with pendant arms bound in the apical positions. Kinetic inertness of the complexes is increased in the ligand order te2f2ae ≪ te2f < te2f2py ≈ H4te2f2p ≪ H2te2f2a. The [Ni(te2f2a)] complex is the most kinetically inert Ni(II) complex reported so far. Paramagnetic divalent nickel caused a shortening of 19F NMR relaxation time down to the millisecond range. Solubility, stability, and cell toxicity were only satisfactory for the [Ni(te2f2p)]2- complex. This complex was visualized by 19F MRI utilizing an ultrashort echo time (UTE) imaging pulse sequence, which led to an increase in sensitivity gain. Mesenchymal stem cells were successfully loaded with the complex (up to 0.925/5.55 pg Ni/F per cell).19F MRI using a UTE pulse sequence provided images with a good signal-to-noise ratio within the measurement time, as short as tens of minutes. The data thus proved a major sensitivity gain in 19F MRI achieved by utilization of the paramagnetic (transition) metal complex as 19F MR tracers coupled with the optimal fast imaging protocol.

Synthesis and in vitro cytotoxicity of acetylated 3-fluoro, 4-fluoro and 3,4-difluoro analogs of D-glucosamine and D-galactosamine.

BACKGROUND: Derivatives of D-glucosamine and D-galactosamine represent an important family of the cell surface glycan components and their fluorinated analogs found use as metabolic inhibitors of complex glycan biosynthesis, or as probes for the study of protein-carbohydrate interactions. This work is focused on the synthesis of acetylated 3-deoxy-3-fluoro, 4-deoxy-4-fluoro and 3,4-dideoxy-3,4-difluoro analogs of D-glucosamine and D-galactosamine via 1,6-anhydrohexopyranose chemistry. Moreover, the cytotoxicity of the target compounds towards selected cancer cells is determined. RESULTS: Introduction of fluorine at C-3 was achieved by the reaction of 1,6-anhydro-2-azido-2-deoxy-4-O-benzyl-ß-D-glucopyranose or its 4-fluoro analog with DAST. The retention of configuration in this reaction is discussed. Fluorine at C-4 was installed by the reaction of 1,6:2,3-dianhydro-ß-D-talopyranose with DAST, or by fluoridolysis of 1,6:3,4-dianhydro-2-azido-ß-D-galactopyranose with KHF2. The amino group was introduced and masked as an azide in the synthesis. The 1-O-deacetylated 3-fluoro and 4-fluoro analogs of acetylated D-galactosamine inhibited proliferation of the human prostate cancer cell line PC-3 more than cisplatin and 5-fluorouracil (IC50 28 ± 3 µM and 54 ± 5 µM, respectively). CONCLUSION: A complete series of acetylated 3-fluoro, 4-fluoro and 3,4-difluoro analogs of D-glucosamine and D-galactosamine is now accessible by 1,6-anhydrohexopyranose chemistry. Intermediate fluorinated 1,6-anhydro-2-azido-hexopyranoses have potential as synthons in oligosaccharide assembly.

Nickel(II) complexes of N-CH2CF3 cyclam derivatives as contrast agents for (19)F magnetic resonance imaging.

Kinetically inert Ni(ii) complexes of N(1),N(8)-bis(2,2,2-trifluoroethyl)cyclams with hydrogen atoms or phosphonic acid groups in the N(4),N(11)-positions show significant (19)F NMR relaxation rate enhancement useful for 19-fluorine MRI imaging.

Alpha (α-) and beta (ß-carboranyl-C-deoxyribosides: syntheses, structures and biological evaluation.

The syntheses of the unprotected neutral closo-carboranyl-C-deoxyriboses, starting from anomeric mixture of 1-ethynyldeoxyriboses, and their corresponding open-cage nido-derivatives have been described. The structures of both the α- and ß-anomers were confirmed by single-crystal X-ray diffraction. While limited water solubility of the neutral closo-anomers led to high cytotoxicity, their cesium salts (nido-species) exhibited higher water solubility leading to lower cytotoxicity. However, in vitro boron neutron capture therapy (BNCT) investigation using the murine squamous cell carcinoma (SCCVII) cell lines showed that there are no significant differences between the survival fractions of the two species.

Asymmetric domino aza-Michael addition/[3 + 2] cycloaddition reactions as a versatile approach to α,ß,γ-triamino acid derivatives.

Nonproteinogenic amino acids are prepared by an unprecedented domino aza-Michael addition-1,3-dipolar cycloaddition, leading to enantiopure highly substituted pyrrolidinopyrazolines. Nonaflyl azide serves as highly effective diazo transfer reagent, forming the link between the conjugate addition and cycloaddition steps. The resulting pyrrolidinopyrazolines can be rapidly transformed to either α,ß,γ-triamino acids or 3,4-methano-ß-prolines. Peptide coupling can be regioselectively conducted at each of the amino groups.

Rational design of chemical ligands for selective mitochondrial targeting.

The rational design of molecules with selective intracellular targeting is a great challenge for contemporary chemistry and life sciences. Here, we demonstrate a rational approach to development of compartment-specific fluorescent dyes from the γ-aryl substituted pentamethine family. These novel dyes exhibit an extraordinary affinity and selectivity for cardiolipin in inner mitochondrial membrane and possess excellent photostability, fluorescent properties, and low phototoxicity. Selective imaging of live and fixed mitochondria was achieved in various cell lines using nanomolar concentrations of these dyes. Their high localization specificity and low toxicity enables study of morphological changes, structural complexity, and dynamics of mitochondria playing a pivotal role in many pathological diseases. These far-red emitting dyes could also serve in a variety of biomedical applications.

Tri-µ-chlorido-bis-[(η-hexa-methyl-benzene)-ruthenium(II)] tetra-chlorido-ferrate(III).

The mol-ecular geometry of the complex cation in the title structure, [(µ-Cl)(3){Ru(II)(η(6)-C(6)Me(6))}(2)][Fe(III)Cl(4)], compares very well with that reported earlier for the corresponding PF(6) (-) salt [Pandey et al. (1999 ▶). J. Organomet. Chem.592, 278-282]. The [FeCl(4)](-) counter ion has a rather regular tetra-hedral geometry with Fe-Cl distances and Cl-Fe-Cl angles in the range 2.1891 (7)-2.2018 (8) Šand 107.10 (3)-110.56 (3)°, respectively. There are no significant inter-molecular inter-actions in the crystal except for some weak C-H⋯Cl contacts, which in turn indicates that the crystal packing is determined predominantly by electrostatic inter-actions between the ionic constituents.

Synthesis and characterisation of Dewar benzene-ferrocene conjugates.

The first Dewar benzene-ferrocene conjugates were synthesised by the reaction of tetraalkylcyclobutadiene-AlCl(3) complexes with 3-ferrocenylpropynoates. Owing to extensive delocalisation, these conjugates feature unusually high thermal and chemical stability, rearranging to their corresponding phenylferrocenes (benzenes) under forcing microwave irradiation conditions.

Metallacarboranes as building blocks for polyanionic polyarmed aryl-ether materials.

Polyanionic species have been obtained in high yield by a new route in the ring-opening reaction of cyclic oxonium [3,3'-Co(8-C4H8O2-1,2-C2B9H10)(1',2'-C2B9H11)] (2) by using carboxylic acids, Grignard reagents, and thiocarboranes as nucleophiles. The crystal structures of Na3(H2O)(C2H5OH)[1'',3'',5''-{3,3'-Co(8-O(CH2CH2O)2-1,2-C2B9H10)(1',2'-C2B9H11)}3-C6H3] and Na(H2O)[3,3'-Co(8-O(CH2CH2O)2C(O)CH3-1,2-C2B9H10)(1',2'-C2B9H11)] show that the chain contributes three or two oxygen atoms for coordination to Na(+), and interestingly, the [3,3'-Co(1,2-C2B9H11)2](-) moiety provides extra B-H coordination sites. These B-H...Na interactions in the solid state have also been confirmed by dynamic NMR studies in solution. These new polyanionic compounds that contain multiple carborane or metallacarborane clusters at their periphery may prove useful as new classes of boron neutron capture therapy compounds with enhanced water solubility and as a core to make a new class of dendrimers.

Optical sensing of sulfate by polymethinium salt receptors: colorimetric sensor for heparin.

Polymethinium salts based on substituted malondialdehyde have been prepared; the salt with PEG substitution showed high selectivity for sulfate anions and heparin in aqueous medium at physiological condition; intracellular imaging of heparin-rich subcellular compartments was achieved with our polymethinium novel receptor for cancer cell lines.

Investigation of vanadocene(IV) alpha-amino acid complexes: synthesis, structure, and behavior in physiological solutions, human plasma, and blood.

This work is focused on investigating the interaction of antitumor active metallocene vanadocene dichloride (Cp2VCl2) and amino acids in aqueous solution at physiological pH. Sixteen vanadocene amino acid complexes [Cp2V(aa)][X] (aa = gly, ala, val, leu, ile, phe, his, and trp; X = Cl, PF6) were prepared and characterized on the basis of spectral measurements (EPR, MS, IR, Raman). Amino acids are coordinated to the vanadocene fragment through the oxygen atom of the carboxylic group and the nitrogen of the amino group, resulting in a five-membered chelate ring. Complexes [Cp2V(val)][PF6] and [Cp2V(ile)][PF6] have been characterized by X-ray structure analyses. It was evidenced that all prepared complexes are stable in both aqueous solutions with physiological pH and in therapeutic NaCl solutions. EPR spectra of vanadocene amino acid complexes in Krebs-Ringer solution in human blood plasma and in whole blood showed that these complexes react with the hydrogen carbonate anion present forming complex Cp2V(O2CO).

Ferrocene-modified purines as potential electrochemical markers: synthesis, crystal structures, electrochemistry and cytostatic activity of (ferrocenylethynyl)- and (ferrocenylethyl)purines.

Palladium-catalyzed Sonogashira cross-coupling reactions of halopurines 9-benzyl-6-chloropurine (2 a), 9-benzyl-8-bromoadenine (2 b), and 9-benzyl-2-chloroadenine (2 c) with ethynylferrocene (1) gave the corresponding (ferrocenylethynyl)purines 3 a-c in moderate to good yields. Catalytic hydrogenation of these alkynes over Pd/C afforded the respective saturated [2-(ferrocenyl)ethyl]purines 4 a-c. The crystal structures 3 a, 3 b, 4 a and 4 b as determined by X-ray diffraction show interesting solid-state interactions, markedly different for purines 3 a and 4 a on one hand and adenines 3 b and 4 b that possess a free amino group on the other. Electrochemistry of electrochemically labelled purines 3 and 4 has been studied by voltammetry and cyclic voltammetry on platinum disc electrode and the experimental oxidation potentials were confirmed and explained by ionization potentials from theoretical DFT calculations. Several compounds of this series exhibited a considerable cytostatic effect.