Modified cyclodextrin polymers as selective ion carriers for Pb(II) separation across plasticized membranes

In the present work the hydrophobic β-cyclodextrin (β-CD) polymers have been used as macrocyclic ion carriers for separation of Pb(II), Zn(II), and Cu(II) ions from dilute aqueous solutions by transport across polymer inclusion membranes. The β-CD polymers were prepared by cross-linking of β-CD with 2-(1-docosenyl)-succinic anhydride derivatives in anhydrous N,N-dimethylformamide in the presence of NaH. The metal ions were transported from aqueous solutions containing heavy metal ions through plasticizer triacetate membranes with dimer and polymer β-CD derivatives into distilled water. The selectivity of lead(II) over other metal ions in the transport through polymer inclusion membrane was very high, especially for dimer cyclodextrin carrier. In the case of competitive transport of Pb(II), Cu(II), and Zn(II) ions through plasticized immobilized membranes the selectivity of process is controlled via formation of ion pairs of β-CD hydroxyl groups with metal cations. The polymer and dimer of β-CD linked by 2-(1-docosenyl)-derivative used as ionic carriers for competitive transport of metal ions show preferential selectivity order: Pb(II)  Cu(II) > Zn(II). Application of ion carriers mixtures (β-CD polymers and palmitic acid) causes the increase of Pb(II) maximal removal from dilute aqueous solution. The weight-average molecular weight (M_W) and the chemical structure of the β-CD polymers were determined using high-performance size exclusion chromatography with refractive index detector, and ¹H NMR spectroscopy.     

Extraction of rare earth elements with organophosphorus extractants as carriers in supported liquid membranes

The membrane extraction of Y, Ce, Eu, Tm and their binary mixtures Ce–Y, Ce–Eu, Ce–Tm with supported liquid membranes containing TBP and HDEHP as carriers in decanedodecane hydrocarbon solvent, has been studied. Upon extraction with TBP aqueous nitrate solutions of rare earth elements (REE) were used as feed phase. In some cases they also contained EDTA or DCTA. In most cases, the receiving phase was an aqueous solution of EDTA. Extraction with HDEHP was performed from nitrate and chloride solutions and the receiving phase was the corresponding dilute acid. Pertraction of an element through a membrane was studied as a function of time and of initial composition of phases. The results are presented in the following forms: flux of metal through membrane, coefficients of permeability, separation factors and effective diffusion coefficients.     

Comparison of carrier-facilitated copper(II) ion transport mechanisms in a supported liquid membrane and in a plasticized cellulose triacetate membrane

Transport of copper ions through a plasticized cellulose triacetate membrane containing lauric acid as carrier and tris(2-ethylhexyl)phosphate (TEHP) as plasticizer has been investigated. A comparative study of transport mechanism across such a membrane and a supported liquid membrane (SLM) containing the same carrier in THEP has been made. In both cases, transport mechanisms were controlled by the diffusion of 1:2 metal/carrier complex in the membrane and of copper ions through the aqueous diffusion layer at the source/membrane interface. Diffusion coefficient in the cellulose triacetate membrane, after normalization, was found to be 22 times lower than in the corresponding SLM.     

Online recovery of radiocesium from soil,cellulose and plant samples by supercritical fluid extraction employing crown ethers and calix-crown derivatives as extractants

Two crown ethers (CEs) viz. dibenzo18crown6, and dibenzo12crown7 and three calix-crown derivatives viz. (octyloxy)calix[4]arene-mono-crown-6 (CMC), calix[4]arene-bis(o-benzocrown-6) (CBC), and calix[4]arene-bis(naphthocrown-6) (CNC) were evaluated for the recovery of ¹³⁷Cs from synthetic soil, cellulose (tissue paper), and plant samples by supercritical fluid extraction (SFE) route. CEs showed poor extraction of ¹³⁷Cs from soil matrix. SFE experiments using 1 × 10^?3 M solutions of CMC, CBC and CNC in acetonitrile at 3 M HNO₃ as modifiers displayed better extraction of ¹³⁷Cs, viz. 21(±2) % (CMC), 16.5(±3) % (CBC), and 4(±1) % (CNC). It was not possible to recover ¹³⁷Cs quantitatively from soil matrix. The inefficient extraction of ¹³⁷Cs from soil matrix was attributed to its incorporation into the interstitial sites. Experiments on tissue papers using CMC showed near quantitative ¹³⁷Cs recovery. On the other hand, recovery from plant samples varied between 50(±5) % (for stems) and 75(±5) % (for leaves).     

Design,synthesis and biological evaluation of O-linked indoles as VEGFR-2 kinase inhibitors (I)

Inhibition of VEGFR-2 signaling pathway has already become one of the most promising approaches for the treatment of cancer. In this study, we describe the design, synthesis, and biological evaluation of a series of O-linked indoles as potent inhibitors of VEGFR-2. Among these compounds, 18 showed significant anti-angiogenesis activities via VEGFR-2 in enzymatic proliferation assays, with IC₅₀ value of 3.8 nmol/L. Kinase selectivity profiling revealed that 18 was a multitargeted inhibitor, and it also exhibited good potency against VEGFR-1, PDGFR-α and β.     

Use of 2-(methoxycarbonyl)phenyllead triacetate in lactone synthesis

Reactions of 2-(methoxycarbonyl)phenyllead triacetate with β-oxo lactones and phenols in the presence of pyridine afforded polycyclic lactones in good yields. A one-pot three-step synthesis without isolation of intermediate products was developed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1554–1557, September, 2006.     

Elaboration and characterisation of a plasticized cellulose triacetate membrane containing trioctylphosphine oxyde (TOPO): Application to the transport of uranium and molybdenum ions

A cellulose triacetate (CTA) membrane containing trioctylphosphine oxyde (TOPO) as carrier and 2-nitrophenyloctyl ether (NPOE) as a plasticizer was prepared. The membrane CTA + NPOE + TOPO was characterised using chemical techniques as well as Fourier Transform InfraRed (FTIR) spectroscopy, X-ray diffraction and Scanning Electron Microscopy (SEM). The CTA membrane is characterised by well-defined pores; these pores are completely filled with the NPOE and carrier. Surfaces of membranes with TOPO are smooth. The systems constituted by the mixture of CTA + NPOE, CTA + NPOE + TOPO do not give any diffraction. This can be due to the absence of crystallization within the membrane. On the other hand, this result should be attributable to the amorphous state of the structure, which permits us to eliminate the mechanism of transfer of the ions by electron jump. A comparative study of transport across a polymer inclusion membrane (PIM) and a supported liquid membrane (SLM) containing the same carrier in chloroform has shown that uranium or molybdenum transport efficiency was increased using PIM instead of SLM. PIM showed higher stability than SLM, the flux of transport remain constant in the former case after 2 weeks.     

Design,synthesis and biological evaluation of 3,4-dihydronaphthalen-1(2H)-one derivatives as Bcl-2 inhibitors

Research on Chemical Intermediates - A series of new 3,4-dihydronaphthalen-1(2H)-one derivatives (6a–f) were designed, and synthesized by the Claisen–Schmidt condensation reaction....     

Design, synthesis and in vitro evaluation of phenylbenzamidine derivatives as SSRIs

A series of phenylbenzamidine analogs were synthesized and tested for their biological activities of inhibiting the reuptake of 5- HT. All of them were new compounds, and their structures were confirmed by 1HNMR, MS and XRD.     

Sulfonyl-bridged oligo(benzoic acid)s: synthesis, X-ray structures, and properties as metal extractants

Sulfonyl-bridged oligo(benzoic acid)s 7 _n (n = 2–4) are prepared from the corresponding triflate esters (8 _n ) of sulfur-bridged oligophenols by palladium-catalyzed methoxycarbonylation of the triflate moieties, followed by hydrolysis of the resulting methyl esters, and subsequent oxidation of the sulfur bridges. X-ray analysis reveals that dimer 7 ₂ forms supramolecular zig-zag chains through intermolecular hydrogen bonds between the carboxy groups. As for the crystal of trimer 7 ₃ , two molecules are associated through two couples of intermolecular hydrogen bonds between terminal and central carboxy groups to form a cyclic dimer, which connects with two adjacent dimers with the remaining carboxy groups to construct an infinite columnar structure. Tetramer 7 ₄ adopts a monomolecular cyclic structure through intramolecular hydrogen bonds between the terminal carboxy groups, and a molecule connects with each of two adjacent molecules through two couples of intermolecular hydrogen bonds between inner carboxy and sulfonyl groups. Solvent extraction experiments reveal that the oligo(benzoic acid)s exhibit high extractability toward lanthanoid ions (Ln³⁺); the performance follows the order 7 ₄  ≈ 7 ₃  > 7 ₂ . Moderate extraction selectivity is observed for the extraction of Pr³⁺, Gd³⁺, and Yb³⁺ with 7 ₂ . X-ray crystallographic analysis of cluster [Tb₄L₄(H₂O)₆](Et₃NH)₄, which was prepared from 7 ₄ (H₄L) and Tb(NO₃)₃·6H₂O in the presence of Et₃N, reveals that no sulfonyl oxygens coordinate to the metal centers. This indicates that the high extractability of 7 ₄ originates from the electron-withdrawing nature of the sulfonyl function, which increases the acidity of two adjacent carboxy groups.     

Design and synthesis of ladder-shaped tetracyclic, heptacyclic, and decacyclic ethers and evaluation of the interaction with transmembrane proteins

Ladder-shaped polyether (LSP) toxins represented by brevetoxins and ciguatoxins are thought to bind to transmembrane (TM) proteins. To elucidate the interactions of LSPs with TM proteins, we have synthesized artificial ladder-shaped polyethers (ALPs) containing 6/7/6/6 tetracyclic, 6/7/6/6/7/6/6 heptacyclic, and 6/7/6/6/7/6/6/7/6/6 decacyclic systems, based on the convergent method via alpha-cyano ethers. The ALPs possessing the simple iterative structure with different numbers of rings would be useful for structure-activity relationship studies on the molecular length, which is supposed to be important when naturally occurring LSPs elicit their toxicity. Two series of ALPs were prepared to evaluate the hydrophilic or hydrophobic effects of the side chains: (i) both sides were functionalized as diols (A series), and (ii) one side remained as diol and the other side was protected as benzyl ethers (B series). To examine the interaction of these ALPs with TM proteins, dissociation of glycophorin A (GpA) dimers into monomers was evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The heptacyclic ether (ALP7B) elicited the most potent activity in the presence of 2% SDS buffer, whereas the decacyclic ether (ALP10A) exhibited an intriguing phenomenon to induce precipitation of GpA in a dose-dependent manner, under the low concentration of SDS (0.03%). ALP10A also induced precipitation of integrin alpha 1beta 1, a TM protein known to form heterodimers in the lipid bilayer membranes. The different activities among the ALPs can be accounted for by the concept of "hydrophobic matching" that is, lengths of the hydrophobic region including the side chains of ALP7B and ALP10A are ca. 25 A, which match the lengths of the hydrophobic region of alpha-helical TM proteins, as well as the hydrophobic thickness of lipid bilayer membranes. The concept of the hydrophobic matching would be a clue to understanding the interaction between LSPs and TM proteins, and also a guiding principle to design ALPs possessing potent affinities with TM proteins.     

Synthesis and properties of poly(ester urethanes) based on cellulose triacetate

Segmented poly(ester urethanes) were synthesized from oligomeric cellulose triacetate diols, poly(caprolactone)diols, and 1,6-hexamethylene diisocyanate. The effects of the molecular mass and structure of soft and hard segments of poly(ester urethanes) on their thermal behavior, mechanical properties, and degradation in aqueous solutions of a phosphate buffer were studied by DSC and IR spectroscopy. The combination of soft segments derived from poly(caprolactone)diols with M = (1.0–3.5) × 10³, hard segments based on depolymerized cellulose triacetate with M = (2–4) × 10³, and 1,6-hexamethylene diisocyanate makes it possible to synthesize poly(ester urethanes) with excellent mechanical characteristics. The degree of crystallinity of these polymers increases with a decrease in the molecular mass of the depolymerized cellulose triacetate block in the hard segment. As the soft segment lengthens, phase separation between domains of soft and hard segments becomes more pronounced. Upon incorporation of poly(ethylene glycol) blocks into the soft segments of poly(ester urethanes), their hydrophobicity is enhanced and biodegradability is accelerated.     

Design,synthesis, and biological evaluation of new ALDH2 activators

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is an important enzyme response for the metabolism or detoxification of toxic aldehydes, in particular acetaldehyde and 4-hydroxynonenal (4-HNE), which were important risk factors for acute alcoholism and stroke respectively. A special variant ALDH212 with reduced enzymatic activity was carried by a high percentage of East Asians, especially Han Chinese, and that could increase the risk of these diseases further. Therefore, ALDH2 activators had important potential clinical values. N-benzylbenzamide compounds represented by Alda-1 were the only ALDH2-specific activators that have been reported so far. In this study, three new classes of compounds were modified from Alda-1 to improve their water-solubility and then drug-like properties. The results showed that all compounds had increased water solubility and two classes of compounds exhibited good activation activity. Among them, compound I-6 showed the best activity.     

Design,synthesis and evaluation of spermine-based pH-sensitive amphiphilic gene delivery systems: Multifunctional non-viral gene carriers

Design and development of efficient non-viral gene delivery systems is critical to overcome various barriers for effective intracellular gene delivery.Eight new spermine-based protonatable surfactants were designed,synthesized and evaluated as non-viral pH-sensitive gene carriers.These carriers formed stable complexes with plasmid DNA at an N/P ratio as low as 2.The sizes of the carrier/pDNA nanoparticles (N/P = 12) were in the range of 90–130 nm,smaller than that of Lipofectamine2000/pDNA nanoparticles.The...     

Gas-phase oxidation reactions of Ta2+: synthesis and properties of TaO(2+) and TaO2(2+)

Gas-phase reactions of Ta(2+) and TaO(2+) with oxidants, including thermodynamically facile O-atom donor N(2)O and ineffective donor CO, as well as intermediate donors C(2)H(4)O (ethylene oxide), H(2)O, O(2), CO(2), NO, and CH(2)O, were studied by Fourier transform ion cyclotron resonance mass spectrometry. All oxidants reacted with Ta(2+) by electron transfer yielding Ta(+), in accord with the high second ionization energy of Ta (ca. 16 eV). TaO(2+) was also produced with N(2)O, H(2)O, O(2), and CO(2), oxidants with ionization energies above 12 eV; CO reacted only by electron transfer. The following charge separation products were also observed: TaN(+) and TaO(+) with N(2)O; and TaO(+) with O(2), CO(2), and CH(2)O. TaOH(2+), formed with H(2)O, reacted with a second H(2)O by proton transfer. TaO(2+) abstracted an electron from N(2)O, H(2)O, O(2), CO(2), and CO. Oxidation of TaO(2+) by N(2)O was also observed to produce TaO(2)(2+); on the basis of density functional theory (DFT) results, this species is a dioxide, {O-Ta-O}(2+). TaO(2)(2+) reacted by electron transfer with N(2)O, CO(2), and CO to give TaO(2)(+). Additionally, it was found that TaO(2)(2+) oxidizes CO to CO(2) and that it acts as a catalyst in the oxidation of CO by N(2)O. TaO(2)(2+) also activates H(2) to form TaO(2)H(2+). On the basis of the rates of electron transfer from N(2)O, CO(2), and CO to Ta(2+), TaO(2+), and TaO(2)(2+), the following estimates were made for the second ionization energies of Ta, TaO, and TaO(2): IE[Ta(+)] = 15.8 ± 0.3 eV, IE[TaO(+)] = 16.0 ± 0.5 eV, and IE[TaO(2)(+)] = 16.9 ± 0.4 eV. These IEs, together with recently reported bond dissociation energies, D[Ta(+)-O] and D[OTa(+)-O], result in the following bond energies: D[Ta(2+)-O] = 657 ± 58 kJ mol(-1) and D[OTa(2+)-O] = 500 ± 63 kJ mol(-1), the first of which is in good agreement with the value obtained by DFT.     

Design,synthesis, and biological evaluation of indolylidinepyrazolones as potential anti-bacterial agents

A series of indolylidinepyrazolones were synthesized using a simple, green, and effective route and evaluated as anti-bacterial agents. The compounds were further studied via structure-guided docking study. One of the compounds exhibiting H-bonding interactions with conserved residue Arg144 turned out to be the most potent compound of the series. The minimum inhibitory concentration values ranged from 50 to 25 μg/mL against Staphylococcus aureus in their anti microbial evaluation.     

Chemical transformations in the chains of cellulose dialdehydes and cellulose ethers

Nucleophilic exchange reactions of cellulose dialdehydes and ethers with a series of nucleophilic reagents have been investigated and the structural features of the reaction products have been established.Institute of the Chemistry and Physics of Polymers, Academy of Sciences of the Republic of Uzbekistan, fax (3712) 44 26 61. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 212–217, March–April, 1998.     

4(2)-Methoxyphenyl glycerol ethers in the synthesis of nonracemic di-O,O-acylglycerols

Effective methods for the synthesis of nonracemic 4- and 2-methoxyphenyl glycerol ethers from nonracemic 3-chloropropanediols and by direct resolution of the racemate, respectively, were developed. Some existing discrepancies related to the to chiroptical properties of their derivatives were eliminated. Both ethers were used to synthesize nonracemic 3-O-aryloxy-1,2-di-O′,O″-palmitoyl glycerols.