The first synthesis of ent-agelasine F

Agelasine F has previously been isolated from marine sponges (Agelas sp.) and has been associated with various bioactivities including inhibitory activity on Mycobacterium tuberculosis. No total synthesis of this natural product has been reported. ent-Agelasine F has now been synthesized for the first time, starting from (R)-pulegone. The synthesis is considerably more efficient than a previously reported route to rac-agelasine F. ent-Agelasine F is found to exhibit antimicrobial activity.     

Chemoenzymatic synthesis of calcilytic agent NPS-2143 employing a lipase-mediated resolution protocol

The kinetic resolution of chlorohydrin (±)-6 has been successfully carried out via a lipase-mediated transesterification with vinyl acetate in organic as well as ionic liquid media to yield (R)-alcohol 6 and (S)-acetate 7 in high enantioselectivity. An enantioconvergent synthesis has also been achieved by a Mitsunobu esterification of a mixture of (R)-alcohol 6 and (S)-acetate 7 in one pot to convert the (R)-alcohol 6 to (S)-acetate 7. (S)-Acetate 7 has been hydrolyzed by LiOH·H₂O to give epoxide (R)-2. This enantiopure epoxide has been used as a chiral precursor for the synthesis of calcilytic agent NPS-2143.     

Conductivity behaviour of proton conducting polymer gel electrolytes with PVdF-HFP

Electrical conductivity of polymer gel electrolytes containing different hydroxy substituted benzoic acids and polyvinylidenefluoride-hexafluoropropylene (PVdF-HFP) has been studied. The conductivity of solution and gel electrolytes shows ortho effect and has been found to depend upon the acidity constant of the acid used and varies as σ (ortho-) > σ (meta-) > σ (para-). The addition of PVdF-HFP to solution electrolytes results in an increase in conductivity and the conductivity of gel electrolytes has been found to be higher than that of the corresponding liquid electrolytes for all the three acids studied i.e. σ (gel) >σ (liquid). The increase in conductivity with polymer addition has also been found to depend upon the acid concentration.     

Diferric oxo-bridged complexes of a polydentate aminopyridyl ligand: synthesis,structure and catalytic reactivity

The catalytic reactivity of a group of diferric oxo-bridged complexes (1–3) of a tetradentate ligand (bpmen = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-1,2-diaminoethane) toward alkane hydroxylation has been evaluated. Among the three complexes, the µ-oxo diiron(III) complex [Fe(bpmen)(µ-O)FeCl₃] (1) has been synthesized for the first time. The complex 1 has been characterized by spectroscopic analysis and X-ray crystallography. At room temperature, the µ-oxo diiron(III) complexes 1–3 have been found to be useful catalysts in hydroxylation of alkanes with m-chloroperbenzoic acid as oxidant. [Fe(bpmen)(µ-O)FeCl₃] (1) has been found to be the most active catalyst. Moreover, the catalytic ability of the complexes in the oxidation of alcohols to ketones with hydrogen peroxide at room temperature has also been investigated.     

Cinetique de polymerisation du styrene en presence de peroxyde de benzoyle p,p′ bis-bromomethyle synthese de polymeres peroxydes

The free radical polymerization of styrene has been studied by using p,p′-bisbromomethyl benzoyl peroxide as initiator containing a chain transfer group. The rate constant of decomposition (k_d) of this peroxide has been determined at various temperatures, as well as the efficiency factor f and the transfer constant to initiator C₁. At 60°, f = 0·70 ± 0·05 and C₁ = 0·5. Polystyrene containing peroxide groups has been prepared by using this initiator. The highest yield in polymeric peroxide has been obtained for polymerization in emulsion at 40°.     

The studies of molecular structure of Poly(1-trimethylsilyl-1-propyne) stereoisomers by the flow birefringence method

Optical properties of poly-1-trimethylsilyl-1-propyne (PTMSP) stereoisomers in solutions have been studied by means of flow birefringence method. Stereoisomers were chosen with various trans- and cis-configurations abundances of double CC bonds in monomeric units. The differences of main polarizabilities (α₁ − α₂) or statistical segments have been determined. Significant growth of (α₁ − α₂) values with increasing of the trans-isomer contents in chain molecule has been found. Optical anisotropy of monomeric segments, having cis- and trans-configurations, has been theoretically evaluated. It has been shown that observed significant increase of experimentally measured (α₁ − α₂) values cannot be sufficiently explained by only specific chain polarizability growth due to higher trans-isomers contents. It has been demonstrated that high (α₁ − α₂) value and it’s growth with increase of abundance of monomeric segments in trans-configuration has been caused by thermodynamical rigidity increase, i.e., higher number of monomeric units included into PTMSP statistical segment.     

Prediction of permselectivity of nitrate and acetate ions in the electrodialysis of aqueous solutions

Electrodialysis of aqueous solutions of acetic and nitric acids encountered in the industrial practice of deacidification of raw glyoxal solutions has been carried out to investigate the permselectivity of the system. The dependence of the permselectivity coefficient τ on experimental parameters such as flow velocity (V), current density (I), concentration of anions (C_i), etc. has been evaluated. A correlation between τ and the critical parameters has been obtained. Well-known theoretical equations have been used to calculate τ at limiting current density I_lim and as I approaches zero. Calculated results are compared with observed values. Limitations of theoretical procedures when applied to a system containing a weak acid are explained.     

Synthetic approach toward cis-disubstituted γ- and δ-lactones through enantioselective dialkylzinc addition to aldehydes: application to the synthesis of optically active flavors and fragrances

A versatile and straightforward approach to optically active cis-4,5-disubstituted γ- and δ-lactones by catalytic enantioselective addition of dialkyzincs to cinnamic aldehydes and RCM ring closure has been reported. The synthetic importance of the enantioselective dialkylzinc alkylation of aldehydes has been thus widened. Such an approach has then been employed for the enantioselective synthesis of naturally occurring γ-lactone flavors like (S)-5-ethyl-butanolide (6a) and (4S,5S)-cis-whisky lactone (6b) and extended to the preparation of δ-lactones like (5S,6S)-5-methyl-6-ethylpentanolide (9a), precursor of the pheromone serricornin.     

Synthesis and transport studies of new enantiopure lipophilic crown ethers containing a diarylphosphinic acid unit

The synthesis of new enantiopure lipophilic crown ethers (S,S)-6, (R,R)-6 and (S,S)-7 containing a diarylphosphinic acid unit has been carried out. The transport ability of these ligands has been studied in an aqueous source phase/lipophilic organic bulk liquid membrane/aqueous receiving phase system controlled by the pH of the media. The transport of metal ions and amines has also been studied. These studies showed high selectivity for protonated amines.     

Cobalt(II) complexation with immobilized proteinases of Candida albicans

Complexation of cobalt(II) ion with proteolytic enzymes of Candida albicans (SAP C.alb.) of induced (ISAP C.alb.) and constitutive (CSAP C.alb.) types immobilized on the cellulose nitrate membrane surface has been studied. The maximal sorption capacity of cellulose nitrate membranes with covalently immobilized induced proteinase ISAP C.alb. with respect to Co(II) ions is 16.5 ??mol/cm², and that for CSAP C.alb. is 27.7 ??mol/cm². The model of fixed polydentate centers has been used for describing complex formation. The complexation constants (?? _n ) and the average number of immobilized ligands coordinated to one metal atom (n) have been determined. The specificity of binding of immobilized enzyme molecules to Co(II) ion has been assessed.     

Ion-selective and complexation properties, vibrational spectra, and crystal and molecular structure of 1,5-bis[2-(hydroxyethoxyphosphoryl)phenoxy]-3-oxapentane

The ion-selective properties of 1,5-bis[2-(hydroxyethoxyphosphoryl)phenoxy]-3-oxapentane H₂R² have been described. The molecular and crystal structure of H₂R² has been determined by powder X-ray crystallography and IR spectroscopy. The molecule has the twofold symmetry axis, orthorhombic crystal system, space group Pbcn, a = 16.830(2) ?, b = 8.866(15) ?, c = 15.7190(2) ?, V = 2346.1(6) ?³, Z = 4. A new CuR² · 2H₂O complex has been synthesized and characterized.     

Influence of chemical composition of electrode material on the differential capacitance characteristics of the ionic liquid | electrode interface

The electrical double layer structure at polycrystalline metal | ionic liquid interface has been studied using cyclic voltammetry, electrochemical impedance spectroscopy and in situ infrared methods. Polycrystalline Bi(PC), Pb(PC), Au(PC) and Pt(PC) electrodes have been prepared using ultra-high vacuum magnetron sputtering method. Noticeable dependence of differential capacitance on the electrode potential has been observed. For all electrodes, a wide well-expressed minimum in capacitance, potential (C, E) curve has been shown. For graphene, C(0001), carbide-derived carbon and Bi(PC) U-shaped curves and for Pb(PC), Au(PC) and Pt(PC) M-shaped C, E curves have been measured. Dependence of the C, E curve shape on the electrode chemical composition has been explained by the different position of the image plane of surface charge, dependent on the electronic characteristics of the electrodes under study.     

Molecular-dynamics simulation of the structural stability,energetics, and melting of Cu n(n = 13–135) clusters

Cluster properties of copper have been investigated using the Molecular-Dynamics md technique. The structural stability and energetics of spherical Cu_n (n = 13–135) clusters have been investigated at temperatures T = 1 K and T = 300 K. It has been found that the average interaction energy per atom in the cluster decreases and reaches an asymptotic value as cluster size increases. The melting behaviour of clusters n = 13 and n = 55 have been investigated. It has been found that the melting temperature decreases as cluster size increases, and for clusters with multishell structures melting starts from the outermost shell. In the simulation an emprical potential energy function (PEF) proposed by Erkoç has been used, which contains two-body atomic interactions.     

Synthesis of the antiepileptic (R)-Stiripentol by a combination of lipase catalyzed resolution and alkene metathesis

The enantiopure (ee >99%) antiepileptic (R)-(+)-Stiripentol has been stereoselectively synthesized via cross metathesis of 5-vinylbenzo[d][1,3]dioxole 1 and (R)-(+)-4,4-dimethylpent-1-en-3-ol (R)-(+)-2. A novel one-pot two-step pathway for the synthesis of 5-vinylbenzo[d][1,3]dioxole 1 starting from 3,4-dihydroxycinnamic acid has been introduced. A lipase catalyzed kinetic resolution access to enantiopure (R)-(+)-4,4-dimethylpent-1-en-3-ol (R)-(+)-2 (ee >99%) has also been developed.     

Crystal structure of uranyl tungstate Cs2U2WO10

A representative of uranyl tungstates Cs₂U₂WO₁₀ has been synthesized. A single crystal X-ray diffraction experiment has been performed for the compound prepared and its crystal structure has been solved. It is monoclinic, space group P2₁/n, a = 8.4611(5) Å, b = 28.691(2) Å, c = 9.6499(6) Å; β = 107.073(1)°, R ₁ = 0.086 for 4599 independent reflections with I > 2σ(I). The crystalline structure of the compound is formed by infinite negatively charged layers [U₂WO₁₀] _2∞ ^δ? interleaved with cesium cations which bond the layers. The compound has been studied with IR spectroscopy, and absorption bands of its spectrum have been assigned.     

The nπ* states of the thiocarbonyl halides: The ā3A ← X̄1A' electronic transition in thiocarbonyl chlorofluoride

The visible absorption spectrum of thiocarbonyl chlorofluoride, C1FCS in the 495-nm region has been observed in the vapour phase under conditions of high resolution and pressure x path-length and has been assigned to the ā³A'' (n, π^*) ← X?¹A' electronic transition. Three of the six fundamental modes have been assigned for the upper electronic state. Prom a fit of the observed levels in v¹_o (the out-of-plane wagging mode) to the eigenvalues obtained from a quadratic-gaussian potential, the barrier to inversion in the ā³A state has been evaluated to be 1622 cm^?1 The electronic effects of replacing a sulphur by an oxygen atom on the height of the barrier to inversion in the nπ^* carbonyl and thiocarbonyl halides have been explored by the CNDO/2 method. The much lower barriers in the thiocarbonyl compounds has been attributed to the sulphur d_xz AO which is not present in the carbonyl compounds. This AO, which has relatively high weight in the LCAOs which form the π^* MO, has the effect of relieving some of the antibonding density which resides on the carbon atom and thereby reduces the barrier to inversion.     

Structural and electrical conductivity studies of Li x AlZr[PO4]3 (x = 1.8, 2.0, 2.2), solid electrolyte for lithium-rechargeable batteries

In the present study, Li _x AlZr[PO₄]₃ (x = 1.8, 2.0, 2.2) has been prepared by the Pechini-type polymerizable precursor method, and structural and electrical analyses have been performed. Formation of the compound has been confirmed from X-ray diffraction pattern. Vibrational analysis has been performed using Fourier transform infrared spectroscopy. Ion transport mechanism has been analyzed using the AC impedance technique. Electrical characterization reveals that the maximum conductivity (4.4 × 10^?5S cm^?1) has been observed for the sample Li_2.2AlZr[PO₄]₃ at 673K.     

2,2′-Dihydroxy-3,3′-dimethoxy-5,5′-dimethyl-6,6′-dibromo-1,1′-biphenyl: preparation,resolution, structure and biological activity

The preparation and resolution of the titled conformationally stable biphenyl 1 has been performed in high chemical yield starting from creosol 2. Enantiopure biphenyls (aR)-(+)-1 and (aS)-(−)-1 were obtained by the corresponding menthylcarbonate diastereomer and successive reduction. The absolute configuration and specific rotation were correlated by X-ray analysis of the crystal structure of diastereopure menthylcarbonate (aS,1R,1′R,2S,2′S,5R,5′R)-(+)-16. Preliminary biological evaluation of both racemic enantiomers of 1 has been carried out on melanoma cell lines and significant and selective anticancer activity has been observed for the enantiomer (aS)-(−)-1.     

Crystal structure of the Fe6−xGayGe5−y (x ∼0.5, y = 1.3) ternary compound

The single crystal of Fe_6−xGa_yGe_5−y (x ∼0.5, y = 1.3(1)) has been obtained from arc-melting of the elements and its crystal structure has been investigated by single-crystal X-ray diffraction analysis. The compound crystallizes in the hexagonal space group P6₃/mmc (No. 194) with a = 8.0346(2) Å, c = 5.007(1) Å, Z = 1 and adopts the Ti₆Sn₅ structure type with a refined composition of Fe_5.52(12)(Ga/Ge)₅. By a mean of scanning electron microscopy the composition of the single crystal has been determined as Fe_4.9(2)Ga_1.3(1)Ge_3.7(1). The crystal structures of the Fe_6−xGa_yGe_5−y (x ∼0.5, y = 1.3(1)) and all compounds in the Fe–Ge binary system have been crystallographically analyzed and structural relationship has been established.     

Enhanced general analytical equation for the kinetics of the thermal degradation of poly(lactic acid) driven by random scission

An enhanced general analytical equation has been developed in order to evaluate the kinetic parameters of the thermal degradation of poly(lactic acid) (PLA) at various linear heating rates and at constant rate conditions. This improvement consisted of replacing the n-order conversion function by a modified form of the Sestak-Berggren equation f(α) = c(1?α)ⁿα^m, which led to better adjustment of experimental data, and also adequately represented the conventional mechanisms for solid-state processes. The kinetic parameters so obtained have been compared to those determined by conventional differential and isoconversional methods. Given that the thermal degradation of PLA has been argued to be caused by random chain scission reactions of ester groups, the conversion function (α) = 2(α^1/2?α), corresponding to a random scission mechanism, has been tested.