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Breast cancer is a worldwide commonly found malignancy in women and effective treatment is regarded as a huge clinical challenge even in the presence of several treatment options. Extensive literature is available demonstrating polyphenols as phytopharmaceutical anticancer agents. Among the polyphenols, quercetin and curcumin have been reported to have a strong potential against breast cancer. However, so far, no comprehensive study has been performed to demonstrate the anticarcinogenic effects of curcumin, quercetin, and their combinations with somatostatin on the fatty acid profile of breast cancer cell membranes. We used MCF-7 and MDA-MB231 breast cancer cells incubated with curcumin and quercetin for 24 h, in the absence and presence of somatostatin, at their [EC.sub.50] concentrations to evaluate membrane fatty acid based functional lipidomics together with the followup of EGFR and MAPK signaling pathways. The two cell lines gave different membrane free fatty acid reorganization. In MCF-7 cells, the following changes were observed: an increase of [omega]6 linoleic acid in the cells incubated with somatostatin + quercetin and quercetin and a decrease of [omega]3 acids in the cells incubated with somatostatin + curcumin compared to somatostatin and significant increases of monounsaturated fatty acid (MUFA), mono-trans arachidonic acid levels and docosapentaenoic acid for the cells incubated with somatostatin + quercetin compared to the control cells. In MDA-MB231 cells, incubations with curcumin, quercetin, and somatostatin + quercetin induced the most significant membrane remodeling with the increase of stearic acid, diminution of [omega]6 linoleic, arachidonic acids, and [omega]3 (docosapentaenoic and docosahexaenoic acids). Distinct signaling pathway changes were found for these cell lines. In MCF-7 cells, separate or combined incubations with somatostatin and quercetin, significantly decreased EGFR and incubation with curcumin decreased MAPK signaling. In MDA-MB231 cells, incubation with curcumin decreased AKT1 and p-AKT1 (Thr308) levels. Incubation with curcumin and quercetin decreased the EGFR levels. Our results showed that cytostatic and antioxidant treatments can be combined to induce membrane fatty acid changes, including lipid isomerization as specific free radical driven process, and to influence signaling pathways. This study aimed to contribute to the literature on these antioxidants in the treatment of breast cancer to clarify the effects and mechanisms in combination with somatostatin. Key words: somatostatin, curcumin, quercetin, breast cancer, cell signaling, membrane fatty acid profile. Le cancer du sein est une maladie frequente chez les femmes a l'echelle mondiale et son traitement efficace est considere comme etant un immense probleme clinique, meme en presence de plusieurs options therapeutiques. Il existe une grande quantite de donnees publiees decrivant les polyphenols comme etant des agents phytopharmaceutiques anticancereux. Parmi les polyphenols, on a rapporte que la quercetine et la curcumine sont potentiellement fort utiles contre le cancer du sein. Cependant, jusqu'a maintenant, aucune etude exhaustive n'a tente de montrer les effets anticancerigenes de la curcumine, de la quercetine et de leur association avec la somatostatine sur le profil des acides gras membranaires des cellules de cancer du sein. A l'aide de cellules de cancer du sein MCF-7 et MDA-MB231 incubees avec de la curcumine et de la quercetine pendant 24 h, en absence ou en presence de somatostatine et a leur concentration efficace mediane, nous avons evalue la lipidomique fonctionnelle basee sur les acides gras membranaires ainsi que suivi les voies de signalisation des recepteurs du facteur de croissance epidermique (EGF pour << epidermal growth factor >>) et de la MAP kinase. Les deux lignees cellulaires ont donne differentes reorganisations des acides gras libres. Dans les cellules MCF-7, nous avons observe les modifications suivantes : hausse de l'acide linoleique [omega]6 avec l'association somatostatine + quercetine et la quercetine, et abaissement des acides gras [omega]3 plus marque dans les cellules incubees avec l'association somatostatine + quercetine qu'avec la somatostatine, ainsi qu'une augmentation notable plus importante des taux d'acides gras mono-insatures, d'acide arachidonique mono-trans et d'acide docosapentaenoique pour les cellules incubees avec l'association somatostatine + quercetine que chez les cellules temoins. Pour les cellules MDA-MB231, l'incubation avec de la curcumine, de la quercetine et l'association somatostatine + quercetine a entraine le plus important remodelage membranaire avec une hausse de l'acide stearique, un abaissement des acides gras linoleique [omega]6, arachidonique et [omega]3 (acides docosapentaenoique et docosahexaenoique). Nous avons observe des modifications distinctes des voies de signalisation pour ces lignees cellulaires. Pour les cellules MCF-7, l'incubation avec de la somatostatine ou de la quercetine separement ou en association entrainait une inhibition marquee de la voie de signalisation des recepteurs de l'EGF, et l'incubation avec de la curcumine entrainait une inhibition de la voie de signalisation de la MAP kinase. L'incubation des cellules MDA-MB231 avec de la curcumine a entraine une diminution des taux d'AKTl et de p-AKT1 (Thr308). L'incubation avec de la curcumine et de la quercetine entrainait une diminution des taux des recepteurs de l'EGF. Nos resultats ont montre que des traitements cytostatiques et antioxydants peuvent etre associes pour produire des changements dans les acides gras membranaires, y compris une isomerisation lipidique en tant que processus specifique entraine par les radicaux libres, ainsi que pour influencer les voies de signalisation. Cette etude visait a ajouter aux connaissances publiees quant a l'utilisation de ces antioxydants dans le traitement du cancer du sein, en vue d'en clarifier les effets et les modes d'action en association avec la somatostatine. [Traduit par la Redaction] Mots-cles: somatostatine, curcumine, quercetine, cancer du sein, signalisation cellulaire, profil des acides gras membranaires., Introduction Cancer is a deadly global disease and a critical barrier in the cumulative life span of the affected population (Bray et al. 2018). On the basis of the recorded [...]

Introduction Knowing the degree of unsaturation and relative amounts of cis and trans isomerization in edible oils and fats is important in today's food industry. This is necessary for both [...]

Several calculations are carried out to analyze the mechanism of the novel intramolecular silyl transfer reaction in the heterodimetallic chemistry. The study shows that the transition states of migration and isomerization in the reaction can be easily done at room temperature, hence making the reaction simple.

The different modes of cascade cycloisomerizations of alkynyl ketones and cyclic imines proceeding through different types of migration of acyloxy, phosphatyloxy and tosyloxy groups are developed in order give multisubstituted furans and indolizines in good to high yields. These methods have allowed the efficient synthesis of tri- and tetrasubstituted furans and N-fused heterocycles.

One-electron reduction of methanesulfonyl chloride in the presence or in the absence of oxygen and the ability of MeS[O.sub.2.sup..] radical to act as oxidant and as catalyst in the cis-trans isomerization of unsaturated fatty acids is described. Unambiguous evidence is provided for a long-lived electron adduct to sulfonyl chlorides, which has acted as reductant and has established equilibrium with [O.sub.2.sup..-].

The proline effect in model dipeptides Pro-Gly and Gly-Pro is studied. Kinetic analysis of the Gly-Pro radical system has shown that ring-openings can be triggered by radical sites at both sides of the proline residue in larger peptides and the isomerizations within the proline residue has described the proline effect in electron capture and transfer dissociation.

Electron spin resonance (ESR) and electron spectroscopies were used to study the structures and cis-to-trans photoisomerization of hexafluoro-1,3-butadiene radical cation. The results reveal that the relative abundance of s-cis-HFBD to s-trans-HFBD was 4.0 immediately after being formed by [gamma]-irradiation and most s-cis-HFBD was isomerized to s-trans-HFBD by visible light illumination.

The synthesis of the C4-C24 fragment of the macrolactin A is presented. The synthetic approach includes two isomerizations to specifically develop the (8E,10Z) and (16E,18E) dienes by a sequential Claisen rearrangement/allene isomerization and a [Ph.sub.3]P-catalyzed isomerization of an yne-one, respectively.

A study was conducted to show that the relative populations of two rotamers in the hydrazone of 2H-perfluoro-2-methyl-3-pentanone could be altered from one extreme to the other by increasing the Lewis basicity of the solvent. The rate of E/Z interconversion is found to be insensitive to the choice of solvent and it is consistent with the conclusion that the isomerization occurs via N-inversion and not C=N bond rotation.

A study explores the N/[eta.sup.2] equilibrium for TpW(NO)-(P[Me.sub.3])(pyridine) and its dependence on the heterocycle substituents and metal oxidation state. It is found that the ability of tungsten to bind pyridines in an [eta.sup.2] manner is dependent on both the electronic and steric properties of the substituents as well as the oxidation state of the metal.

The mechanisms of the photochemical isomerization reactions are investigated by using a model of 2-cyanopyrrole and 2-cyano-5-methylpyrrole with CASSCF and MP2-CAS methods and the 6-31 1(d,p) basis set. The analysis has shown that the conical intersections play a crucial role in the photoisomerization reactions of cyanopyrroles.

In haloarchaea, light-driven ion transporters have been modified by evolution to produce sensory receptors that relay light signals to transducer proteins controlling motility behavior. The proton pump bacteriorhodopsin and the phototaxis receptor sensory rhodopsin II (SRII) differ by 74% of their residues, with nearly all conserved residues within the photoreactive retinal-binding pocket in the membrane-embedded center of the proteins. Here, we show that three residues in bacteriorhodopsin replaced by the corresponding residues in SRII enable bacteriorhodopsin to efficiently relay the retinal photoisomerization signal to the SRII integral membrane transducer (Htrll) and induce robust phototaxis responses. A single replacement (Ala-215-Thr), bridging the retinal and the membrane-embedded surface, confers weak phototaxis signaling activity, and the additional two (surface substitutions Pro-200-Thr and Val-210-Tyr), expected to align bacteriorhodopsin and Htrll in similar juxtaposition as SRII and Htrll, greatly enhance the signaling. In SRII, the three residues form a chain of hydrogen bonds from the retinal's photoisomerized [C.sub.13] = [C.sub.14] double bond to residues in the membrane-embedded [alpha]-helices of Htrll. The results suggest a chemical mechanism for signaling that entails initial storage of energy of photoisomerization in SRII's hydrogen bond between Tyr-174, which is in contact with the retinal, and Thr-204, which borders residues on the SRII surface in contact with Htrll, followed by transfer of this chemical energy to drive structural transitions in the transducer helices. The results demonstrate that evolution accomplished an elegant but simple conversion: The essential differences between transport and signaling proteins in the rhodopsin family are far less than previously imagined. bacteriorhodopsin | phototaxis | retinal | sensory rhodopsin | transport

The bridge-to-chelate isomerization of the dppe ligand in the [H.sub.4][Ru.sub.4][(CO).sub.10](dppe) was kinetically investigated by UV-vis and NMR spectroscopies. The dppe ligand isomerization was found to be reversible in favor of the chelating isomer and on the basis of calculated activation parameters, a nondissociative rearrangement of the dppe ligand involving a bridging phosphine moiety is proposed.

The nematic and twisted nematic liquid crystals mixed with azobenzene (AB), spirooxazine (SO) and spiropyran (SP) are investigated by using spectroscopic methods, including birefringence and polarized transmission, to monitor the amplitude of the changes upon phototransformation as well as the dark kinetics. The results have shown SP to be an interesting photochemical probe as it has orientation photochromism and is able to adequately sense the orientation dependent polarity of this anisotropic medium.

The structures and vibrational frequencies of [UO2(H2O).sup.2+] and [UO2(H2O)5.sup.2+] is calculated using density functional theory and are in reasonable agreement with experiment. Calculation of the free energy of solvation of the uranyl cation yielded an upper bound to the solvation energy of -410 plusmn 5 kcal/mol, consistent with the best experimental value of -421 plusmn 15 kcal/mol.

The properties of N-methylacetamide along a cis-trans isomerization pathway reported by twisting about the C(O)-N bond are investigated at finite temperature both in vacuo and in explicit water solvent. The electronic structure of the NMA molecule predicted by the ab initio method along the reaction coordinate is analyzed to understand the changes in peptide 'partial-double' bond character [C(O)-N] as isomerization takes place.

Density functional theory (DFT) is used to investigate the influence of rotational and geometrical isomerism on the nonlinear optical (NLO) properties, specifically the first-order hyperpolarizability [beta], of chromophores of current interest. The study of various types of isomerization has shown that the influence of electronic structure on the development of a large hyperpolarizability consists of many competing factors, making electronic structure calculations very valuable when designing the next generation of chromophores.

Mass spectrometry has become an essential tool in delineating the structural properties of a new series of amino acid functionalized acyclic diene metathesis (ADMET) polymers known as bioolefins. These measurements, coupled with the measurement of the polymers chemical and physical properties, assist in the determination of their utility as biomaterials. In the present study, a set of five polymers with different bulk size and electronic properties were chosen for structural analyses by MALDI-TOF, MALDI-FTICR, and DIOS-TOF. The obtained data show that due to the competing metathesis and isomerization during ADMET, depending on their structural properties, the olefins display different selectivity toward main metathesis or isomerized products.

The omega-3 polyunsaturated fatty acids (PUFA) like stearidonic acid (SDA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and its chain fragment models are studied and significant conformations are selected for the cis and trans isomers to obtain the thermodynamic functions for the cis-trans isomerization and for folding. The structural analysis has shown some significant differences in thermodynamic function of the trans- and cis-PUFAs.

The possible competition of Z/E versus hydrogen-shift isomerization in (E)-5-phenyl-3-penten-2-one (E-1) and (E)-5-phenyl-4-penten-2-one (E-2) is analyzed, both experimentally and theoretically. Density functional theory (DFT) calculations have confirmed that the free energy difference and computations of Boltzmann-weighted (super 1)H NMR spectra are useful in confirming the assignment of the isomers.

Aluminum chloride is used extensively as Lewis acid catalyst in a variety of industrial processes, including Friedel-Crafts and Ci/F exchange reactions. Experimental and computational methods is used to investigate the surface structure and catalytic propertied of solid AlCl3.

cis-Oligo(phenylenevinylene)s (OPVs) are synthesized by Suzuki-Miyaura coupling of arylboronic acids with (Z)-bromoalkenes in over 96% geometrical purity. Effect of PI-conjugation chain length on photoisomerization behavior of OPVs is described.

New examples of the tandem ring-closing metathesis (RCM)-isomerization reaction that allow for the efficient preparation of fluorinated as well as nonfluorinated, unsaturated lactam derivatives are developed. The process is efficient in the preparation of five- to eight-membered rings, in which the RCM step is very fast because of the favorable ring size formation and thus occurs well before the isomerization.

Two experimental methods inducing population transfer spectroscopy are introduced and applied to a series of prototypical isomerization reactions. The method gives up full state-to-state selection under collision-free conditions, to study larger flexible molecules and molecular clusters with complicated multidimensional potential energy surfaces.

Conjugated linoleic acids (CLAs) affect body fat gain, carcinogenesis, insulin resistance, and lipid peroxidation in mammals. Several isomers of CLA exist, of which the (9Z, 11E) and (10E, 12Z) isomers have beneficial effects on human metabolism but are scarce in foods. Bacterial polyunsaturated fatty acid isomerases are promising biotechnological catalysts for CLA production. We describe six crystal structures of the Propionibacterium acnes polyunsaturated fatty acid isomerase PAl in apo- and product-bound forms. The three-domain flavoprotein has previously undescribed folds outside the FAD-binding site. Conformational changes in a hydrophobic channel toward the active site reveal a unique gating mechanism for substrate specificity. The geometry of the substratebinding site explains the length preferences for C18 fatty acids. A catalytic mechanism for double-bond isomerization is formulated that may be altered to change substrate specificity for syntheses of rare CLAs from easily accessible precursors. conjugated linoleic acid | flavoprotein | polyenoic fatty acid isomerase | structure-based mechanism

A nonenzymatic posttranslational modification of proteins and peptides is the spontaneous deamidation of asparaginyl residues via a succinimide intermediate to form a varying mixture of aspartyl and isoaspartyl residues. The isoaspartyl residue is generally difficult to detect particularly using mass spectrometry because isoaspartic acid is isomeric with aspartic acid so that there is no mass difference. However, electron capture dissociation has demonstrated the ability to differentiate the two isoforms in synthetic peptides using unique diagnostic ions for each form; the [c.sup.[??].sub.r] + 58 and [z.sub.l-r] - 57 fragment ions for the isoAsp form and the Asp side chain loss [((M + nH).sup.(n-1)+[??]] - 60) for the Asp form. Shown here are three examples of isoaspartyl detection in peptides from proteins; a deamidated tryptic peptide of cytochrome c, a tryptic peptide from unfolded and deamidated ribonuclease A, and a tryptic peptide from calmodulin deamidated in its native state. In all cases, the [c.sup.[??].sub.r] + 58 and [z.sub.l-r] - 57 ions allowed the detection and localization of isoaspartyl residues to positions previously occupied by asparaginyl residues. The [(M + nH).sup.(n-1)+[??]-60 ions were also detected, indicating the presence of aspartyl residues. Observation of these diagnostic ions in peptides from proteins shows that the method is applicable to defining the isomerization state of deamidated proteins.

Double bond rotation and electrocyclic ring closure were used for examining the isomerization of (E,E)-1,3-cycloheptadiene. (E,Z)-1,3-cycloheptadiene with a barrier of 7.2 kcal mol(super -1) was observed in the first pathway whereas the trans isomer of bicyclo[3.2.0]hept-6-ene with a barrier of 13.0 kcal mol(super -1) was observed in the second pathway.

Fluorescence spectroscopy, powder X-ray diffraction, H NMR and HPLC were used for examining the cis-trans photoisomerization of crystalline or powdered cis, cis-1,4-diphenyl-1,3-butadiene (cc-DPB) at room temperature. In a crystal to crystal reaction, high conversions of up to 90 percent to the trans, trans isomer were observed.

A study of the fluorescent spectra of the green fluorescence protein (GFP) and the anionic form of p-hydroxybenzylidenemethylimidazolone (p-HBDI) reveals a well-resolved vibronic structure but broad and structureless chromophore spectra at lower temperatures. The results show that the cis-trans isomerization exhibited by the protein significantly narrows the fluorescence spectra, which is otherwise consistent with the decay of the torsional deformation (TD).

Fistulosin, which was isolated from the root of the Welsh onion, is a novel indole alkaloid that has antifungal activity. The first total synthesis of the reported structure of fistulosin using cycloisomerization of diene is described.

A study to determine the effects of the 4(R)-substitution on prolyl ring by electron-withdrawing group on the conformational preference and prolyl cis-trans isomerization in the gas phase, chloroform and water is conducted. The results reveal that the 4(R)-substitution by electron-withdrawing groups did not affect significant changes in backbone torsion angles as well as endocyclic torsion angle in the prolyl ring.

Adsorption of N(sub 2) was studied on zeolite H-Y (H-USY), ultrastabilized H-Y, H-mordenite, H-ZSM-5, H-beta, and on sulfated zirconia-titania (SZT) mixed oxide by diffuse reflectance infrared transform spectroscopy. The results revealed that the intrinsic acid strength of the solids followed the order of H-ZSM-5 approximately equal to H-mordenite approximately equal to H-beta > H-USY approximately equal to SZT approximately equal to ultrastabilized H-Y.

Amide-linked spiropyran-anthraquinone (SP-AQ) conjugates were mediated to ZnTPPS(super 4-) photosensitized transmembrane reduction of occluded Co(bpy)(sub 3)(super 3+) within unilamellar phosphatidylcholine vesicles by external EDTA. Examination revealed low quantum yields due to unproductive quenching of ZnTPPS(super 4-) by spiropyran (SP) and merocyanine (MC) groups on the dye and back-electron transfer between semiquinone and ZnTPPS(super 3-).

A method for the calculation of anharmonic vibrational energy levels for the bound generalized normal modes along a reaction path that is based on second order perturbation theory in curvilinear internal coordinates is presented. For HCN, HNC, and the saddle point of the HCN/HNC isomerization reaction on the potential energy surface, this method yield an average absolute error in the zero point energy and fundamentals of only 2 cm(super -1), compared to 63 cm(super -1) with the harmonic approximation.

The isomerically pure 10-iodo acid [closo-1-CB(sub 9)H(sub 8)-1-COOH-10-I](super -) was prepared in four steps from B(sub 10)H(sub 14) in about 10% overall yield. In the preparation the critical step that exhibiting the greatest variability is seperation of desired pure 10-iodo acid [closo-1-CB(sub 9)H(sub 8)-1-COOH-10-I](super -) from 6-iodo isomer 5 by recrystallization.

The synthesis of a variety of benzophosphepine complexes themselves serves as convenient phosphinidene precursors at elevated, substituent-dependent temperatures, by two successive hydrophosphinations of 1,2-diethynylbenzene. The accessibility of 3H-benzophosphepine complexes is demonstrated for a variety of metals and substituents under mild conditions in acceptable yields.

Study of the photodissociation dynamics of the ethoxy radical at energies from 5.17 to 5.96 eV using photofragment coincidence imaging is presented. It is concluded that the statistical dissociation on the ground-state surface does not occur for any of the observed product channels and that isomerization to CH(sub 2)CH(sub 2)OH prior to OH loss probably occurs on an excited-state surface.

The photoassisted reaction of O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) droplets in air is examined. Under ultraviolet (UV) light irradiation, it is possible for VX molecule in air to undergo isomerization of S-esters to O-esters, cleavage of P-S, S-C and C-N bonds and ozonation of tertiary amines.

The structures, energetic, spectroscopies, and isomerization of various doublet Si2CP species are explored theoretically. Implications in interstellar space and P-doped SiC vaporization processes are discussed.

Hydroxyglycine, the ammonia adduct of glyoxylic acid, was found to react with various allylboronates in the presence of triethylamine in methanol to give unprotected [alpha]-amino acids directly with high stereoselectivity. For instance, the reactions with (E)- and (Z)-crotylboronates afforded the corresponding anti- and syn-crotylated products (isoleucine and alloisoleucine after hydrogenation) with high diastereoselectivity, respectively. Interestingly, it was found that isomerization of the products ([gamma]-adducts to [alpha]-adducts) occurred under the reaction conditions in some cases. Control experiments have suggested that the isomerization took place via 2-aza (or azonia) Cope rearrangement of imines derived from [gamma]-adducts and glyoxylic acid. Key words: hydroxyglycine, glyoxylic acid, allylboronates, [alpha]-amino acids, allylglycines, isoleucine, alloisoleucine, stereoselective reactions, isomerization, 2-aza (azonia) Cope rearrangement. On a trouve que l'hydroxyglycine, le produit d'addition de l'ammoniac sur l'acide glyoxylique, reagit avec divers allylboronates, en presence de triethylamine dans le methanol, pour conduire directement a la formation d'acides [alpha]-amines non proteges, avec une stereoselectivite elevee. Par exemple, les reactions des (E)- et (Z)-crotylboronates conduisent respectivement aux produits anticrotyles et syncrotyles correspondants (isoleucine et alloisoleucine apres hydrogenation) avec des diastereoselectivites elevees. Fait interessant, on a trouve que, dans les conditions experimentales et pour quelques cas, il se produit une isomerisation des produits (adduits [gamma] en adduits [alpha]). Des experiences de controle ont suggere que l'isomerisation se produit par un rearrangement 2-aza (ou azonia) de Cope des imines derivees d'adduits [gamma] et de l'acide glyoxylique. Mots cles : hydroxyglycine, acide glyoxylique, allyboronates, acides [alpha]-amines, allylglycines, isoleucine, alloisoleucine, reactions stereoselectives, isomerisation, rearrangement 2-aza (ou azonia) de Cope. [Traduit par la Redaction]

Palladium(II) complexes of bis(phosphine)monooxide and bis(phosphine)monosulphide ligands with the general formula [[Ar.sub.2]P(C[H.sub.2]).sub.n]P(E)[Ar.sub.2] are described (n = 1 (dmapmE), E = O, S; n = 2 (dmapeE), E = O; Ar = o-N,N-dimethylanilinyl). The precursor, Pd[Cl.sub.2](dmapm), which exists in solution as an equilibrium mixture of the P,P- and P,N-ligated isomers, reacts with peroxides to form Pd[Cl.sub.2](P,N-dmapmO) and with sulphur to give [PdCl(P,N,S-dmapmS)]Cl, probably by direct oxidation of the "dangling" P atom of the P,N-isomer. Pd[Cl.sub.2](dmape), which exists in solution as a mixture of Pd[Cl.sub.2] (P,P-dmape) and [PdCl(P,P,N-dmape)]Cl, reacts with hydroxide in [H.sub.2]O-C[H.sub.2][Cl.sub.2] under argon to give the face-to-face [Pd(II).sub.2] complex containing the cation [[[[Pd.sub.2][Cl.sub.2]([micro]-P,N:O-dmapeO).sub.2]].sup.2+], which was isolated and crystallographically characterized as the P[F.sub.6] salt. The remarkable structure, consisting of two face-to-face Pd(II) square planes in a head-to-tail orientation, reveals a 12-membered ring containing the two non-bonded metal centres (Pd-Pd = 4.873(2) [Angstrom]). The dmapmS complex shows marginal activity as a catalyst for the hydration of maleic to malic acid. Key words: phosphine, phosphine oxide, phosphine sulphide, palladium. On decrit les complexes du palladium(II) de ligands bis(phosphine)monooxyde et bis(phosphine)monosulfure avec des composes de formule generale [[Ar.sub.2]P(C[H.sub.2]).sub.n]P(E)[Ar.sub.2] dans lesquels n = 1 (dmapmE), E = O, S; n = 2 (dmapeE), E = O; Ar = o-N,N-dimethylanilinyle. Le precurseur Pd[Cl.sub.2](dmapm), qui existe en solution sous la forme d'un melange a l'equilibre des ligands isomeres P,P et P,N, reagit avec les peroxydes pour former le Pd[Cl.sub.2](P,N-dmapmO) et avec le soufre pour donner le [PdCl(P,N,S-dmapmS)]Cl, probablement par une oxydation directe de l'atome de P qui se [??] balance [??] dans l'isomere P,N. Le Pd[Cl.sub.2](dmape), qui existe en solution sous la forme d'un melange de Pd[Cl.sub.2](P,P-dmape) et de [PdCl(P,P,N-dmape)]Cl, reagit avec l'ion hydroxyde dans un melange [H.sub.2]O-C[H.sub.2][Cl.sub.2], sous argon, pour conduire a la formation du complexe face a face [Pd(II).sub.2] contenant le cation [[[[Pd.sub.2][Cl.sub.2]([micro]-P, N:O-dmapeO).sub.2]].sup.2+] qui a ete isole et caracterise cristallographiquement sous la forme de sel de P[F.sub.6]. La structure remarquable, formee de deux Pd(II) plans carres, face a face et en position tete a queue, comporte un cycle a douze chainons avec deux centres metalliques non lies (Pd--Pd = 4,873(2) [Angstrom]). Le complexe dmapmS presente une activite marginale comme catalyseur pour l'hydratation de l'acide maleique en acide malique. Mots cles : phosphine, oxyde de phosphine, sulfure de phosphine, palladium. [Traduit par la Redaction]

A novel ruthenium-catalyzed tandem ring-closing metathesis (RCM) double-bond isomerization reaction is described. The utility of this method for the efficient syntheses of five-, six-, and seven-membered cyclic enol ethers is demonstrated.

Thiols mediate the radical isomerization of allylic amines into enamines. The reaction results in the cleavage of the allylic C-N bond, after treatment with HCl.

Studies of RNA polymerize in complexes with fork junction DNA under conditions where its isomerization is incomplete were conducted to define constitutes of isomerization. Studies demonstrate that nucleotides can stimulate the isomerization of RNA polymerase, which is reflected in an increase in the fraction of heparin-resistant complexes.

The zeolite interior is clearly able to enhance the power of a chiral auxiliary during reaction from excited singlet and triplet states are reported. The cations and confined space force the molecule to adopt a conformation, which results in a stronger interaction between the chiral center and the site of reaction present within a single molecule.