Effects of halogen substitution in nucleic acid components. Structure of sodium 5-bromocytidine 5'-phosphate hydrate

The conformation of 5-bromocytidine 5'-monophosphate in the title compound, Na+.C9H11BrN3O8P-.1.25H2O, is anti, C(3')-endo and gauche-gauche, similar to that in analogous non-halogenated nucleosides/nucleotides. The Na ion coordinates directly with phosphate O atoms and base atoms. Br is not involved in any stacking interaction.

Miscibility of Poly(aromatic acrylate)s and Methacrylates with Styrene/Acrylonitrile copolymers

Miscibilities of some poly[aromatic (meth)acrylatels namely, poly(pheny1 acrylate) (PPA), poly(pheny1 methacrylate) (PPMA), poly(benzy1 acrylate) (PBA), and poly(benzy1 methacrylate) (PBMAY polystyrene blends, have been studied through the so-called copolymer effect by incorporating acrylonitrile units in PS chains. In these systems, miscibility occurs on account of the strong repulsion between the acrylonitrile and styrene units in the copolymer. PBA and PBMA were blended with different styreneacrylonitrile (SAN) copolymers. A miscibility window has been identified for the latter system, and from these limits, the binary interaction energy density parameters (B,j.’sw) ere calculated. Using these values, the miscibilities in other homopolymer-copolymer and copolymer-copolymer systems containing benzyl methacrylate, acrylonitrile, and styrene monomer units have been predicted and subsequently verified experimentally. The miscibility window limits in poly[aromatic (meth)acrylate]s/SAN copolymer blends have been compared. PBA does not exhibit a miscibility window with SAN copolymers, which has been explained by the weak intramolecular hydrogen bonding in PBA. The miscibility window in the PBW SAN copolymer system, as observed by DSC, shows a considerable narrowing in nonradiative energy transfer (NRET) measurements, as this technique is more sensitive.

Miscibility of poly(aromatic acrylate)s and methacrylates with styrene/acrylonitrile copolymers

Miscibilities of some poly[aromatic (meth)crylate]s namely, poly(phenyl acrylate) (PPA, poly(phenyl methacrylate) (PPMA), poly(benzyl acrylate) (PBA), and poly(benzyl methacrylate) (PBMA)/polystyrene blends, have been studied through the so-called copolymer effect by incorporating acrylonitrile units in PS chains. In these systems, miscibility occurs on account of the strong repulsion between the acrylonitrile and styrene units in the copolymer. PBA and PBMA were blended with different styrene-acrylonitrile (SAN) copolymers. A miscibility window has been identified for the latter system, and from these limits, the binary interaction energy density parameters (Bij's) were calculated. Using these values, the miscibilities in other homopolymer-copolymer and copolymer-copolymer systems containing benzyl methacrylate, acrylonitrile, and styrene monomer units have been predicted and subsequently verified experimentally. The miscibility window limits in poly[aromatic (meth)acrylate]s/SAN copolymer blends have been compared. PBA does not exhibit a miscibility window with SAN copolymers, which has been explained by the weak intramolecular hydrogen bonding in PBA. The miscibility window in the PBMA/SAN copolymer system, as observed by DSC, shows a considerable narrowing in nonradiative energy transfer (NRET) measurements, as this technique is more sensitive.

Effect of substitution of Y on the structural, magnetic, and thermal properties of hexagonal DyMnO3 single crystals

We investigate the structural, magnetic, and specific heat behavior of the hexagonal manganite Dy0.5Y0.5MnO3 in order to understand the effect of dilution of Dy magnetism with nonmagnetic yttrium. In this compound, the triangular Mn lattice orders antiferromagnetic at T-N(Mn) approximate to 68 K observed experimentally in the derivative of magnetic susceptibility as well as in specific heat. In addition, a low-temperature peak at T-N(Dy) similar to 3 K is observed in specific heat which is attributed to rare earth order. The T-N(Mn) increases by 9 K compared to that of hexagonal (h) DyMnO3 while T-N(Dy) is unchanged. A change in slope of thermal evolution of lattice parameters is observed to occur at temperature close to T-N(Mn). This hints at strong magnetoelastic coupling in this geometric multiferroic. In magnetization measurements, steplike features are observed when the magnetic field is applied along the c axis which shift to higher fields with temperature and vanish completely above 40 K. The presence of different magnetic phases at low temperature and strong magnetoelastic effects can lead to such field-induced transitions which resemble metamagnetic transitions. This indicates the possibility of strong field-induced effects in dielectric properties of this material, which is unexplored to date.

Synthesis, glucose uptake activity and structure-activity relationships of some novel glitazones incorporated with glycine, aromatic and alicyclic amine moieties via two carbon acyl linker

Three series of novel glitazones were designed and prepared by using appropriate synthetic schemes to incorporate glycine, aromatic and alicyclic amines via two carbon linker. Compounds were synthesized both under conventional and microwave methods. Nineteen out of twenty four synthesized compounds were evaluated for their in vitro glucose uptake activity using isolated rat hemi-diaphragm. Compounds, 6, 9a, 13a, 13b, 13c, 13f and 13h exhibited significant glucose uptake activity. Illustration about their synthesis and in vitro glucose uptake activity is described along with the structure activity relationships. (C) 2010 Elsevier Masson SAS. All rights reserved.

Reactions of the hexachlorocyclodiphosphazane [MeNPCl3]2 with primary aromatic amines: formation of highly basic bisphosphinimines

Reactions of hexachlorocyclodiphosphazane [MeNPCl3]2 with primary aromatic amines afforded the bisphosphinimine hydrochlorides [(RNH)2(RN)PN(Me)P(NHMe)(NHR)2]+Cl- (R = Ph 1, C6H4Me-4 2 or C6H4OMe-4 3). Dehydrochlorination of 2 and 3 by methanolic KOH yielded highly basic bisphosphinimines [(RNH)2(RN)PN(Me)P(NMe)(NHR)2] (R = C6H4Me-4 4 or C6H4OMe-4 5). Compounds 1-5 have been characterised by elemental analysis and IR and NMR (H-1, C-13, P-31) spectroscopy. The structure of 2 has been confirmed by single-crystal X-ray diffraction. The short P-N bond lengths and the conformations of the PN, units can be explained on the basis of cumulative negative hyperconjugative interactions between nitrogen lone pairs and adjacent P-N sigma* orbitals. Ab initio calculations on the model phosphinimine (H2N)3P=NH and its protonated form suggest that (amino)phosphinimines would be stronger bases compared to many organic bases such as guanidine.

Studies in crystal engineering: Effect of fluorine substitution in crystal packing and topological photodimerization of styryl coumarins in the solid state

Styryl coumarins generally yield centrosymmetric (alpha-mode, anti-HT) photodimers when subjected to irradiation in the solid state, However, the substitution of fluorine dramatically alters the packing mode and steers the molecules 4-(4-fluorostyryl)coumarin 1 and 4-(2-fluorostyryl)coumarin 2 to form a stereospecific photodimer, beta-mode, syn-HH across the styrenic double bond (yield 78-85%). The stereochemistry of the photodimer 2a has been established by X-ray crystallography. There is no evidence for the presence of C-H ... F interactions. The true nature of the weak atom-atom interactions called into play when fluorine is substituted is not clear, It is observed that the fluoro substituted compounds have greater crystal density than the corresponding unsubstituted ones.

Substitution of chromium for univalent copper in superconducting Pb2Sr2(Ca,Y)Cu3O8+delta

Following considerations of geometry and the similarity between chromate and carbonate groups in terms of size and charge, we have investigated the possibility of replacing the two-coordinate Cu-I in superconducting lead cuprates of the general formula Pb2Sr2(Ca, Y)CU3O8 by Cr. A high-resolution electron microscopy study coupled with energy dispersive X-ray analysis on small crystals of the title phases suggests that between 10 and 15% of the Cu-I can be replaced by Cr. While from the present structural study using HRTEM and Rietveld refinement of X-ray powder data we are unable to precisely obtain the oxidation state and oxygen coordination of Cr, we suggest in analogy with Cr substitution in other similar cuprates that in the title phases (CuO2)-O-I rods are partially replaced by tetrahedral CrO42- groups. Infrared spectroscopy supports the presence of CrO42- groups. The phases Pb1.75Sr2Ca0.2Y0.8O8+delta and Pb1.75Sr2Ca0.2Y0.8CCu2.85Cr0.15O8+delta are superconducting as-prepared, but the substitution of Cr for Cu-I results in a decrease of the Te as well as the superconducting volume fraction. (C) 1996 Academic Press, lnc.

First-order hyperpolarizabilities of octupolar aromatic molecules: symmetrically substituted triazines

The first hyperpolarizabilities of some symmetrically substituted triazines have been measured and compared with those of the corresponding symmetrically substituted benzenes. The octupolar triazines have higher quadratic polarizabilities than the corresponding octupolar benzenes. The triazine ring seems to be a better central acceptor than the benzene ring, but if it acts as a donor as in sym-triphenyl triazine, the nonlinearity improves further.

Synthesis Based on Cyclohexadienes. 5. A New Approach to the Synthesis of a-Ring Aromatic Steroids - a Formal Total Synthesis of (+/-)-Estrone

A new strategy for the construction of A-ring aromatic steroids which resulted in the formal total synthesis of estrone is described. Thus reaction of the adduct (9), obtained from 1-methoxy-4-methylcyclohexa-1,4-diene and acrolein, with 3-(m-methoxyphenyl)propylmagnesium bromide followed by oxidation afforded the bicyclo[2.2.2]octene derivative (14). Acid-catalysed rearrangement of (14) followed by an intramolecular Michael addition resulted in the cis tetraenone (18) which was dehydrogenated with palladium chloride to the pentaenone (22). Li/NH3 reduction of (22) gave 3-methoxy-D-homoestra-1,3,5(10)-trien-16-one (31) which has been converted into the methyl ether (37) of marrianolic acid, and its methyl ester (38).

Surfactant lipids containing aromatic units produce vesicular membranes with high thermal stability

Six new vesicle-forming, cationic surfactant lipids are synthesized. Four of them contain 'flat' aromatic units at different locations of hydrophobic segments. In order to estimate the influence of aromatic units in the lipid monomer two other surfactant lipids of related structure with n-butyloxy units in the places of aromatic groups were also prepared. Transmission electron microscopy confirmed the vesicular membrane formation from these newly synthesized lipids. DSC or temperature-dependent keto-enol tautomerism of benzoylacetanilide-doped vesicles reveal a remarkable increase in the thermal stability of the membranes formed from aromatic surfactant lipids in contradistinction to their counterparts that contain n-butyloxy units. The enhanced thermal stability originates presumably as a consequence of inter-monomer stacking.

On the water-induced critical double point in a polymer solution: the role of isotopic substitution

This paper examines the effect of substitution of water by heavy water in a polymer solution of polystyrene (molecular weight = 13000) and acetone. A critical double point (CDP), at which the upper and the lower partially-miscible regions merge, occurs at nearly the same coordinates as for the system [polystyrene + acetone + water]. The shape of the critical line for [polystyrene + acetone + heavy water] is highly asymmetric. An explanation for the occurrence of the water-induced CDP in [polystyrene + acetone] is advanced in terms of the interplay between contact energy dissimilarity and free-volume disparity of the polymer and the solvent. The question of the possible existence of a one-phase hole in an hourglass phase diagram is addressed in [polystyrene + acetone + water]. Our data exclude such a possibility.

Nematogens with more flexible chains than aromatic rings in the core

Mesogens containing four rings in the main core can accommodate one terminal and two nearby lateral chains on each outside aromatic ring. These compounds containing six chains present an enantiotropic nematic range which is influenced by the rigidity of the links. The conformational behaviour of the first methyleneoxy group within the chains was investigated by one and two dimensional C-13 NMR. The sign of the jump in chemical shifts when entering the nematic phase indicates the folding of each lateral branch. Dipolar oscillations during cross-polarization contact provide the values of the bond order parameter. The two First lateral fragments do not behave in the same way, demonstrating the influence of the fragment along which the chain is back: folded.

Effect of Zr4+-ion substitution in CeO2 on H2O2-assisted degradation of orange G

A series of Pd ion-substituted CeO2-ZrO2 solid solutions were synthesized using the solution combustion technique. H2O2-assisted degradation of orange G was carried out in the presence of the catalysts. The activity of the catalysts was found to increase with the introduction of the second component in the solid solution, as signified by an increase in the rate constants and lowering of activation energy. The study showed the involvement of lattice oxygen and the importance of reducibility of the compound for the reaction. (C) 2011 Elsevier B.V. All rights reserved.

An enantiospecific approach to 8,9-seco-C-aromatic taxanes

An enantiospecific approach to functionalised C-aromatic-8,9-seco-taxanes starting from the readily available monoterpene (R)-carvone is described.