Aryl-β-C-glucosidation using glucal boronate: application to the synthesis of tri-O-methylnorbergenin

Novel aryl-β-C-glucosidation method using glucal boronate was developed. This protocol can offer several advantages including use of non-toxic, easily handling glucal boronate as a crystalline solid and storable at room temperature for several months. Tri-O-methylnorbergenin (8,10-di-O-methylbergenin), an anti-HIV active bergenin derivative, was concisely synthesized by application of the aryl-β-C-glucosidation method.     

Effects of Bis(aromatic) Pendants on Recognition of Nucleobase Thymine by Zn2+ -1,4,7,10-tetraazacyclododecane (Zn2+ -cyclen)

We have previously shown that the nucleobase thymine binding to Zn²⁺ -cyclen (cyclen=1,4,7,10-tetraazacyclododecane) complex became stronger by appending acridine, naphthalene, or quinoline rings to the cyclen. Amongst these, the pendant bis((1-naphthyl)methyl) or bis((4-quinolyl)methyl) groups yielded the most effective thymine-recognizing Zn²⁺ -cyclen complexes [J. Am. Chem. Soc., 121 (1999) 5426]. The present study was undertaken to find causes of the bis(aromatic) ring effect by X-ray crystal structure analysis and NMR studies. The crystal structure of the Zn²⁺ -bis((1-naphthyl)methyl)-cyclen complex with a deprotonated 1-methylthymine (1-MeT) failed to show the anticipated evidence for the double ~ - ~ stacking interactions between the two naphthalenes and the Zn 2+ -bound 1-MeT m (1-MeT m =N(3')-deprotonated 1-MeT). Crystal data: formula C₃₆ H₄₇ N₇ O₇ Zn, M r =755.19, monoclinic, space group P2₁/ c (No. 14), a =15.438(2) Å, b =14.093(3) Å, c =16.726(2) Å, g =90.53(1) V =3638.7(8) Å 3 Z =4, R =0.035, R _w =0.049. However, the ¹H NMR studies of Zn²⁼ -bis((4-quinolyl)methyl)-cyclen with 1-MeT in varying H₂O/CH₃ CN solution showed increasing upfield shifts of Me(5') and H(6') of the Zn²⁺ -bound 1-MeT in more aqueous media, indicating that the double intercalation with the two quinolines became more significant in more protic environments. We conclude that the double ~ - ~ stacking effect accounts for the enhanced recognition of thymine base by the appended bis((1-naphthyl)methyl) or bis((4-quinolinyl)methyl) groups.     

pH-Responsive Phase Transition of Supramolecular Hydrogel Consisting of Glycosylated Amino Acetate and Carboxylic Acid Derivative

By addition of a carboxylated amino acetate (2) to a low-molecular-weight hydrogel (1) which has a unique thermally induced volume-phase transition character, a macroscopic pH-responsive feature is newly conferred on the supramolecular hydrogel. The direct observation of temperature-dependent behavior of the mixed hydrogel clearly showed that the thermally induced swelling-shrinkage type of the volume phase transition at pH 4 is shifted to the gel–sol transition at pH 7 by 10?mol% addition of 2 to the hydrogel 1. On the basis of the measurements by TEM, SEM, XRD and FT-IR, it is conceivable that incorporation of the anionic carboxylate of 2 slightly disturbs the packing of the hydrogen bond belt of the mixed hydrogel. Such a slight disturbance greatly leads to the sol–gel transition by elevating temperature, instead of the volume-phase transition. Introduction of dynamic characteristics to supramolecular systems in a macroscopic level may extend the potential of these materials in various fields.     

Organochlorine Pesticides in Water,Sediment and Fish from the Nile River and Manzala Lake in Egypt

Abstract

To assess the risks of organochlorine pesticides discharged into the hydrospheric environment of Egypt, river and lake water, drinking water, suspended solids, sediments and fish were collected during 1993—1994 from the Nile River and Manzala Lake in Egypt and were transported to Japan for chemical analysis. Among different organochlorine pesticides analyzed, p,p′-DDE was the most predominant in fish (7.6 to 67 ng/g wet wt.), sediments (3.2 to 432 ng/g dry wt.) and suspended solids (5.3 tc 138 pg/L). However, in the dissolved phase of water samples HCH compounds predominated (α-HCH, 71 to 2,815 pg/L). Concentrations of organochlorine pesticides, except chlordane, were higher in Manzala Lake than in the River Nile. Concentrations of organochlorine pesticides in fish corresponded with those in sediments from each location. Comparison of organochlorine concentrations in Nile River water with those reported in earlier studies suggested a decrease in concentrations during the last decade. However, concentrations of p,p′-DDE has increased in fish. It appears that the release of this metabolite from contaminated sediment is the major source of p,p′-DDE in fish during recent years.     

Ionic Conduction in Electrolyte Solution

The electrical conductivity in aqueous solutions of electrolytes has been obtained in terms of inter-particle potentials and pair distribution functions, based on a generalized Langevin equation for the cation and anion. This treatment allows us to connect and compare with the work of a computer simulation where the inter-particle potentials are the only input. The results for the concentration dependence of electrical conductivity are basically represented as a function of the square root of concentration. The electrophoretic and relaxation effects are discussed from a microscopic view point. The ionic hydration in electrolytic solution is also discussed. Available inter-particle potentials in aqueous solutions of electrolytes are proposed. The numerical application is carried out for sodium chloride and other aqueous electrolyte solutions.     

Recognition of caffeine by a water-soluble acyclic phane compound

Caffeine (1,3,7-trimethylxanthine) is a chemical substance associated with everyday human life. In order to recognize caffeine in water, six water-soluble acyclic phane compounds composed of three aromatic rings were examined as artificial receptors. ¹H NMR titration experiments revealed that 6,6′-[1,3-phenylenebis(carbonylimino)]bis-1,3-naphthalenedisulfonate had the highest binding ability for caffeine, with a binding constant (K_b) of 127±5 M⁻¹ at 300 K. While this phane compound also formed a complex with theophylline (1,3-dimethylxanthine) at around half the value of the binding constant for caffeine (K_b=64±4 M⁻¹), it showed weak or little complexation for adenosine, guanosine, inosine, and their 5′-phosphates (sodium salts of adenylic acid, guanylic acid, and inosinic acid).     

Protective Effect of Ferulic Acid against Hydrogen Peroxide Induced Apoptosis in PC12 Cells

Ferulic Acid (FA) is a highly abundant phenolic phytochemical which is present in plant tissues. FA has biological effects on physiological and pathological processes due to its anti-apoptotic and anti-oxidative properties, however, the detailed mechanism(s) of function is poorly understood. We have identified FA as a molecule that inhibits apoptosis induced by hydrogen peroxide (H₂O₂) or actinomycin D (ActD) in rat pheochromocytoma, PC12 cell. We also found that FA reduces H₂O₂-induced reactive oxygen species (ROS) production in PC12 cell, thereby acting as an anti-oxidant. Then, we analyzed FA-mediated signaling responses in rat pheochromocytoma, PC12 cells using antibody arrays for phosphokinase and apoptosis related proteins. This FA signaling pathway in PC12 cells includes inactivation of pro-apoptotic proteins, SMAC/Diablo and Bad. In addition, FA attenuates the cell injury by H₂O₂ through the inhibition of phosphorylation of the extracellular signal-regulated kinase (ERK). Importantly, we find that FA restores expression levels of brain-derived neurotrophic factor (BDNF), a key neuroprotective effector, in H₂O₂-treated PC12 cells. As a possible mechanism, FA increases BDNF by regulating microRNA-10b expression following H₂O₂ stimulation. Taken together, FA has broad biological effects as a neuroprotective modulator to regulate the expression of phosphokinases, apoptosis-related proteins and microRNAs against oxidative stress in PC12 cells.     

Analysis of the quantum numbers J(PC) of the X(3872) particle

We present an analysis of angular distributions and correlations of the X(3872) particle in the exclusive decay mode X(3872)-->J/psipi+ pi- with J/psi-->mu+ mu-. We use 780 pb-1 of data from pp[over ] collisions at sqrt[s]=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. We derive constraints on spin, parity, and charge conjugation parity of the X(3872) particle by comparing measured angular distributions of the decay products with predictions for different J(PC) hypotheses. The assignments J(PC)=1++ and 2-+ are the only ones consistent with the data.