Novel Enantioselective Synthesis of Both Enantiomers of Furan‐2‐yl Amines and Amino Acids

A new enantioselective synthesis of furan‐2‐yl amines and amino acids is described, in which the key step is the oxazaborolidine‐catalyzed enantioselective reduction of O‐benzyl (E)‐ and (Z)‐furan‐2‐yl ketone oximes to the corresponding chiral amines. The chirality of the furan‐2‐yl amines is fully controlled by the appropriate choice of the geometrical isomer of the O‐benzyl oxime. Oxidation of the furan ring furnished amino acids in high yields.     

Umsetzung von hydrobromiertem 1,4-Polybutadien mit lithiumorganischen Verbindungen

Ohne ZusammenfassungMit 1 Abbildung und 1 Tabelle     

Surface Characterization of Sepiolite by Inverse Gas Chromatography

Inverse gas chromatography (IGC) was applied to characterize the surface of sepiolite. The adsorption thermodynamic parameters (the standard enthalpy (ΔH ⁰), entropy (ΔS ⁰) and free energy of adsorption (ΔG ⁰)), the dispersive component of the surface energy (γ _S ^d ), and the acid/base character of sepiolite surface were estimated by using the retention time of different non-polar and polar probes at infinite dilution region. The specific free energy of adsorption (ΔG ^sp ), the specific enthalpy of adsorption (ΔH ^sp ), and the specific entropy of adsorption (ΔS ^sp ) of polar probes on sepiolite were determined. ΔH ^sp were correlated with the donor and modified acceptor numbers of the probes to quantify the acidic K _A and the basic K _D parameters of the sepiolite surface. The values obtained for the parameters K _A and K _D indicated an acidic character for sepiolite surface.     

Novel dye-attached macroporous films for cadmium, zinc and lead sorption: Alkali Blue 6B-attached macroporous poly(2-hydroxyethyl methacrylate)

Alkali Blue 6B-attached poly(2-hydroxyethyl methacrylate) (poly(HEMA)) microporous films were investigated as chelate forming sorbents for heavy metal removal. Poly(HEMA) microporous films were prepared by UV-initiated photo-polymerization of HEMA in the presence of an initiator (azobisisobutyronitrile (AIBN)). Alkali Blue 6B was attached covalently. These films with a swelling ratio of 58%, and carrying 14.8 mmol Alkali Blue 6B m(-2) which were then used in the removal of Cd(II), Zn(II) and Pb(II) from aqueous media. Adsorption rates were very high, equilibrium was achieved in about 30 min. The maximum adsorption of heavy metal ions onto the Alkali Blue 6B-attached films were 41.4 mmol m(-2) for Cd(II), 52.4 mmol m(-2) for Zn(II), and 64.5 mmol m(-2) for Pb(II). When the heavy metal ions competed during the adsorption from a mixture the adsorption values for Cd(II), Zn(II) and Pb(II) were quite close. Heavy metal ions were desorbed by using 0.1 M HNO(3). A significant amount of the adsorbed heavy metal ions (up to 95%) could be desorbed in 30 min. Repeated adsorption/desorption cycles showed the feasibility of these novel dye-attached microporous films for heavy metal removal.     

Observations on clear solution silicalite-1 growth by nanoslabs

Several research groups have reported the presence of nanometer-sized particles (nanoslabs) in clear solutions, which precipitate the crystalline MFI (ZSM-5) structure. Debate about the growth mechanism for Al-free ZSM-5 (silicalite-1) has revolved around growth by small silicate units (monomers, dimers, etc.) from solution vs growth by nanoslab addition. A model developed for precipitation of uniform sized colloids by addition of sub-colloidal precursor units has been adapted for this zeolite synthesis system. Parameter values were adjusted for the simulation results to match experimental observations from work reported previously, at least to the extent possible. The model involved the simultaneous solution of up to 6000 ordinary differential equations, and required computation times of up to 24 h. The results shed light on the crystal growth mechanism, but pose questions for further investigations of the nucleation mechanism.     

Redox behaviour of cysteine in the presence of ammonium trioxovanadate(V)

The interaction of ammonium trioxovanadate(V) with cysteine in aqueous solution was studied by cyclic voltammetry and absorption spectroscopy techniques. In the absence of cysteine, the cyclic voltammogram (CV) of ammonium trioxovanadate(V) solution in 0.1 M phosphate buffer (pH 7) gave two peaks at -0.130 V (reversible) and -0.400 V (irreversible). These peaks (-0.130 V, -0.400 V) can be attributed to V(V)/V(IV) and V(IV)/V(III) redox processes, respectively. In the presence of cysteine at low scan rate (40 mV/s), the peak at -0.780 V, which is assigned to the irreversible reduction of free cystine, was observed. In addition, the reduction peak of the disulfidic anion S(2)(2-) was seen at -0.650 V. Under aerobic conditions, the peaks of the disulfidic anion S(2)(2-) and free cystine are well separated. From electronic spectra of ammonium trioxovanadate(V) and cysteine mixtures, LMCT transition associated with V(V)-cyteine complex was obtained at 743 nm. The stoichiometry (ML(2)) and stability constant (log beta(1:2)=6.67) of V(V)-cysteine complex were determined by means of mole ratio method.     

Determination of carvedilol in human cardiac tissue by high-performance liquid chromatography

A new high-performance liquid chromatographic method has been developed for the determination of the beta-receptor blocker carvedilol in human cardiac tissue. After homogenizing tissue samples in a microdismembrator, carvedilol and the internal standard naftopidil are extracted with acetone. The extract is evaporated to dryness and reconstituted in a potassium acetate buffer of pH 3.5. Samples are cleaned up with solid-phase extraction columns. Carvedilol and the internal standard show recoveries of 69.8 +/- 12.2% and 63.9 +/- 9.34%, respectively. The linearity range for carvedilol is 0.01-0.35 ng/mg (parts per billion) tissue (wet weight), and the limit of quantitation is 0.01 ng/mg. The percentage coefficient of variation of the intra-assay varies between 1.45 and 5.38% and the interassay between 4.25 and 6.96%. To use as an application of the assay, the cardiac carvedilol tissue level in a patient on oral carvedilol therapy for congestive heart failure is reported.