Enantioselective spiro ene-carbocyclization of 1,6-enynes catalyzed by tropos rhodium(I) complex with skewphos ligand

A tropos rhodium(I) complex having skewphos ligand is shown to be a highly enantioselective catalyst for asymmetric ene-type carbocyclization of 1,6-enynes with tri-substituted olefins to control quaternary stereogenic centers or spiro-rings.     

DNA cleavage induced by thermal electron transfer from a dimeric NADH analogue to acridinium ions in the presence of oxygen

Acridinium ions, which can intercalate to DNA, act as thermal DNA cleavers in the presence of a dimeric NADH analogue and O2 in an aqueous solution via thermal electron transfer from a dimeric NADH analogue to acridinium ions, followed by the electron-transfer reduction of O2 to O2*- by the resulting NAD radicals.     

Dynamics of molecular oxygen in micellar solutions

Fluorescence quenching by molecular oxygen has been employed to estimate dynamic parameters and solubility characteristics of molecular oxygen in micelle forming detergent solutions. A kinetic model which assumes that oxygen quenching occurs only in the micellar phase is employed to analyze the data.     

Determination of urea by ion chromatography with an immobilized urease reactor

An immobilized urease reactor can be used with ion chromatography for the simultaneous determination of urea, and sodium, potassium and ammonium ions. The conversion of urea to ammonium ion was found to be 76.5%. The calibration graph for urea was linear over the range 1 × 10^?5?1 × 10^?3 M (RSD 3%). The method was applied to human urine and a chemical fertilizer.     

Fluorescence maxima of 10-methylacridone-metal ion salt complexes: a convenient and quantitative measure of lewis acidity of metal ion salts

Aromatic carbonyl compounds such as 10-methylacridone form the Lewis acid complexes including paramagnetic and redox active Lewis acids. The fluorescence energies of the Lewis acid complexes are well correlated with the O2*--Lewis acid complexes derived from the gzz-values of the ESR spectra of the superoxide anion-Lewis acid complexes, thus providing a quantitative measure of the Lewis acidity.     

Diastereoselective allylations of allyl-propargyl hybrid cations: synthesis of conjugated 1,5-dien-7-yne frameworks bearing C(4)-stereogenic centers

[reaction: see text] Chiral C(4)-substituted (E)- or (Z)-1-alkynyl-1-trimethylsilyloxy-2-butene systems provide anti-(Z) or syn-(Z) conjugated dienyne, with a very high level of stereocontrol, on treatment with BF(3).OEt(2) in CH(2)Cl(2) at -50 degrees C in the presence of allyltrimethylsilane. The Cieplak conformation for (E)-substrates and neighboring-group participation for (Z)-substrates are considered to be responsible for the stereochemical consequences.