Synthesis and Tunable Optical Properties of C,N-Chelated Borate Luminophores Derived from Potassium Acyltrifluoroborates

A new class of borate luminophores has been synthesized by a simple two-step reaction using potassium acyltrifluoroborates (KATs) as starting materials. The hydrazones obtained from reactions between KATs and 2-hydrazinopyridines followed by a cyclization resulted in the unprecedented formation of C,N-chelated six-membered bora-heterocycles. Under consideration of the results of DFT and TD-DFT calculations, four luminophores based on such bora-heterocycles are designed and synthesized, which exhibit a tunable fluorescence range from blue to red in the solid state. Moreover, one of the luminophores exhibits mechanofluorochromism from blue to yellow/green. As a result of the aforementioned mechanochromism of one of these luminophores, white-color emission was achieved by simply mixing the four luminophores.     

Stereoselective synthesis of β-fluoroallyl alcohols

β-Fluoroallyl alcohols ($\text{6}$) were obtained with high stereoselectivity by the LiA1H₄ reduction of 1-acetoxy-3-alkyl-2,2-difluorocyclopropanes ($\text{5}$).     

The study on phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis: synthesis of homogeneous substrates, substrate specificity and other properties.

The properties of phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis were studied in detail. The enzyme was extremely thermostable in 0.1% bovine serum albumin and retained 73% of its activity at 100 degrees C for 10 min, while it was labile in the absence of albumin. The enzymatic activity was inhibited by HgCl2 or p-chloromercuriphenylsulfonic acid and restored by dithiothreitol. The kinetic parameters (Km and Vmax) of PI-PLC were determined for the mixed micelle of yeast phosphatidylinositol (PI)/Triton X-100 or sodium deoxycholate. Four PIs having different acyl chains: dilauroylphosphatidylinositol (DLPI), dimyristoylphosphatidylinositol (DMPI), dipalmitoylphosphatidylinositol (DPPI) and dioleoylphosphatidylinositol (DOPI) were synthesized from yeast PI through the processes of deacylation and reacylation, identified by infrared (IR) and Fourier transform nuclear magnetic resonance (FT-NMR) spectra, and subjected to the action of PI-PLC. All the synthetic PIs were hydrolyzed by this enzyme, with DLPI and DMPI being the best substrates. PI-PLC did not catalyze the hydrolysis of the phosphatidylnucleosides 5'-phosphatidylcytidine, 5'-phosphatidyluridine, 5'-phosphatidylthymidine, 5'-phosphatidyladenosine and 5'-phosphatidyl-2'-deoxyadenosine.     

Phospholipase D modified with a polyethylene glycol derivative

Phospholipase D from Streptomyces sp. AA586, PLDP, was modified with methoxypolyethylene glycol succinimidylsuccinate (ss-PEG), an active derivative of polyethylene glycol. By titration with trinitrobenzene sulfonate (TNBS), approximately 70% of the free amino groups in the enzyme protein were shown to be modified by treatment with ss-PEG. By this modification, the molecular weight of the enzyme was increased, judging from the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, gel filtration with Toyopearl HW-55F and TNBS titration. Due to loss of cationic charges, the enzyme protein became eluted faster in high performance liquid chromatography with CM-Toyopearl. By modification with ss-PEG, the enzyme became fairly thermostable, while pH-stability and optimal pH were not influenced. The value of Km for phosphatidylcholine of the hydrolytic reaction increased 2-fold, whereas that of the transphosphatidyl reaction was not significantly altered.     

Effect of GeIon on Electrical Properties of (La0.1Ca0.9)(Mn1−xGex)O3

Orthorhombic perovskite-type (La_0.1Ca_0.9)(Mn_1−xGe_x)O₃was synthesized in the range (0.00≤x≤0.10). Since the ionic radius of the Ge⁴⁺ion is equal to that of the Mn⁴⁺ion, the (Mn, Ge)–O(1, 2) distances and the angles for (Mn, Ge)–O(1, 2)–(Mn, Ge) are independent of the composition (x). From the measurement of the electrical resistivity (ρ), all manganates exhibit a metal–insulator transition. With increasingx, the metal–insulator transition temperature (T_t) increases anddρ/dTdecreases. The cation–anion–cation overlap integrals are weakened by the Ge⁴⁺ion.     

The structures of noncyclic polyether carriers exhibiting lithium ion-selective transport

Several noncyclic polyether compounds containing oxytrimethylene groups and o-carboxyphenyl terminal group were synthesized. It has been found that they can transport lithium ion selectively in the competitive alkali metal ion transport through liquid membranes. The results of the spectroscopic study, together with inspection on the basis of the CPK model building suggest that these polyethers can form a pseudocavity, in which lithium ion best fits, and then the terminal aromatic rings overlap one another face-to-face to form a stacking structure. By using newly synthesized polyethers, which were designed on the basis of the conformational information, the significant contribution of the structures of these polyethers could be verified.     

Enantioselective tandem O-nitroso Aldol/Michael reaction

This communication presents studies that illustrated nitroso Diels-Alder adduct has been obtained in uniformly high enantioselectivity via a tandem nitroso aldol/Michael reaction using an amine catalyst. The regiochemical outcome of this construction is documented to be the opposite to that of the normal nitroso aldol reaction, which has been determined by X-ray analysis. The reaction of the enone with silver-BINAP catalyst has also been investigated in conjunction with the control of regiochemistry in a stepwise process.     

Copper-catalyzed allylations of zirconocene intermediates generated from o-alkenyl or o-alkynylbenzyl ether derivatives and zirconocene-butene complex

o-Alkenyl or alkynyl benzylzirconocene intermediate, which was readily generated by the reaction of 2-alkoxymethylstyrene or 2-alkoxymethyl-1-(trimethylsilylethynyl)-benzene derivative with zirconocene-butene complex (Negishi reagent, "Cp2Zr"), reacted with allyl or propargyl halides in the presence of a catalytic amount of CuCl to give allylation or allenylation products. Conversion to Dane's diene, which is a key intermediate for estrone synthesis, was efficiently carried out by enyne olefin metathesis of the allylation products.     

Spectrophotometric determination of manganese with 1-(2-pyridylazo)-2-naphthol and a non-ionic surfactant

A spectrophotometric method for the determination of trace amounts of manganese with 1-(2-pyridylazo)-2-naphthol (PAN) is described. The method is based on the measurement of absorbance of the manganese—PAN chelate solubilized with a non-ionic surfactant, Triton X-100. No extraction procedure is required in the method proposed. High concentrations of calcium, aluminium and magnesium do not interfere. The presence of up to 10 ppm of lead can be tolerated. Iron, cadmium, zinc, cobalt and nickel can be effectively masked with potassium cyanide. Beer's law is obeyed up to 2 ppm of manganese. The molar absorptivity of the manganese—PAN chelate found was 4.4 × 10⁴ l. mole ⁻¹. cm⁻¹ at 562 nm. The overall stability constant of Mn(PAN)₂ in 0.4% Triton X-100 medium is 10^16.8.