Preconcentration of gallium by coprecipitation with synthetic zeolites prior to determination by electrothermal atomic absorption spectrometry.

Synthetic zeolites were dissolved in nitric acid, and the resulting solution used as a coprecipitant for the preconcentration of trace amounts of gallium in water samples prior to determination by electrothermal atomic absorption spectrometry (ETAAS). The gallium preconcentration conditions and the ETAAS measurement conditions were optimized. Gallium was quantitatively concentrated with the zeolites coprecipitate from pH 6.0 to 8.0. The coprecipitate was easily dissolved in nitric acid, and an aliquot of the resulting solution was introduced directly into a tungsten metal furnace. The atomic absorbance of gallium in the resulting solution was measured by ETAAS. An ashing temperature of 400 degrees C and an atomizing temperature of 2600 degrees C were selected. The calibration curve was linear up to 3.0 microg of gallium and passed through the origin. The detection limit (S/N > or = 3) for gallium was 0.08 microg/100 cm3. The relative standard deviation at 1.0 microg/100 cm3 was 3.0% (n = 5). The proposed method has been successfully applied to trace gallium analysis in environmental water samples.     

Spectrophotometric determination of glucosamine and its analogous amino sugars with o-hydroxyhydroquinonephthalein and palladium(II).

A simple and highly sensitive spectrophotometric method for the determination of glucosamine and its analogous amino sugars was established based on fading of the palladium(II)-o-hydroxyhydroquinonephthalein-hexadecyltrimethylammonium complex. In the determination of glucosamine, Beer's law is obeyed in the range of 0.02 - 0.18 microg ml(-1), with an effective molar absorptivity at 630 nm and the relative standard deviation being 8.4 x 10(5) dm3 mol(-1) cm(-1) and 1.08% (n = 10). This method is about 70-times more sensitive than the Elson-Morgan method. The method was successfully applied to the assay of glucosamine in actual samples.     

Calorimetric study of the cubic mesogen,ACBC(16)

The heat capacity of the cubic mesogen ACBC(16) was measured between 16 and 500?K by adiabatic calorimetry. As well as the known condensed phases, a new crystalline phase was found to undergo a glass transition at around 165?K. Phase transitions between crystal, SmC, cubic, and isotropic liquid phases took place at 399.16, 431.15, and 474.30?K, respectively. As in the case of ANBC, a broad hump was observed in the heat capacity of the isotropic liquid phase. The first order nature of the SmC–cubic phase transition was confirmed for the first time by the observation of supercooling of the cubic phase. The broad hump in the isotropic liquid phase was shown to extend to a low temperature side if the isotropic liquid was supercooled, suggesting that the event occurring at the hump is not directly related to the cubic–isotropic liquid phase transition.     

Four new prostanoids: Claviridenone-A, -B, -C,and -D from the okinawan soft coral Clavularia viridis

The structures of four new prostanoids named claviridenone-a, -b, -c, and -d, which were isolated from the Okinawan soft coral Clavularia viridis, were elucidated as $\text{1}$, $\text{2}$, $\text{3}$, and $\text{4}$, respectively.     

HPLC analysis of manno-oligosaccharides derived from Saccharomyces cerevisiae mannan using an amino column or a graphitized carbon column

The chromatographic behavior of manno-oligosaccharides derived from Saccharomyces cerevisiae mannan on two kinds of HPLC columns, an aminopropyl-silica column or a graphitized carbon column (GCC), was investigated. The order of elution of manno-oligosaccharides on both columns with acetonitrile-water was almost the same, that is, the retention increased with increasing molecular size. However, the GCC made it possible to isolate completely two isomers of mannotrioses (M(3)-1 and M(3)-2) with different linkage positions. We reinvestigated the structures of mannobiose (M(2)), M(3)s, and mannotetraose (M(4)) that were completely isolated by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and NMR spectroscopy.     

Palladium charcoal-catalyzed Suzuki-Miyaura coupling to obtain arylpyridines and arylquinolines

A phosphine ligand, such as PPh3 or 2-(dicyclohexylphosphino)biphenyl, is essential for the Pd/C-catalyzed Suzuki-Miyaura coupling of halopyridines and haloquinolines, although it has been reported that the reaction of phenyl chlorides can be catalyzed by nonprereduced Pd/C without any additives. In the reactions of bromopyridines, bromoquinolines, 2-chloropyridines, and 2-chloroquinolines, PPh3 was effective enough to provide coupling products in good yields. However, in the reactions of 3-chloropyridine, 4-chloropyridine, and 6-chloroquinoline, sterically hindered 2-(dicyclohexylphosphino)biphenyl was indispensable as a ligand.     

Syntheses and reactions of some 2,3-disubstituted pyrazine monoxides

The reactions of 2,3-dimethyl- ( 4 ), 2,3-diphenyl- ( 6 ), and 2-methyl-3-phenyl-pyrazine monoxides ( 8 and 9 ) with phosphoryl chloride and acetic anhydride resulted in giving monochloro- and monacetoxy-pyrazines in almost all cases. However, the reaction of 6 with acetic anhydride afforded exceptionally a diacetoxydihydro-pyrazine. These products were converted further to hydroxy or dichloro derivatives.     

Discovery of a novel and potent human and rat beta3-adrenergic receptor agonist, [3-[(2R)-[[(2R)-(3-chlorophenyl)-2-hydroxyethyl]amino]propyl]-1H-indol-7-yloxy]acetic acid

In search for potent and selective beta3-adrenergic receptor (beta3-AR) agonists as potential drugs for the treatment of type II diabetes and obesity, a novel series of 1-(3-chlorophenyl)-2-aminoethanol derivatives were prepared and evaluated for their biological activity at human beta1-, beta2-, and beta3-ARs and rat beta3-AR expressed in Chinese hamster ovary (CHO) cells. Replacement of the right-hand side (RHS, benzene ring) in the 'first generation' beta3-AR agonists BRL 37344 and CL 316243 with a 1H-indole ring gave compound 31 with unique pharmacological properties among beta3-AR agonists. Initial in vitro assays showed that 31 possesses modest rat and human beta3-ARs agonistic activity. Introduction of various substituent into the indole nucleus of 31 afforded a number of compounds with good beta3-ARs agonistic activity. In particular, 90 having a carboxylic acid functionality at the 7-position of the indole nucleus showed the most potent human beta3-AR agonistic activity. Finally, optical resolution of 90 led to the identification of the most promising compound, [3-[(2R)-[[(2R)-(3-chlorophenyl)-2-hydroxyethyl]amino]propyl]-1H-indol-7-yloxy]acetic acid (96, AJ-9677). This compound exhibited potent human beta3-AR agonistic activity (EC50=0.062 nM, IA=116%) with 210- and 103-fold selectivity over human beta2-AR and beta1-AR, respectively. Compound 96 also exhibited potent rat beta3-AR agonistic activity (EC50=0.016 nM, IA=110%). Moreover, repeated oral administration of 96 inhibited body weight gain and significantly decreased glucose, insulin, free fatty acid, and triglyceride concentrations in plasma in KK-Ay/Ta mice. On the basis of this pharmacological profile, 96 entered clinical development as a drug for the treatment of type II diabetes and obesity.