Conductance of the hydroxide ion intert-butyl alcohol-water and 1,4-dioxane-water mixtures

Limiting molar conductances λ_o of potassium hydroxide in 2 to 25 mol%tert-butyl alcohol (TBA)-water mixtures were determined at 25°C as a function of pressure up to 196 MPa. λ_o’s of KOH in (2.5 to 15 mol%) 1,4-dioxane-water mixtures at 25°C and 1 atm were also determined. The excess conductance λ _o ^e of the OH^- ion estimated as [λ _o ^e (OH^-) = λ_o(KOH) - λ_o(KCl)] decreased with an increase in the TBA or dioxane content, as did the excess proton conductance λ _o ^e (H⁺) [λ _o ^e (H⁺) = λ_O(HC1) - λ_o(KCl)]. Although λ _o ^e (OH^-) is smaller than λ _o ^e (H⁺) at all solvent compositions studied, the rate of decrease in λ _o ^e with organic content is larger for the OH^- ion than for the H₃O⁺ ion in both solvent mixtures except in the water-rich region of TBA-water mixtures. λ _o ^e (OH^-) increases with pressure more strongly in TBA-water mixtures than in pure water, and the rate of increase in λ _o ^e (OH^-) with pressure has a maximum at 5 mol% of TBA. These results are discussed in terms of the difference in stability of hydrogen bonds between the OH^- or the H₃O⁺ ion and water molecules and the increase in repulsive forces due to the orientation [H-O O-H] of water molecules in the mixtures.     

The synthesis of benzofuroquinolines. III. Two dihydroxybenzofuroquinolinones

Two dihydroxybenzofuroquinolinones, 3,9-dihydroxy-5H-benzofuro[3,2-c]quinolin-6-one (V) and 3,8-dihydroxy-6H-benzofuro[2,3-b]quinolin-11-one (VI), were obtained by the demethyl-cyclization of 3-(2,4-dimethoxyphenyl)-4-hydroxy-7-methoxy-1H-quinolin-2-one (IV). By the methylation with diazomethane, V gave a dimethylated compound (VII), while VI gave a trimethylated compound (VIII).     

Fast atom bombardment mass spectral study of tetracycline antibiotics

In the fast atom bombardment mass spectra of tetracyclines, ammonia elimination fragment ions, [M + H – NH₃]⁺ and [M + H – NH₃ – H₂O]⁺, appeared with considerable abundances. A plausible mechanism for the loss of ammonia from [M + H]⁺ was discussed based on results by measurements on various types of tetracyclines and benzamides as the model compounds and B/E linked scanning. The results indicated that the loss of ammonia occurred in the carboxyamide moiety in the A ring and was accelerated by an ortho-hydroxy group. The same fragmentations were observed in the electrospray mass spectra of tetracyclines with a skimmer-capillary voltage differential of 150 V.     

Helical polymer carrying helical grafts from peptide-based acetylene macromonomers: synthesis

N-Propargylamide-terminated peptide-based macromonomers with a degree of polymerization ranging from 4 to 40 were synthesized by the polymerization of gamma-benzyl and gamma-stearyl-L-glutamate-N-carboxy anhydrides initiated with propargylamine. The macromonomers took an alpha-helical structure, which was confirmed by signals at 208 and 220 nm in CD spectra. The macromonomers were subjected to polymerization and copolymerization with an alanine-derived N-propargylamide [N-(tert-butoxycarbonyl)-L-alanine-N'-propargylamide] catalyzed with (2,5-norbornadiene)Rh+[eta6-C6H5B- (C6H5)3]. It was confirmed through a CD spectroscopic study that the copolymer obtained from the copolymerization of the gamma-stearyl-L-glutamate-based macromonomer with the alanine-derived N-propargylamide had a helical polyacetylene main chain and helical polypeptide side chains.     

Rat liver and kidney catechol-O-methyltransferase activity measured by high-performance liquid chromatography with fluorescence detection

We have previously reported a highly sensitive method for the measurement of catechol-O-methyltransferase (COMT) activities in rat erythrocytes with norepinephrine (NE), an endogenous native substrate, using high-performance liquid chromatography (HPLC)-fluorescence or peroxyoxalate chemiluminescence reaction detection. Applying this method to COMT activities in rat liver and kidney, known to have the highest activities of all organs, the optimum reaction conditions were investigated. Under the optimum conditions, soluble (S)-COMT and membrane-bound (MB)-COMT activities in rat liver, with NE as a substrate, were 2.17 +/- 0.33 and 0.16 +/- 0.02 nmol/min/mg protein (n = 5), respectively. In rat kidney, S-COMT and MB-COMT activities were 1.81 +/- 0.20 and 0.079 +/- 0.009 nmol/min/mg protein (n = 5), respectively. Since liver and kidney play important roles in inactivating catecholamines, using the proposed method would yield critical information to delineate the role of metabolism of catecholamines in rat tissues.     

Polymerization of silicon-containing acetylenes. 5. Polymerization of 1-silyl-1-propynes by TaCl5-based catalysts

Polymerization of homologues of 1-(trimethylsilyl)-1-propyne [CH₃C?CSi(CH₃)₃] was studied. CH₃C?CSi(CH₃)₂(n-C₆H₁₃) ( I ) polymerized with 1 : 1 mixtures of TaCl₅ and organometallic cocatalysts (e.g., Ph₄Sn and Ph₃Bi) to produce in good yields a polymer having a weight-average molecular weight (M _w) over 1 × 10⁶. CH₃C?CSi(CH₃)₂ Ph ( II ) and CH₃C?CSi(C₂H₅)₃ ( III ) formed polymers having M _w's of ～ 5 × 10⁵ in moderate yields in the presence of TaCl₅-based catalysts. In contrast, none of CH₃C?CSi(CH₃)₂(i-C₃H₇), CH₃C? CSi(CH₃)₂(t,-C₄H₉), C₂H₅C?CSi(CH₃)₃, and n,-C₄H₉C?CSi(CH₃)₃ polymerized, which is attributed to the steric effect of the monomers. Some other 1-silyl-1-propynes also failed to polymerize. The three new polymers formed from ( I )–( III ) had the structure \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} [{\rm CCH}_{\rm 3} \hbox{=\hskip-2pt=} {\rm C(SiRR'R''}\rlap{--} ]_n$\end{document} according to IR and ¹³C-NMR spectra. They were white solids, soluble in low-polarity solvents (e.g., toluene and chloroform) and stable enough in air at room temperature.     

Self-assembled monolayer electrode of a diiron complex with a phenoxo-based dinucleating ligand: observation of molecular oxygen adsorptionldesorption in aqueous media

The phenoxo-based dinucleating ligand, 2,6-bis[bis(6-pivalamido-2-pyridylmethyl)amino-methyl-4-aminophenol (1), and its Fe2(II) complex, [Fe2(II)(1)(PhCOO)2](CF3SO3) (2), were prepared and 2 deposited on the Au surface (2/Au) is much more stable than in solution and exhibits redox behavior in aqueous media as well as reversible adsorption/desorption of oxygen at room temperature.     

Copper-catalyzed synthesis of esters from ketones. Alkyl group as a leaving group

The conversion of ketones to esters has been achieved through the use of Cu catalyst and tetrabutylammonium nitrite. This reaction involves the activation of the less activated C-C bond, and the alkyl group is removed as a leaving group. Various isopropyl ketones are found to be good substrates for this reaction.     

Development and validation of bioanalytical methods for imidafenacin (KRP-197/ONO-8025) and its metabolites in human urine by using liquid chromatography-tandem mass spectrometry

New bioanalytical methods have been developed for the determination of imidafenacin (KRP-197/ONO-8025, IM), a novel antimuscarinic drug developed for the treatment of overactive bladder, and its metabolites, M-2, M-3, M-4, M-6 and M-8 (method 1), M-5 and M-9 (method 2) in human urine by using liquid chromatography-tandem mass spectrometry. In each method, the urine sample was extracted by solid-phase extraction, separated on a semi-micro high-performance liquid chromatography column using gradient elution and detected by tandem mass spectrometer with an atmospheric pressure chemical ionization or ionspray interface. Extraction recoveries of IM and metabolites were 81.4% or more. Calibration curves had good linearity in the concentration ranges 0.2-50 ng/mL for IM, M-2, M-3, M-4, M-6 and M-8 (method 1) and 1-250 ng/mL for M-5 and M-9 (method 2), respectively. The accuracy and precision in the intra-day and inter-day reproducibility tests were within +/-17.0 and 16.1% at the lowest concentrations, and within +/-12.8 and 11.1% at higher concentrations, respectively. Using these analytical methods, excretion profiles of IM and its metabolites in human urine were successfully determined after oral administration of IM at the therapeutic dosage of 0.1 mg.     

Self-assembly and thermal phase transition behavior of unsymmetrical bolaamphiphiles having glucose- and amino-hydrophilic headgroups

The thermal phase transition and self-assembly behaviors in water of the crystalline lamellar films prepared from unsymmetrical bolaamphiphiles, N-(2-aminoethyl)-N'-(beta-d-glucopyranosyl)-alkanediamide [1(n), n = 12, 14, 16, 17, 18, and 20], have been studied using differential scanning calorimetry, polarized light microscopy, variable-temperature (VT) X-ray diffraction (XRD), and VT-IR spectroscopy. The behavior allowed us to classify the bolaamphiphiles into two categories: short chain 1(n) (n = 12, 14, 16, and 17) and long chain 1(n) (n = 18 and 20). On heating, the films of the long chain 1(n) exhibited polymorphism of two crystal phases (Cr1 and Cr2) and one thermotropic mesophase (smectic). These phases proved to consist of unsymmetrical monolayer lipid membranes (MLMs), in which the molecules packed in a parallel fashion. On the other hand, the films of the short chain 1(n) gave a single crystal phase (Cr1) consisting of symmetrical MLMs with antiparallel molecular packing. Scanning transmission electron microscopy and atomic force microscopy revealed that the long chain 1(n) self-assembles in alkaline aqueous solutions to form nanotubes with 110-120 nm outer diameters, while the short chain 1(n) produces nanotapes with 80-250 nm widths. XRD and IR measurements revealed that the nanotubes consist of unsymmetrical MLMs, while the nanotapes consist of symmetrical MLMs. The molecular packing of the initial solid phase was essentially maintained even in the self-assemblies in water. The self-assembly process in water allowed the symmetrical MLM films of the short chain 1(n) to convert into the symmetrical MLM nanotapes. Similarly, the unsymmetrical MLM films of the long chain 1(n) were converted into the unsymmetrical MLM nanotubes.