Simultaneous ultramicrodetermination of heterogeneous halogens in organic compounds

The simultaneous ultramicrodetermination of heterogeneous halogens in organic compounds was carried out by the potentiometric titration with 0.002 M silver nitrate after the sample was decomposed by the flask combustion method. In examination of the titration, it was found that clear potential break at the end point was obtained by controlling the delivery speed of the titrant at 0.2 ml/min or slower and the temperature of the solution to be titrated at ca. 10 °C when chloride ion is present. The error due to coprecipitation during the titration and the effect of the mole ratio of heterogeneous halide ions in the sample solution was examined and discussed. The analysis of organic halogen compounds resulted in an error of within 0.4% and standard deviation of less than 0.25%.     

A novel ring transformation of uracil into the benzene ring system

Reaction of 5-formyl-1,3-dimethyluracil with some active methylene compounds in the presence of base causes novel ring transformations to give the p-hydroxybenzoates and the nicotinate.     

A new selective population transfer experiment using a double pulsed field gradient spin-echo

A new pulse sequence is proposed for the determination of scalar coupling correlation in small- and medium-sized organic compounds. The method uses a combination of the double pulsed field gradient spin-echo (DPFGSE) and the selective population transfer (SPT) techniques and is shown to be useful in the analysis of complex spectra with many overlapped signals. The usefulness of this method in the structural elucidation of natural substances is demonstrated using strychnine and digitoxin as examples.     

A versatile method for preparation of O-alkylperoxycarbonic acids: epoxidation with alkyloxycarbonylimidazoles and hydrogen peroxide

A variety of O-alkylperoxycarbonic acids ($\text{2}$) were conveniently prepared $\text{in}$$\text{situ}$ by utilizing alkyloxycarbonylimidazoles ($\text{1}$) as their precursors. Epoxidation of alkenes with such peroxy-acids was studied and their reactivities were compared with those of peroxycarboxylic acids.     

Synthesis and antiulcer activity of optical isomers of 2-(4-chlorobenzoylamino)-3-[2(1H)-quinolinon-4-yl]propionic acid (rebamipide).

The enantiomers of 2-(4-chlorobenzoylamino)-3-[2(1H)-quinolinon-4-yl] propionic acid [(+/-)-1, rebamipide, OPC-12759], a new antiulcer agent that enhances mucosal resistance, were synthesized from optically active alpha-amino acid derivatives of 2(1H)-quinolinone. The key intermediates, alpha-amino acid derivatives, were prepared by asymmetric synthesis and optical resolution. The (+)-1 was about 1.7 times as potent as the (-)-isomer in antiulcer activity against ethanol-induced gastric ulcers.     

Effects of metal salts on polymerization. Part VII. Radical polymerization and spectra of vinylpyridine in the presence of cobaltous chloride

The radical polymerizability of vinylpyridines in the presence of cobaltous chloride was studied in DMF solution, and the results were correlated with the spectroscopic data obtained for methanol solution. In general, the behavior of vinylpyridine complexed with cobaltous chloride is qualitatively the same as that of zinc complexes reported previously. The rates of polymerization were enhanced by the addition of cobaltous chloride when 4-vinylpyridine(4-VP) or 2-methyl-5-vinylpyridine(MVP) was the monomer, whereas the polymerization of 2-vinylpyridine(2-VP) was retarded by cobaltous chloride. The monomer reactivity of all the vinylpyridines was also enhanced by complex formation as studied by copolymerization with styrene. The enhancement of reactivity of 4-VP complexed with cobaltous chloride is somewhat smaller than that of the corresponding zinc complex.     

Molecular mobility of lyophilized poly(vinylpyrrolidone) and methylcellulose as determined by the laboratory and rotating frame spin-lattice relaxation times of 1H and 13C

Laboratory- and rotating- frame spin-lattice relaxation times (T(1) and T(1rho)) of (1)H and (13)C in lyophilized poly(vinylpyrrolidone) (PVP) and methylcellulose (MC) are determined to examine feasibility of using T(1) and T(1rho) as a measure of molecular motions on large time scales related to the storage stability of lyophilized formulations. The T(1rho) of proton and carbon was found to reflect the mobility of PVP and MC backbones, indicating that it is useful as a measure of large-time-scale molecular motions. In contrast to the T(1rho), the T(1) of proton measured in the same temperature range reflected the mobility of PVP and MC side chains. The T(1) of proton may be useful as a measure of local molecular motions on a smaller-time-scale, although the measurement is interfered by moisture under some conditions. The temperature dependence of T(1) and T(1rho) indicated that methylene in the MC molecule had much higher mobility than that in the dextran molecule, also indicated that methylene in the PVP side chain had a higher mobility than that in the MC side chain.