5-Fluorouracil derivatives. Vii. Tert-amine promoted n-glycosidation of pyrimidines

Acylglycosyl halides react smoothly with N₁ - and N₃-(octylthio)-carbonylpyrimidines in the presence of tert-amine to give the corresponding nucleosides in good yields.     

Chemical modification of the reducing chain end in dextrans and trimethylsilylation of its hydroxyl groups

The reducing ends of dextrans, of which number-average molecular weights were 3600 and 16000, were almost quantitatively converted to lactone, amine, and acyllactam groups, successively, by iodine oxidation followed by lactonization, aminolysis with 1,4-diaminobutane, and finally reaction with terephthaloylbis (?-caprolactam). Hydroxyl groups in dextrans were also trimethylsilylated for protection with a mixture of 1,1,1,3,3,3-hexamethyldisilazane and trimethylchlorosilane. In advance of every run, the adequate reaction conditions were search by using D -maltose as a low molecular weight model compound for dextrans.     

Photodimerization of 1,4-dicinnamoylbenzene crystal via a topochemical process

1,4-Dicinnamoylbenzene crystals photodimerize readily via a double [2+2] cycloaddition into the corresponding tricyclic dimer, which consists of two cyclobutane rings and a macro ring bridged by two phenylene linkages.     

Heat capacity of water in poly(methyl methacrylate) hydrogel membrane for an artificial kidney

The heat capacities of a poly(methyl methacrylate) hydrogel membrane for an artificial kidney have been determined over the range of temperatures from 228 to 298 K as a function of water content. At least two kinds of water were found: freezable water and nonfreezable water. The partial specific heat capacities of both waters were calculated from the dependence of heat capacity of the hydrogel on the water content. The heat capacities of freezable water were estimated to be 1.04 cal g⁻¹ K⁻¹ at 298 K and 0.47 cal g⁻¹ K⁻¹ at 228 K. The mobility must therefore be similar to that of bulk water at 298 K, though the melting temperature was lower than that of bulk water. Consequently, the freezable water was not assigned to bound water but to pore water for which the melting temperature was depressed due to interfacial tension. On the other hand, the heat capacities of nonfreezable water were estimated to be 1.02 cal g⁻¹ K⁻¹ at 298 K and 1.06 cal g⁻¹ K⁻¹ at 228 K. The mobility of the water would be similar to that of free water at both 298 and 228 K. © 1995 John Wiley & Sons, Inc.     

Direct writing of Ag-lines on Mn-Zn ferrite by laser-induced thermal decomposition by CH3COOAg

Laser-induced direct writing of silver lines on a ferrite surface from a silver acetate (CH₃COOAg) thin layer has been investigated. The deposition is a thermochemical process and the threshold temperature for thermal decomposition of CH₃COOAg is about 380° C. About 100% of Ag in the deposited lines has been achieved. The width of the deposited Ag-lines increased with the increase in laser power, and it can be accurately estimated by the temperature profile induced by laser irradiation within the power region below the melting point of ferrite. A line thickness of micron order can be formed both on a ferrite surface and on a deposited SiO₂ surface, whereas the line width decreased with the increase in beam dwell time due to the vaporization of both CH₃COOAg precursor and deposited Ag material.On leave from D. S. Scanner Co., Ltd., 5-3-7, Fukushima, Osaka 553, JapanOn leave from Sensor Device Laboratory, Central Research Institute, Glory Co. Ltd., Hyogo 670, Japan     

Determination of acidic saponins in crude drugs by high- performance liquid chromatography on octadecylsilyl porous glass

High-performance liquid chromatographic (HPLC) analysis on octadecylsilyl porous glass was investigated for acidic saponins in ginseng, bupleurum root and senega. The acidic saponins, malonyl-ginsenosides, malonyl-saikosaponins and senegins, as well as neutral saponins in the crude drugs were separated rapidly by HPLC on this column with aqueous acetonitrile containing KH₂ PO₄ as the mobile phase at room temperature.     

Preparation of monodisperse hydrophilic polyamide by anionic polymerization of bicyclic oxalactam

The preparation of a monodisperse hydrophilic polyamide was achieved in the anionic polymerization of a bicyclic oxalactam, 8-oxa-6-azabicyclo[3.2.1]octan-7-one (abbreviated BOL) with the use of N-benzoyl BOL and potassium pyrrolidonate (2 and 0.5 mol % to BOL, respectively) in dimethyl sulfoxide at 25°C. The number-average molecular weight of the polyamide increased in direct proportion to the monomer conversion, and was consistent with the value calculated from the amounts of the consumed monomer and activator. The molecular weight distribution (MWD) of the polyamide obtained until the middle stage of polymerization (polymerization time, < 10 min; monomer conversion, < 60%) was found to be narrow (M_w/M_n = 1.1). The MWD was gradually broadened in the later stage of the polymerization, which may result from the redistribution of molecular weight of the resulting polyamide not only by the polymerization–depolymerization equilibrium, but also by transamidation between polymer chains.     

Microwave spectra of deuterated ethylenes: Dipole moment and rz structure

The pure rotational spectra of three deuterated ethylenes, CH₂CD₂, CH₂CHD, and cis-CHDCHD, were observed by microwave spectroscopy, and the rotational and centrifugal distortion constants were determined precisely. The dipole moment of CH₂CD₂ was calculated from the Stark effects to be 0.0091 ± 0.0004 D. From the observed rotational constants the average structure was calculated to be $\text{r}{}_{\mathrm{z}}\text{(CC)}\text{= 1.3391 ± 0.0013}\text{A}\text{?}$, $\text{r}{}_{\mathrm{z}}\text{(CH)}\text{= 1.0869 ± 0.0013}\text{A}\text{?}$, θ_z(CCH) = 121.28 ± 0.10°, and $\text{r}{}_{\mathrm{z}}\text{(CH)}\text{- r}{}_{\mathrm{z}}\text{(CD)}\text{= 0.00137 ± 0.00037}\text{A}\text{?}$, where the errors include one standard deviation in the fitting and errors due to an uncertainty (±0.03°) in θ_z(CCH) - θ_z(CCD).