Prospects of Sol-Gel Process for Spectral Hole-Burning Glasses

Persistent spectral hole burning was studied in Eu³⁺ ions-doped Al₂O₃-SiO₂ glass prepared by a sol-gel method. The gel synthesized by the hydrolysis of Si- and Al-alkoxides and EuCl₃·6H₂O was heated in air and hydrogen gas atmospheres. For the glass heated in air to contain OH bonds, the hole was formed by the photoinduced rearrangement of the OH bonds surrounding the Eu³⁺ ions, and was thermally refilled and erased above 200 K. On the other hand, the glass heated in hydrogen gas showed the hole spectrum above 200 K. It was found that the hole depth was independent of the temperature and was 7% of the total intensity at room temperature. The proposed mechanism was the electron transfer between the Eu³⁺ ions and the defect centers formed in glass matrix.     

Lupane-triterpene glycosides from the leaves of Acanthopanax gracilistylus

A novel lupane-triterpene glycoside, called wujiapioside B (1), was isolated from the leaves of Acanthopanax gracilistylus (Araliaceae) together with three known lupane-triterpene glycosides, acankoreoside C (2), acantrifoside A (3) and 3-epibetulinic acid 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester (4). Based on spectroscopic data, the chemical structure of 1 was determined as 3alpha,23-dihydroxy-lup-20(29)-en-28-oic acid 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester. Compounds 2-3 were obtained for the first time from this plant and compound 4 has not been isolated from Acanthopanax genus yet.     

Studies on the syntheses of heterocylic compounds—762: Synthesis of 3-benzyl-6-methyl-2-oxo-3,6-diazabicyclo[3.1.0]hexane as a synthetic intermediate of mitomycins

(±)-1-Benzyl-3α-hydroxy-4β-methylamino-2-oxopyrrolidine (15) and its cis-isomer (16) were synthesised from 1-benzyl-4-ethoxycarbonyl-2,3-dioxopyrrolidine (2) in several steps. The former (15) was converted to 3-benzyl-6-methyl-2-oxo-3,6-diazabicyclo[3.1.0]hexane (17) with a mixture of triphenylphosphine, carbon tetrachloride and triethylamine.     

Synthesis of Six-Membered Compounds by Environmentally Friendly Cyclization Using Indirect Electrolysis

[Ni(cyclam)](ClO(4))(2)-catalyzed indirect electroreduction of olefinic bromides produced six-membered compounds in low to high yields. The synthetic intermediate 49 of Ipecac and Corynanthe alkaloids was obtained in 88% yield in a highly stereoselective manner. Lactam 66, the synthetic precursor of tacamonine, was prepared in 49% yield as a mixture of two diastereoisomers. The electrolysis of the bromoacetates gave the debrominated compounds in good yields.     

Volumetric study on the inclusion complex formation of α- and β-cyclodextrin with 1-alkanols at different temperatures

The partial molar volumes (V_a) of 1-alkanols (carbon number, m=5, 6, 7) in - and -cyclodextrin (CD) solutions at 5.00 mmol kg^–1 have been determined as a function of alkanol concentration (C_a) between 293.2 and 308.2 K by using a dilatometer. It has been observed that with an increase in C_a, V_a increased in -CD solution but decreased in -CD solution, asymptotically to a value of V_a in CD-free water. The dependence of V_a on C_a provided the binding constant (K) of 1:1 complex, the volume change in complex formation, and the partial molar volume of complex itself. The complex formation mechanism has been discussed on the basis of these values and their carbon number dependences in the respect of geometric behavior, hydrophobic interaction, and van der Waals interaction. It is concluded that the CD cavity in water is not rigid but flexible for fitting in nicely with guest molecule.     

Two novel dicoumaro-p-menthanes from Gerbera piloselloides (L.) CASS

Two new type dicoumarins (dicoumaro-p-menthanes), named dibothrioclinins I (1) and II (2) were isolated from the roots and rhizomes of Gerbera piloselloides (L.) CASS., collected in Yunnan Province, China. Their structures were elucidated on the basis of MS, 1D ((1)H-NMR, (13)C-NMR, DEPT and NOE) and 2D ((1)H-(1)H COSY, HMQC, HMBC) NMR spectral analyses. The relative structures of the two compounds were established by NOE difference spectroscopy and further confirmed by single-crystal X-ray diffraction studies.     

Hydrogen Gas Sensing of High Electrical Conducting-P2O5-SiO2 Glasses Prepared by Sol-Gel Process

High proton-conducting P₂O₅-SiO₂ glass was applied to the electrolyte of the hydrogen concentration cell for hydrogen gas sensing. 5P₂O₅·95SiO₂ glass was prepared using the sol-gel method and its electrical conductivity and electromotive force were measured at 50°C as a function of both the ambient humidity and hydrogen gas concentration. The electrical conductivities increased with increasing humidity and reached 10^–2 S/cm at 90% relative humidity. The electromotive force of the hydrogen concentration cell, where the glass was used as a membrane, showed good Nernstian response to hydrogen pressure in the high relative humidity region.     

Some aspects of plasma copolymerization of acetylene with N2 and/or water

Plasma polymerizations of mixture of acetylene-N₂, acetylene-H₂O, were investigated by using an electrodeless glow discharge from a 13.5-MHz radiofrequency source. Properties of plasma polymers were examined as functions of mole ratios of N₂ and/or H₂O to acetylene. The concentration of trapped free radicals and the internal stress in a plasma polymer decreased as the mole ratio of N₂ or H₂O increased. Water showed the most pronounced effects in those properties at the mole ratio of 0.3. Gas permeabilities increased by the copolymerization of N₂ and/or H₂O. Surface energies were also investigated by analysis of contact angles of liquids. Copolymerization of N₂ caused a remarkable increase in polar contribution of surface energy. Some fundamental aspects of flow-rate pressure relationship of mixed gases are presented.