Asymmetric synthesis of abietane diterpenoids via B-alkyl Suzuki-Miyaura coupling. Formal total asymmetric synthesis of 12-deoxyroyleanone and cryptoquinone

A convergent synthetic strategy for abietane diterpenoids via B-alkyl Suzuki-Miyaura coupling and Lewis acid-mediated cyclization reactions is established. Asymmetric total synthesis of 12-deoxyroyleanone, an antileishmanial diterpene, is described.     

Reactions between ammonium sulphate and metal oxides (metal=Cr,Mn and Fe) and thermal decomposition of the products

The reactions between ammonium sulphate and three metal oxides (Cr₂O₃, MnO₂ and Fe₂O₃) were studied. It was confirmed by X-ray diffraction and chemical analysis that stable reaction intermediates were formed consecutively in the course of the reactions.These were (NH₄)₃M(SO₄)₃ and NH₄M(SO₄)₂ for Cr₂O₃ and Fe₂O₃ and (NH₄)₂Mn₂(SO₄)₃ for MnO₂. The thermal decompositions of these intermediates and of the metal sulphates were carried out. The contracting-volume equation was valid for the decomposition of all the intermediates. The Arrhenius parameters were determined.

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Zusammenfassung Es wurden die Reaktionen zwischen Ammoniumsulfat und drei Metalloxiden (Cr₂O₃, MnO₂ und Fe₂O₃) untersucht. Durch Röntgendiffraktion und chemische Analyse wurde bestätigt, dass im Verlaufe der Reaktion stabile Zwischenprodukte gebildet werden. Es handelt sich dabei um (NH₄)₃M(SO₄)₃ und NH₄M(SO₄)₂ im Falle von Cr₂O₃ und Fe₂O₃ und um (NH₄)₂Mn₂(SO₄)₃ im Falle von MnO₂. Diese Zwischenprodukte und die Metallsulfate wurden thermisch zersetzt. Die Volumenkontraktionsgleichung war für die Zersetzung all dieser Zwischenprodukte gültig. Die Arrheniusparameter wurden bestimmt.

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Cr₂O₃, MnO₂ Fe₂O₃. , . , (NH₄)₃M(SO₄)₃ NH₄M(SO₄)₂, (NH₄)₂Mn₂(SO₄)₃. . . .

     

A new method for the synthesis of some 9-β-D-arabinofuranosylpurines by a combination of chemical and enzymatic reactions

An enzymatic transarabinosylation between 2-chlorohypoxanthine and 1-β-$\text{D}$-arabinofuranosyluracil gave 9-β-$\text{D}$-arabinofuranosyl-2-chlorohypoxanthine which was chemically converted to 9-β-$\text{D}$-arabinofuranosylguanine and its derivatives.     

Improving the properties of the proton exchange membranes by introducing α-methylstyrene in the pre-irradiation induced graft polymerization

New proton exchange membranes (PEMs) were prepared by pre-irradiation induced grafting of α-methylstyrene (AMS)/styrene (STY)/divinylbenzene (DVB) into the crosslinked polytetrafluoroethylene (RX-PTFE) films and successively sulfonated. The new PEMs showed the improved glass transition temperature and chemical stability as compared with the PEMs prepared by pre-irradiation induced grafting of STY/DVB. The balance of the cost, grafting kinetic, thermal properties and the properties of the resulted proton exchange membrane is the key point of this work.     

Synthesis of inorganic-organic hybrids by incorporation of inorganic components into organic polymer using metal alkoxides

Inorganic-organic hybrids have been synthesized by incorporation of the inorganic component of Ti(OC₂H₅)₄ into the organic polymer of ethyl cellulose. The inorganic-organic hybrids did not dissolve in toluene used as a solvent for the starting materials. The ethanol was formed as a by-product of the alcoholysis condensation reaction between Ti(OC₂H₅)₄ and ethyl cellulose. These results suggest that ethoxy groups of Ti(OC₂H₅)₄ react with hydroxy groups of ethyl cellulose to form cross-linking bonds of –O–Ti–O–. The reaction of Ti(OC₂H₅)₄ with ethyl cellulose was further investigated by Fourier transform infrared (FT-IR) spectroscopy. The FT-IR spectroscopic experiments revealed that the Ti–O bond state of Ti(OC₂H₅)₄ was changed by refluxing a toluene solution of Ti(OC₂H₅)₄ with ethyl cellulose. The inorganic-organic hybrids have an interesting dielectric property; their dielectric constant is higher than that of ethyl cellulose and that of a simple mixture of TiO₂ and ethyl cellulose.     

Effect of urea addition on chiral separation of dansylamino acids by capillary zone electrophoresis with cyclodextrins

The chiral separation ability of unmodified and di- and trimethylated -, β- and γ-cyclodextrins (CDs) as chiral selectors in capillary zone electrophoresis was investigated in the presence of urea derivatives using twelve dansylamino acids as model solutes. The addition of these urea derivatives (unsubstituted, methyl-, ethyl- and 1,3-dimethylureas) produced dramatic enhancement in the enantioselectivity of unmodified β-CD but also reduced the enantioselectivities of the other CDs.     

Template-directed DNA photoligation via alpha-5-cyanovinyldeoxyuridine

[reaction: see text] We describe an efficient template-directed photoligation of oligodeoxynucleotides (ODNs) using alpha-5-cyanovinyldeoxyuridine (alpha(C)U). An efficient photoligation was produced by photoirradiation of an ODN containing alpha(C)U at the 3' end with an ODN containing thymine at the 5' end in the presence of a template ODN. This photoligation method is a new and efficient way to synthesize branched ODNs.     

Characterization of phase transition of Ba2-xSrxIn2O5 by thermal analysis and high temperature X-ray diffraction

The phase transitions of Ba_2-xSr_xIn₂O₅ were investigated with various thermal analyses and high-temperature X-ray diffraction. It was clarified that crystal structure of Ba_2-xSr_xIn₂O₅ with x=0.0~0.4 varies from brownmillerite through distorted perovskite to another distorted perovskite with increase of temperature. The phase transition from brownmillerite to distorted perovskite was revealed to be first order, whereas transition from distorted perovskite to another one was second order. The specimen with x≥0.5 showed only one first order phase transition from brownmillerite to distorted perovskite. The phase diagram of Ba_2-xSr_xIn₂O₅ was established and existence of tricritical point at ~1100°C with x=0.4~0.5 was suggested. This revised version was published online in August 2006 with corrections to the Cover Date.     

Uneven distribution of ventilation—perfusion ratios in lungs estimated by a modified Newton method

The uneven distribution of ventilation—perfusion ratios ( ) in diseased lungs is the major cause of arterial hypoxemia. Farhi and Yokoyama (1967) and Yokoyama and Farhi (1967) were the first who used physiologically inert gases as indicator gases to assess the uneven distribution of Wagner and his coworkers in San Diego (1977b) extended the method and elaborated the multiple inert gas elimination technique in which blood flows in 50 compartments with different were estimated based on data for 6 indicator gases. They analyzed the indicator gas data through an enforced smoothing technique with the ridge regression. To get smooth distributions, they introduced a weighting function for compartments and an additional treatment for the non-negativity of the blood flow. The weighting function was empirically obtained. We analyzed the data without putting any weights on compartments nor any additional treatment for non-negativity of blood flow. The analytical method in the present study was a modified Newton method, which is one of the enforced smoothing method. Our method was capable of recovering all distribution patterns that were found through the method reported by Wagner et al. (1977b).