Intramolecular Diels-Alder Reactions of Thio-Substituted Dienes with Enones

Thio-substituted dienes bearing an enone moiety were readily prepared from 3-sulfolenes, and their intramolecular Diels-Alder (IMDA) reactions were studied. Octahydronaphthalenones were produced in good yield with high stereoselectivity. Hexahydroindenones were also obtained, but the stereoselectivity was lower.     

二氧化硫的电化学氧化过程：Ⅲ.SO2在聚钴卟啉电极上的氧化机理

采用循环伏安法，稳态法，计时电位法等研究了ＳＯ２在聚钴卟啉膜电极上的电化学氧化过程，并和ＳＯ２在贵金属电极上的行为进行了比较。     

Studies on the thermotropic liquid crystalline polymer. XII. Synthesis and properties of crosslinkable thermotropic liquid crystalline homo- and copoly(ether-ester)s

A series of crosslinkable thermotropic liquid crystalline poly(ether-ester)s and copoly(ether-ester)s was prepared. All of the polymers were crosslinked by thermal treatment or photo-irradiation upon heating. The thermal stability and thermal crosslinking reaction of these polymers were investigated. These polymers also could be crosslinked by copolymerization with vinyl monomers, such as styrene or methyl methacrylate. The crosslinked polymers exhibited thermotropic liquid crystalline behavior after softening by heating. The phase behavior of linear polymers and crosslinked polymers was studied by differential scanning calorimetry (DSC) and an optical polarizing microscope equipped with a heating stage. © 1995 John Wiley & Sons, Inc.     

A validated HPLC method with ultraviolet detection for the determination of buformin in plasma

A sensitive and rapid high-performance liquid chromatographic assay is developed and validated for the determination of buformin in plasma. After addition of metformin as the internal standard, the analytes were deproteinated with acetonitrile, washed with dichloromethane, and the resulting supernatant injected. Chromatography was performed at ambient temperature by pumping a mobile phase of 0.03 m diammonium hydrogen phosphate buffer (pH 7, 250 mL) in methanol (750 mL) at a fl ow rate of 1 mL/min through a silica column. Buformin and metformin were detected at 236 nm, and eluted 9.8 and 15.4 min, respectively. No endogenous substances were found to interfere. Calibration curves were linear over the concentration range of 20-2000 ng/mL. The limit of quantitation was 20 ng/mL. The intra- and inter-day relative standard deviation (RSD) was 8.3%, or less, and the accuracy was within 10.1% of the relative error (RE). The method is suitable in pharmacokinetic investigation of buformin.     

The synthesis of anthracyclinones-ii : The synthesis of 7,9-bisdeoxycarminomycinone and -daunomycinone

7,9-Bisdeoxycarminomycinone has been synthesised from 5-hydroxyquinizarin by two annelation routes involving nitronate addition to C-2 and aldol condensation at C-3. 4-Demethoxy-7,9-bisdeoxydaunomycinone has been synthesised efficiently by similar methods.     

Two-frequency two-photon ionization of nascent PO(X2II) from the collision-free IR photolysis of dimethyl methylphosphonate

We report the detection of nascent PO produced via the collision-free IR photolysis of dimethyl methylphosphonate. Absorption throughout the B²Σ⁺ ← X²Π system is followed by excitation using 266 nm radiation, which results in PO⁺ + e. Spectral features due to spin-orbit excitation appear extremely “cold” relative to vibrations and rotations.     

青蒿素及其一类物结构和合成的研究——Ⅸ.全合成青蒿素中若干关键化合物的合成

青蒿素是一个含有过氧基团的新型倍半萜内酯~([1]),它具有突出的抗疟作用~([2])。本文报道     

Multilayer nitroazobenzene films covalently attached to carbon. An AFM and electrochemical study

Nitroazobenzene films have been grafted to pyrolyzed photoresist films by electrochemical reduction of the corresponding diazonium salt in acetonitrile solution. Two component films were also prepared by electrochemically grafting methylbenzene layers to preformed NAB films. Voltammetric investigation of the films in aqueous acid medium and the measurement of film thickness using atomic force microscopy (AFM) lead to new insights into film structure. In aqueous acid solution, the azobenzene groups have no detectable electroactivity and not all nitro groups in the films can be reduced. These findings point to a compact film structure in which proton diffusion is limited. There may also be spatial inhibition of the conformational changes that accompany azobenzene reduction. For increasingly thick NAB films, the peak for reduction of the nitro groups moves to more negative potentials and the peaks become more asymmetric in shape. These changes are interpreted in terms of the dielectric properties and the rate of proton diffusion in the films. Film thickness was measured by ploughing through the film with an AFM tip. When an NAB film prepared in acetonitrile solution is reduced in aqueous acid, the film thickness decreases by more than 50%. The changes can be partially reversed by treatment in acetonitrile-electrolyte solution and hence are attributed to ion-solvent induced swelling and shrinking. Thus, the large decrease in thickness detected by AFM after treatment of the film in aqueous acid is consistent with the compact film structure revealed by electrochemistry.     

Immobilization of a Monolayer of Bovine Serum Albumin on Gold Nanoparticles for Stereo‐specified Recognition of Dansyl‐norvaline

The assembly strategy to prepare a monolayer of bovine serum albumin on the surface of silica gel supported gold nanoparticles is described. The stereo‐specific recognition ability of this material was evaluated by enantioresolution of Dansyl‐norvaline. For enantiomeric separation, the influences of buffer concentration and the concentration of organic modifier on the separation performance were investigated. A better separation in terms of enantioresolution and peak shape was found with the phosphate concentration at 30 mM. Moreover, the peak shape and resolution can be improved by the addition of methanol solution. Enantioresolution of Dansyl‐norvaline was obtained from this material at optimized conditions. It appears that the immobilization of a monolayer of bovine serum albumin on gold nanoparticles as the chiral selector of Dansyl‐derivative amino acid is promising.