Organometallic compounds : XII. stereochemical interconversion reactions between 1,1′−bis(α-hydroxyalkyl)ferrocenes and 7-oxa[3]ferrocenophanes

Meso and racemic isomers of 1,1′-bis(α-hydroxyalkyl)ferrocene derivatives, and trans and cis isomers of 7-oxa[3]ferrocenophanes have been isolated. The configurations of these isomers have been determined both by spectroscopy and from their reaction behavior. It has been found that the ring-closure and ring-opening interconversion reactions between 1,1′-bis(α-hydroxyalkyl)ferrocenes and 7-oxa[3]ferrocenophanes are stereospecific. PMR spectra of the diols and ethers have been examined at 100 MHz in CF₃COOH, and the existence of α-[1′-(α-hydroxyalkyl)ferrocenyl]carbonium ions has been demonstrated in this acid. A mechanism for the various interconversion reactions is proposed on the basis of their stereospecific reactivity and from the PMR spectra of the carbonium ions.     

Optically active 2-p-tolylsulfinylacrylate a novel chiral dienophile which exhibits high reactivity and diastereoselectivity

The Diels-Alder reaction of a novel chiral dienophile, alkyl ($\text{S}$)-2-$\text{p}$-tolylsulfinylacrylates 1 with anthracene and cyclopentadiene showed high diastereoselectivity under the chelation controlled condition.     

Soluble polymer-supported catalysts containing pendant quaternary onium salts for the addition reaction of oxiranes with carbon dioxide

The addition reaction of oxiranes ( 15a-d ) with carbon dioxide (CO₂) was carried out using 1 mol % of soluble polymer-supported quaternary onium salts as catalysts under atmospheric pressure. The reaction of 15a-d with CO₂ proceeded very smoothly to give the corresponding five-membered cyclic carbonates ( 16a-d ) in high yields at 90-100°C. The catalytic activity of the soluble polymer-supported quaternary onium salts was strongly affected by the following factors: kind of reaction solvent, degree of introduction of the pendant onium salt residues in the polymer chain, and type of alkyl group on the onium salts due to the balance between lipophilicity and steric hindrance of the onium salt residue. Furthermore, these soluble polymer-supported quaternary onium salts were found ordinarily to have higher catalytic activity than low molecular weight quaternary onium salts under the same reaction conditions. It was also found that the rate of reaction was proportional both to catalyst concentration and to oxirane concentration. © 1995 John Wiley & Sons, Inc.     

Electrochemical characterization of negative electrodes consisting of surface-modified Zr0.9Ti0.1(Ni1.1Co0.1Mn0.5V0.2Cr0.1)x Laves-phase alloys

Laves-phase hydrogen storage alloy has a high potential for use as negative electrode material as alternative for the misch-metal-based material. In order to improve the energy density and the rate capability of negative electrode, chemical and mechanical modification of Lavesphase alloy with different stoichiometric ratios was carried out. Discharge capacity and high-rate dischargeabilty was evaluated by electrochemical methods and the characterization of Laves-phase alloy was made by X-ray diffraction, SEM observation and PCT measurement. The best result in discharge capacity could be obtained for stoichiometric Laves-phase alloy with a composition of Zr_0.9Ti_0.1Ni_1.1Co_0.1Mn_0.5V_0.2Cr_0.1 by boiling in 10 M KOH solution. On the other hand, the high-rate dischargeability was increased remarkably by introducing mechanical grinding before alkali treatment. The cause for improved performance was discussed on the basis of thermodynamic stability of metal hydride and changes in crystal structure and surface morphology influencing on diffusion coefficient and diffusion path length of hydrogen.     

Stereoselective synthesis of 2-methylenepyrrolizidines by tandem cyclization of N-propargylaminyl radicals

Tandem cyclization of N-propargylaminyl radicals, generated by N-chlorination of (E)-alk-4-enylamines 2a-d and 2f followed by treatment with tributyltin radical, afforded 2-methylenepyrrolizidines 3a-d and 3f in a highly stereoselective manner. A similar radical cyclization of (Z)-N-propargyl-1-methyl-5-phenylpent-4-enylamine (2e) gave pyrrolizidine 3b having the same stereochemistry as that obtained from the E isomer 2b.     

Fast separation of oligonucleotide and triplet repeat DNA on a microfabricated capillary electrophoresis device and capillary electrophoresis

A laser-induced fluorescence detection system coupled with a highly sensitive silicon-intensified target (SIT) camera is successfully applied to the imaging of a band for DNA fragment labeling by fluorescence dye in a microchannel, and to the visualizing of the separation process on a microfabricated chip. We demonstrated that an only 6 mm separation channel is sufficient for the separation of triplet repeat DNA fragment and DNA molecular marker within only 12 s. The separation using the microfabricated capillary electrophoresis device is confirmed to be at least 18 times faster than the same separation carried out by conventional capillary electrophoresis with 24.5 cm effective length. The use of a short capillary with 8.5 cm effective length is also efficient for fast separation of DNA; however, the microchip technology is even faster than capillary electrophoresis using a short capillary.     

Novel evaluation method of biodegradabilities for oil-based polycaprolactone by naturally occurring radiocarbon-14 concentration using accelerator mass spectrometry based on ISO 14855-2 in controlled compost

The biodegradabilities of poly(?-caprolactone) (PCL) powders (av. size = 180.7 μm) in controlled compost at 58 °C have been studied using the microbial oxidative degradation analyzer (MODA) based on ISO 14855-2 entitled “Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions - Method by analysis of evolved carbon dioxide - Part 2: Gravimetric measurement of carbon dioxide evolved in a laboratory-scale test”. The biodegradability of the PCL powders was 101.4% in a 56-day test period by the ISO method. The biodegradabilities of PCL powders have been studied using percent modern carbon (pMC) measured by accelerated mass spectrometry (AMS). Trapped CO₂ was analyzed by AMS to determine the pMC (sample) using ¹⁴C radiocarbon concentration. By using the theory that the pMC (sample) was the sum of pMC (compost) (104.88%) and pMC (PCL) (0%) as the respective ratios in the determined period, CO₂ (respiration) was calculated only from one reaction vessel. The biodegradability of PCL powders was 79.9% in a 56-day test period by the AMS method. It was found that respiration activities in the sample vessel including PCL, compost and sea sand were the same as that in the blank vessel including compost and sea sand without PCL during the active biodegradation period (0-33 day) at 58 °C. It was confirmed that respiration activities in the sample vessel were slightly higher than that in the blank vessel after active biodegradation due to the propagation of microorganisms using energy and metabolites by PCL biodegradation during those periods.     

The photochemical isomerization of cross-linked 1,3,5-tristyrylbenzene dendrimer with hula-twist mechanism

A cross-linked 1,3,5-tristyrylbenzene dendrimer 5 was synthesized to study the photochemical isomerization mechanism. On irradiation, 5 isomerized with the quantum yields (Φ_E→Z) of 0.063, which was not very much different from that for a model compound 1 (Φ_E→Z 0.080), supporting a volume-conserving hula-twist (HT) mechanism during the photochemical E-Z isomerization.     

PREPARATION AND PROPERTY OF POLYMERIC PENDANT Ru(bpy)_3~(2+) COMPLEXES

Polymeric pendant Ru(bpy)_3~(2+) complexes were prepared from homopolymer and copolymers of 4-methyl-4'-vinyl-2,2'-bipyridine (Vbpy). Vbpy was prepared from 4-methylpyridine. The comonomers were styrene (St), acrylic acid (AA), N-vinylpyrrolidone (Pyr), 4-vinylpyridine (Vpy), methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), acrylonitrile (AN) and N-ethyl-4-vinylpyridium bromide (EQ-Vpy). The fraction of the pendant Ru(bpy)_3~(2+) repeating unit in the polymeric complex was 0.022 to 0.052. Absorption maximum, molar extinction coefficient, emission maximum and relative emission intensity of the polymeric complexes were studied.     

Characterization of two polysaccharides having activity on the reticuloendothelial system from the root of Glycyrrhiza uralensis

Two polysaccharides, called glycyrrhizans UA and UB, were isolated from the root of Glycyrrhiza uralensis Fischer. They were homogeneous on electrophoresis and gel chromatography, and showed reticuloendothelial system-potentiating activity in a carbon clearance test. Glycyrrhizan UA is composed of L-arabinose: D-galactose: L-rhamnose: D-galacturonic acid in the molar ratio of 20:14:1:3, and glycyrrhizan UB is composed of L-arabinose: D-galactose: D-glucose: L-rhamnose: D-galacturonic acid in the molar ratio of 12:10:1:10:20, in addition to small amounts of O-acetyl groups and peptide moiety, respectively. About 10% (glycyrrhizan UA) and 35% (glycyrrhizan UB) of the D-galacturonic acid residues exist as the methyl esters. Methylation analysis, carbon-13 nuclear magnetic resonance and periodate oxidation studies indicated their structural features.