Molecular structure of polymerization product containing phenyl- and diphenylsiloxy units

The molecular structure of the hydrolyzate, and of the prepolymers and polymerization products of phenyltrichlorosilane and diphenyldichlorosilane are investigated. ²⁹Si-NMR measurements reveal the kinds of component units and their ratio in each synthesis step. The molecular structure of the prepolymer chain end and the polymerization product are also discussed in relation to the change in the NMR spectra. © 1995 John Wiley & Sons, Inc.     

Teurilene and thyrsiferyl 23-acetate, meso and remarkably cytotoxic compounds from the marine red alga laurencia obtusa (hudson) lamouroux

Two new cyclic ethers consisting of squalene carbon skeleton have been isolated from the red alga L. obtusa. The absolute stereostructure of teurilene ($\text{1}$) was elucidated by x-ray crystallographic method, and the structure of thyrsiferyl 23-acetate ($\text{2}$) was established from the spectral and chemical evidence.     

Decomposition of N2O on Rh-loaded zeolites

N₂O was decomposed over Rh supported on NaY zeolite and ZSM5. With low Rh-loading (≤0.1 wt.%) the activity of Rh was much higher than that supported on SiO₂ and CeO₂. On the contrary, the activity of Rh-loaded zeolites (0.1 wt.%) was not so high or even lower than that on SiO₂ for the oxidation of toluene, which has a larger molecular size than N₂O. Thus the Rh present inside the zeolite cavity was especially effective in the decomposition of N₂O.     

Di-tert-butylsilylene (DTBS) group-directed α-selective galactosylation unaffected by C-2 participating functionalities

We have discovered an unusual α-galactosylation using phenylthioglycoside of 4,6-O-di-tert-butylsilylene (DTBS)-protected galactose derivatives as a glycosyl donor, which was not hampered by the neighboring participation of C-2 acyl functionality such as NTroc and OBz. The power of the DTBS effect has been exemplified by the coupling reaction with various glycosyl acceptors.     

Further studies on reductive metabolism of acetohexamide in heart

Species and sex differences of acetohexamide reductase activity were investigated using the cytosolic fraction of heart homogenate. The activity in the rabbit was considerably higher than that in the other species (guinea pig, hamster, rat and mouse). No sex difference of the activity was observed in any of the species tested. Ketone-containing drugs (daunorubicin, befunolol and levobunolol) other than acetohexamide were little reduced in the cytosol of rabbit heart. Some aldehyde reductase inhibitors (phenobarbital, valproate and chlorothiazide) were found to decrease the acetohexamide reductase activity in the cytosol of rabbit heart.     

Structural studies of a protein using the assigned back-bone carbonyl carbon-13 NMR resonances

Several new methods to observe and assign the back-bone peptide carbonyl carbon NMR resonances of a protein have been developed and applied for Streptomyces subtilisin inhibitor. With the assigned carbonyl resonances various site-specific structural information can be obtained for virtually any site of the peptide chain. By putting those site-specific NMR parameters, including chemical shifts, rotational structures around peptide bond, and solvent accessibilities, together a new algorithm to predict the protein structures in solution has emerged.     

Effects of carboxyl groups on the adsorption behavior of low-molecular-weight substances on a stainless steel surface

The adsorption isotherms of various carboxylic acids and several amines on a stainless steel surface were taken as a function of pH and the ionic strength of the solution at 30 degrees C. In particular, the effect of the number of carboxyl groups on the adsorption behavior was investigated. Monocarboxylic acids such as benzoic acid and n-butyric acid were reversibly adsorbed on the stainless steel particles and showed a Langmuir-type adsorption isotherm, i.e., Q=KqmC/(1+KC), where Q and C are, respectively, the amount of adsorbate adsorbed and the equilibrium concentration in the bulk solution, qm, the maximum adsorbed amount, and K is the adsorption equilibrium constant. Carboxylic acids having plural carboxyl groups had much higher affinity to the surface and were adsorbed in both reversible and irreversible modes. The adsorption isotherms for the carboxylic acids having plural carboxyl groups could be expressed by a modified Langmuir-type adsorption isotherm, i.e., Q=q(irrev)+Kq(rev)C/(1+KC), where q(irrev) and q(rev) are, respectively, the maximum amounts adsorbed irreversibly and reversibly. The K and q(irrev) values increased with an increase in the number of carboxyl groups except for isophthalic acid and terephthalic acid. On the basis of the pH dependencies of K, qm, q(irrev), and q(rev) as well as the surface properties of the stainless steel, both reversible and irreversible adsorptions were considered to occur through the electrostatic interaction between negatively charged carboxyl groups and the positively charged sites on the surface. The dependency of the q(irrev) value on ionic strength was discussed on the basis of the differences in their adsorbed state with the interaction forces to the surface and repulsive forces among the adsorbed molecules. The adsorption of amine components was quite weak. The RA-IR and molecular dynamics calculation were done to investigate the adsorption states of phthalic acid, trimellitic acid, and mellitic acid.     

Reduction behavior of Ru/CeO2 catalysts and their activity for wet oxidation

Three kinds of Ru/CeO₂ catalysts were prepared. The mobility of the oxygen on Ru and their catalytic activity in the wet oxidation of acetic acid was investigated. Ru was present in the form of RuO₂, and TPR experiment showed that the reaction, RuO₂ + 2H₂ Ru + 2H₂O, took place in different temperature ranges depending upon the kind of the catalysts. The catalyst with easily reducible oxygen on Ru had high activity in wet oxidation, and the importance of the release of oxygen from Ru to the reactant was suggested.     

Laurallene,new bromoallene from the marine red alga Laurencia nipponica Yamada

Laurallene ($\text{1}$), a new brominated cyclic ether having a terminal allene moiety, has been isolated as a main constituent from the marine red alga $\text{Laurencia nipponica}$ Yamada (Rhodomelaceae, Rhodophyta) and its structure was determined by its physical and chemical properties.     

Copolymerization of ethylene sulfide and carbon disulfide

Ethylene sulfide was found to copolymerize with carbon disulfide to give poly(ethylene trithiocarbonate) in the presence of Hg(SC₄H₉)₂, Zn(C₂H₅)₂, or Cd(C₂H₅)₂, which are well known as the effective catalysts for the coordinated anionic copolymerization of episulfides. The structure and the composition of the copolymer was determined by the infrared and NMR spectra. To establishe the mechanism of the copolymerization, the reaction of carbon disulfide and Hg(SC₄H₉)₂, and also the ring-opening polymerization of ethylene trithiocarbonate were examined. Carbon disulfide was found to insert easily into the metal-sulfur bond of Hg(SC₄H₉)₂ under the experimental conditions of the copolymerization. On the other hand, the ring-opening polymerization of ethylene trithiocarbonate did not take place with these catalysts, occurring only with the use of sulfuric acid. From these results, the mechanism of the copolymerization was discussed.