Depolymerization of cellouronic acid during TEMPO-mediated oxidation

The mechanism of partial depolymerization of cellouronic acid (-1,4-linked polyglucuronic acid sodium salt) during 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation of cellulose was studied by treating cellouronic acid with one reagent or a combination of TEMPO-NaBr-NaClO under various conditions. Although NaClO, NaBrO and an alkali at pH 11 brought about partial depolymerization of cellouronic acid, the use of these reagents themselves did not seem to be the primary reason for depolymerization. On the other hand, when all the reagents, i.e. TEMPO-NaBr-NaClO, were applied to cellouronic acid at pH 11, a remarkable decrease in weight-average degree of polymerization (DPw) from 430 to ca. 20 was observed within the initial 10 min. Probably hydroxyl radicals formed from NaBrO and TEMPO at pH 10–11 cause the depolymerization during the oxidation. Some radical scavengers were then used for the TEMPO-mediated oxidation of cellulose in order to suppress the depolymerization. Although the addition of crotonic acid under certain conditions gave cellouronic acid having higher DPw, none of the radical scavengers examined so far could completely prevent the depolymerization. When regenerated celluloses having higher DP were used as the starting materials, cellouronic acids having DPw of more than 1000 were obtained, although they still had large low-molecular-weight fractions.     

X-ray studies on layer structure and bistability in ferroelectric liquid crystals

X-ray diffraction measurements of thin chiral smectic C (S_c*) liquid crystals between solid plates coated with rubbed polymer film were performed under an electric field. A variety of local layer structures which depend upon the boundary conditions could be observed, including bookshelf and chevron, and some distorted structures. Moreover, the method of layer deformation could be seen in a stepwise induced field, and seven deformation types could be detected. The relation between a bistability effect and the type of layer deformation was clarified and four deformation types were found favourable to bistability. A vertical layer structure at the boundary, like the bookshelf structure, was necessary to produce bistability. A high pretilt film seemed to have a smectic layer reform a tilted structure even under an induced field and it was difficult to produce bistability with the high pretilt one.     

Structure of β-amino acids in antibiotics iturin A

An antibiotic iturin A was separated into several components (A-1≈8) using HPLC and the structures of the β-amino acids of each component were established based on NMR and mass spectral analysis.     

Preparation of new nitrogen-bridged heterocycles. 59. Syntheses and intramolecular interactions of 3-(acylmethylthio)- and 3-[(3-ethoxycarbonyl-2-propenyl)thio]thieno[3,4-b]indolizine derivatives

Various thieno[3,4-b]indolizine derivatives having an acylmethylthio or (3-ethoxycarbonyl-2-propenyl)thio group at the 3-position which could not be obtained by a conventional method were prepared by a new procedure using cyanoethyl group as a protecting group and their intramolecular arene-pi interactions were investigated. In the (1)H-NMR spectra of these thieno[3,4-b]indolizines, the low-field shifts (delta 0.10-0.33 ppm) for the 5-protons were observed in comparison with those of 3-(methylthio)thieno[3,4-b]indolizines as a standard. The UV spectra also exhibited a characteristic absorption band at 425-445 nm attributable to the arene-pi interaction but their intensities were generally lower than those of 3-(arylmethylthio)thieno[3,4-b]indolizines. In their X-ray analyses, the anti conformation for 3-(acylmethylthio)thieno[3,4-b]indolizines and the gauche one for the 3-(3-ethoxycarbonyl-2-propenyl)thio derivatives were exhibited.     

Preparation and Free-Radical Polymerizations of Methyl-4-vinylphenylsulfoxide and Methyl-4-vinylbenzylsulfoxide

Methyl-4-vinylphenylsulfoxide (1) was prepared by the selective oxidation of 4-methylthiostyrene with sodium metaperiodate in 87% yield. This monomer was readily homopolymerized in DMSO by AIBN at 60°C. The polymer obtained is soluble in ethanol, chloroform, DMSO, and DMF, but insoluble in water, benzene, and petroleum ether. The inherent viscosity of this polymer was 0.33 dL/g in DMSO. This sulfoxide monomer (1) was copolymerized with styrene, methyl methacrylate, acrylo-nitrile, and acrylamide under radical conditions. From the copolymerization with styrene, copolymerization parameters were obtained as follows; r¹ = 0.56, r_St, = 0.26, and Q¹ = 1.19, e¹ = 0.58. Similarly, methyl-4-vinylbenzylsulfoxide (2) was prepared, and the polymerizability of (2) was also investigated.     

Supported Noble Metal Catalysts and Adsorbents with Soft Lewis Acid Functions

Heterogeneous noble metal catalysts exhibit various functions. Although their redox functions have been extensively studied, we focused on their soft Lewis acid functions. Supported Au, Pt, and Pd catalysts electrophilically attack the π-electrons of soft bases such as alkynes, alkenes, and aromatic compounds to perform addition and substitution reactions. Hydroamination, intramolecular cyclization of alkynyl carboxylic acids, isomerization of allylic esters, vinyl exchange reactions, Wacker oxidation, and oxidative homocoupling of aromatics are introduced based on a discussion of the active species and reaction mechanisms. Furthermore, the adsorption of sulfur compounds, which are soft bases, onto the supported AuNPs is discussed. The adsorption and removal of 1,3-dimethyltrisulfane (DMTS), which is the compound responsible for the stale odor of “hine-ka” in alcoholic beverages, particularly Japanese sake, is described.