Asymmetric hydrogenation of alpha-chloro aromatic ketones catalyzed by eta6-arene/TsDPEN-ruthenium(II) complexes

Asymmetric hydrogenation of various alpha-chloro aromatic ketones with Ru(OTf)(TsDPEN)(eta6-arene) (TsDPEN = N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine) produces the chiral chlorohydrins in up to 98% ee. This reaction can be conducted even on a 206-g scale. The hydrogenation of an alpha-chloro ketone with a phenol moiety has been utilized for the synthesis of (R)-norphenylephrine without protection-deprotection operations. [reaction: see text].     

Laccase-catalyzed conversion of green tea catechins in the presence of gallic acid to epitheaflagallin and epitheaflagallin 3-O-gallate

Green tea extract containing catechin mixtures was treated with gallic acid using laccase (EC 1.10.3.2) to improve its function as a food material. After enzymatic oxidation, two new products were detected on an HPLC chromatogram. These products were purified by extraction with ethyl acetate, sequential column chromatographies, and crystallization. On the basis of ¹H/¹³C NMR, MALDI-TOF/high resolution MS, and UV-visible absorption spectral analyses, they were confirmed to be epitheaflagallin (5) and epitheaflagallin 3-O-gallate (6). This enzymatic process allows us to preferentially convert catechin derivatives in a crude mixture of green tea into different compounds.     

Dirhodium(II)-catalyzed C-H amination reaction of (S)-3-(tert-butyldimethylsilyloxy)-2-methylpropyl carbamate: a facile preparation of optically active monoprotected 2-amino-2-methyl-1,3-propanediol

Dirhodium(II)-catalyzed C-H amination reaction of (S)-3-(tert-butyldimethylsilyloxy)-2-methylpropyl carbamate, which was easily prepared from methyl (S)-2-methyl-3-hydroxypropanoate, proceeded more smoothly than those of their 2-(methoxycarbonyl)propyl derivative to give the corresponding oxazolidinone in excellent yield. The resulting oxazolidinone was converted efficiently into both (R)-monoprotected and (S)-monoprotected 2-amino-2-methyl-1,3-propanediols.     

Selective ultratrace detection of Al(III) and Ga(III) complexed with a calcein isomer by capillary zone electrophoresis with laser-induced fluorescence detection. Comparison of emissive polyaminocarboxylates as derivatizing ligands

A highly sensitive and selective capillary zone electrophoresis with laser-induced fluorescence detection (CZE-LIF) for Al(3+) and Ga(3+) was developed using a calcein 4',5'-isomer as a pre-capillary complexing agent. Direct fluorescent detection without an agent added to the carrier buffer provided the notable detection limits of 3.9x10(-10) and 4.6x10(-10)moldm(-3) for Al and Ga, respectively. By applying this system successfully to a river water sample, its potential for practical applications was ascertained. A comparison of three aromatic polyaminocarboxylate ligands related to the coordination structure and the distance between the fluorophore and the chelating moiety, revealed some interesting factors regarding their selectivity.     

Hydrogen removal by annealing from C-doped InGaAs grown on InP by metalorganic chemical vapor deposition

Hydrogen removal from C-doped InGaAs grown on InP substrate by metalorganic chemical vapor deposition is discussed based on the dependence of hole concentration on various annealing conditions. It is revealed that the hydrogen removal rate becomes higher as the annealing temperature is higher and the activation energy of hydrogen removal is about 1.9 eV regardless of C-doped layer thickness. The hydrogen removal rate is also found to be inversely proportional to C-doped layer thickness, suggesting that the hydrogen removal reaction is mainly governed by hydrogen diffusion.     

Birefringence simulation of annealed ingot of magnesium fluoride single crystal

We developed a method for simulating birefringence of an annealed ingot of MgF₂ single crystal for lithography optics. This method provides the optical path difference caused by crystal symmetry and residual stress existing in the crystal. The method consists of the heat conduction analysis, the residual stress analysis and the birefringence analysis. Because there exists no experimental data on the inelastic behavior of MgF₂ single crystal, the residual stress was estimated with the elastic thermal stress analysis using the finite element method by assuming a stress-free temperature. In this analysis, the temperature dependence of material properties and crystal anisotropy were taken into account. In the birefringence analysis, the distributions of optical path difference were calculated by an approximate method using the result of the residual stress analysis. This approximate method uses the average stress along the wave normal and is equivalent to the exact method in case of low stress dealt with the present study. In this analysis, it is possible to consider both the intrinsic birefringence and the stress birefringence in any crystal orientation. The distribution of the optical path difference in the annealed ingot obtained from the present calculation agrees qualitatively with that of the experiment. Its calculated value also agrees reasonably well with that of the experiment, when a stress-free temperature is adequately selected.     

Preparation of polysiloxanes from silicic acid. III. Preparation and properties of polysilicic acid butyl esters

Polysilicic acid butyl esters were prepared from 1-butanol and silicic acid extracted from sodium metasilicate solution and water glass with tetrahydrofuran and hydrochloric acid. The properties of the esters were dependent on the degree of esterification (DE). The esters with a DE of less than ca. 60% could be isolated by precipitation with hexane and were highly liable to self-condensation, whereas those with more than 60% DE were soluble in solvents and could not be precipitated easily. They underwent further condensation to form highly polymerized esters. Subsequent silylation allowed the isolation and characterization of these esters. The solvent-soluble silylated esters had moderate thermal stability with decomposition points between 210 and 260°C and number-average molecular weights of 10,000–30,000. From the evaluation of units structures of silylate it was suggested that polymer backbone was a pseudoladder structure.     

Preparation and photolysis of polyamides having coumarin dimer component

The ring-opening polyaddition reaction of anti and syn head-to-head Coumarin dimers with diamines and the photocleavage behavior of the resulting polyamides were investigated. Anti head-to-head Coumarin dimer successfully reacted with aliphatic and aromatic diamines in an aprotic polar solvent to give corresponding high molecular weight polyamides. The polyamides showed good film forming ability and exhibited solubility behavior typical of polyelectrolytes. Furthermore, these polyamides were found to undergo exclusively asymmetric photocleavage on the cyclobutane rings in the polymer main chain to give a fumaramide unit with elimination of 2,2′-dihydroxystilbene. On the other hand, syn head-to-head Coumarin dimer gave only low molecular weight polyamides. These polymerization and photocleavage behaviors were elucidated in comparison with those of model reactions.