Diastereoselective Synthesis of a Hydroazulene Derivative by Tandem Michael-Wittig Reactions

The reaction of a cyclic phosphonium ylide [ 1 ] with enoate 2 gives a hydroazulene derivative with stereoselectivity.     

3,4-Thienylene-ethynylene Oligomers

Several well-defined 3,4-thienylene-ethynylene oligomers with different chain lengths have been synthesized and characterized. X-Ray crystallographic analyses proved their unique, totally helical conformations.     

Carrier removal by implanted IONS in GaAs

Abstract

A model for calculation of the range distribution of energetic ions with taking into account the channeling effect is proposed. The measurement of the depth distributions of boron ions in silicon crystals implanted at 13.6 and 91 MeV revealed significant difference between the measured and the calculated range profiles when the channeling effects have not been included in the calculation. In spite of deminishing the critical angles of channeling with growing ion energy the probability of the capture of ions into the channeling regime is significant in case of high energy implantation even when the incident angles are 7–10° off the main crystallographic directions.     

Comparative investigation of Au nano-particle formation process dependent upon various protective agents

Formation process of gold nanoparticles was investigated by near-field heterodyne transient grating method. In the absence of the protective agents, although the diffusion of H[Au^ICl₂] could be observed after the photo-reduction of H[Au^IIICl₄], the diffusion of nanoparticle-seeds was not observed. On the other hand, in the presence of the protective agents, the diffusion of a complex molecule (Au and protective agent) and nanoparticle-seeds could be observed. From these results, it was found that enough amount of the complex is essential for the nanoparticle formation. We also investigated the formation process with four different chemicals as a protective agent. The hydrodynamic radius of nanoparticle-seeds generated in the poly(vinyl pyrrolidone) and TritonX-100 solutions were larger than those generated in the Tween 20 and Brij 58 solutions. The former two have hydrophilic chain in the molecular structure; on the other hand, the latter two have hydrophobic alkyl chain. Based on those facts, we concluded that the interaction between the chains of the complex molecule plays an important role in the nanoparticle formation process.     

Electrodeposition of aluminum–hafnium alloy from the Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride molten salt

The electrochemistry of Hf(IV) and the electrodeposition of Al–Hf alloys were examined in the Lewis acidic 66.7–33.3 mol% aluminum chloride-1-ethyl-3-methylimidazolium chloride molten salt containing HfCl₄. When cyclic staircase voltammetry was carried out at a platinum disk electrode in this melt, the deposition and stripping waves for Al shifted to negative and positive potentials, respectively, suggesting that aluminum stripping is more difficult due to the formation of Al–Hf alloys. Al–Hf alloy electrodeposits containing ~13 at.% Hf were obtained on Cu rotating wire and cylinder electrodes. The Hf content in the Al–Hf alloy deposits depended on the HfCl₄ concentration in the melt, the electrodeposition temperature, and the applied current density. The deposits were composed of dense crystals and were completely chloride-free. The chloride-induced pitting corrosion potential of the resulting Al–Hf alloys was approximately +0.30 V against pure aluminum when the Hf content was above 10 at.%.     

Hydrochlorothiazide Enhances UVA‐Induced DNA Damage

The UVA is currently thought to be carcinogenic because, similar to UVB, it induces the formation of cyclobutane pyrimidine dimers (CPDs). Various drugs have been reported to cause photosensitive drug eruptions as an adverse effect. Although the precise mechanism of photosensitive drug eruption remains to be elucidated, it is generally accepted that free radicals and other reactive molecules generated via UV‐irradiated drugs play important roles in the pathogenesis of photosensitive drug eruptions. The waveband of concern for photo‐reactive drugs is UVA‐visible light, but some extend into the UVB region. We tested whether photosensitive drugs could enhance CPD formation after UVA exposure by using isolated DNA in the presence of several reported photosensitive drugs using high‐performance liquid chromatography. We found that the diuretic agent hydrochlorothiazide (HCT) significantly enhanced the production of TT dimers over a wide range of UVA. Furthermore, we investigated whether UVA plus HCT could enhance CPD production in xeroderma pigmentosum model mice defective in nucleotide excision repair. Immunofluorescence studies showed that CPD formation in the skin significantly increased after 365 nm narrow‐band UVA irradiation in the presence of HCT, compared with that in wild‐type mice. HCT could be used with caution because of its enhancement of UVA‐induced DNA damage.     

Officinatrione: an unusual (17S)-17,18-seco-lupane skeleton,and four novel lupane-type triterpenoids from the roots of Taraxacum officinale

Novel 5 lupane-type of triterpenois, i.e., 3β-acetoxy-18α,19α-epoxylupan-21β-ol (1), 18α,19α-epoxy-21β-hydroxylupan-3-one (2), lup-18-ene-3,21-dione (3), lupa-18,21-dien-3β-yl acetate (4), and (17S)-17,18-seco-lup-19(21)-ene-3,18,22-trione (5), named officinatrione, as well as 16 known compounds from the roots of Taraxacum officinale collected in Takatsuki city, Osaka, Japan. Of the above compounds, 5 was the first lupane-type triterpene, of which the D-ring was open to form a nine-membered ring. Compounds 2 and 5 exhibited moderate cytotoxic activities against L1210 cell line (IC₅₀ 10.5 and 10.1 μM).