Cyclopropane-based stereochemical diversity-oriented conformational restriction strategy: histamine H3 and/or H4 receptor ligands with the 2,3-methanobutane backbone

The stereochemical diversity-oriented conformational restriction strategy can be an efficient method for developing specific ligands for drug target proteins. To develop potent histamine H(3) and/or H(4) receptor ligands, a series of conformationally restricted analogs of histamine with a chiral trans- or cis-4-amino-2,3-methano-1-(1H-imidazol-4-yl)butane structure was designed based on this strategy. These stereochemically diverse compounds were synthesized from previously developed versatile chiral cyclopropane units. Among these analogs, a trans-cyclopropane-type compound, (2S,3R)-4-(4-chlorobenzylamino)-2,3-methano-1-(1H-imidazol-4-yl)butane (5b), has remarkable antagonistic activity to both the H(3) (K(i) = 4.4 nM) and H(4) (K(i) = 5.5 nM) receptors, and a cis-cyclopropane-type compound, (2R,3R)-4-amino-2,3-methano-1-(1H-imidazol-4-yl)butane (6a), is a potent and selective H(3) receptor partial agonist (K(i) = 5.4 nM). Although (2S,3R)-4-amino-2,3-methano-1-(1H-imidazol-4-yl)butane (5a) does not have a hydrophobic group which the usual H(3) receptor antagonists have, it was found to be a potent H(3) receptor antagonist (K(i) = 20.1 nM). Thus, a variety of compounds with different pharmacological properties depending on the cyclopropane backbones and also on the side-chain functional groups were identified. In addition to the previously used 1,2-methanobutane backbone, the 2,3-methanobutane backbone also worked effectively as a cyclopropane-based conformational restriction structure. Therefore, the combination of these two cyclopropane backbones increases the stereochemical and three-dimensional diversity of compounds in this strategy, which can provide a variety of useful compounds with different pharmacological properties.     

Advanced chemical design with supported metal complexes for selective catalysis

This review covers several recent topics of novel catalyst design with supported metal complexes on oxide surfaces for selective catalysis such as chiral self-dimerization to create asymmetric oxidative coupling catalysis, surface functionalization with achiral reagents to promote asymmetric catalysis, and molecular imprinting to design shape-selective catalysis. The new concepts and designs find wide applications to a variety of selective catalysts.     

Tetrakis-acridinyl peptide: distance dependence of photoinduced electron transfer in deoxyribonucleic acid assemblies

A simple determination method for halogens (Cl, Br, and I) in plant samples using inductively coupled plasma-mass spectrometry (ICP-MS) was developed. In order to extract these halogens into aqueous solution, a leaching step with tetramethyl ammonium hydroxide (TMAH) under mild conditions was carried out, i.e. a 0.1-g dried sample was left overnight (ca. 12 h) in contact with 1 mL of 25% TMAH in a small PFA vial at 60 °C. Then the sample was transferred to a 50-mL centrifuge tube and diluted to 50 mL with deionised water. After centrifugation, halogens in the supernatant were determined by ICP-MS. When standard reference materials were measured by the method, the data were within the 95% confidence range of the certified values. The results also agreed well with the values obtained by neutron activation analysis with correlation factor r > 0.99.     

Encapsulation of small molecules by a cavitand porphyrin self-assembled via quadruple hydrogen bonds

A new and stable quadruple hydrogen-bonded capsule, tetracarboxylcavitand.meso-tetra(2-pyridyl)porphyrin (1 x 2) has been synthesized and spectroscopically characterized. 1 x 2 can encapsulate small molecules of various size from methane to cyclopentane. The guest and host exchange rates were evaluated by EXSY.     

Nuclear resonant time spectra for Sn in Co2TiSn Heusler alloy films

Co₂TiSn Heusler alloy films were grown on MgO substrates at the substrate temperature between 200 and 600 °C using atomically controlled alternate deposition and magnetic hyperfine field at the Sn nuclei was measured by the Mössbauer spectroscopy and the nuclear resonant scattering method. The relation between the hyperfine field and the structural disorder estimated by X-ray diffraction measurements was also examined. The results showed that the sample prepared at higher substrate temperature has higher degree of L2₁ order and larger hyperfine field. For the Co₂TiSn film grown at 600 °C, the hyperfine field estimated from the oscillatory pattern of the nuclear resonant time spectra was 6.1 T at room temperature and increased with a decrease of temperature to 7.5, 8.1, and 8.3 T at 200, 100, and 5 K, respectively, which shows that the film prepared by this method and condition has almost the same magnetization value and Curie temperature as bulk samples.     

Self-assembly of the light-harvesting complex of photosystem II (LHCII) on alkanethiol-modified gold electrodes

A light-harvesting complex of photosystem II (LHCII), isolated from spinach, was immobilized onto a gold electrode modified with self-assembled monolayers (SAMs) of alkanethiols, NH₂–(CH₂) _n –SH, n = 2, 6, 8, 11; HOOC–(CH₂)₇–SH; and CH₃–(CH₂)₇–SH; and a bare electrode. The extent of LHCII complex adsorption according to surface treatment decreased in the order amino groups > carboxylic acid groups > methyl groups and increased with the methylene chain length in NH₂–(CH₂) _n –SH. Interestingly, the photocurrent density depended on the terminal group and the methylene chain length in NH₂–(CH₂) _n –SH and decreased in the order amino groups > methyl groups > carboxylic acid groups. An efficient photocurrent response of the LHCII complex on SAMs of NH₂–(CH₂) _n –SH, n = 8 was observed upon illumination at 680 nm. These results indicated that the LHCII complexes were well organized on the cationic surfaces of the gold electrodes modified with amino alkanethiols. The quantum yield depended on the methylene chain length (n), where the maximum photocurrent response was observed at n = 8, which corresponded to a distance of 1.7 nm between the terminal amino group in NH₂–(CH₂)₈–SH and the gold surface.     

Ring cleavage and successive aldol reaction of 3-[(trialkylsilyl)methyl]cyclobutanones

3-[(Trialkylsilyl)methyl]cyclobutanones reacted with aldehydes by activation with titanium(IV) chloride to give acyclic β,γ-unsaturated β'-hydroxyketones.     

Studies on spintronics-related thin films using synchrotron-radiation-based Mössbauer spectroscopy

Applications of synchrotron-radiation-based Mössbauer spectroscopy in the “energy domain” to the studies on magnetism of thin films are introduced on the basis of the experiments recently performed at SPring-8, Japan. The measured samples are spintronics-related thin films, such as Co₂MnSn films, layered Fe/Cr films, layered Fe/Fe₃O₄ films, and Fe₄N films. The validity of the energy domain measurements is demonstrated in the light of industrial applications of magnetic thin films.