Platanionosides D-J: megastigmane glycosides from the leaves of Alangium platanifolium (Sieb. et Zucc.) Harms var. platanifolium Sieb. et Zucc

From the leaves of Alangium paltanifolium var. platanifolium, collected in Fukuoka Prefecture, twelve further megastigmane glycosides were isolated. Seven of them, named platanionosides D-J (1-7), were found to be new compounds. Their structures were elucidated from spectroscopic evidence and their absolute structures were determined from beta-D-glucosylation-induced shift trends of 13C-NMR and by application of a modified Mosher's method.     

Tareciliosides A--G: Cycloartane glycosides from leaves of Tarenna gracilipes (HAY.) OHWI

From the 1-BuOH-soluble fraction of a MeOH extract of leaves of Tarenna gracilipes, collected in Okinawa, seven new cycloartane glycosides, named tareciliosides A--G (4--10), were isolated together with three known compounds, D-mannitol (1), (R)-linalool 6-O-alpha-L-arabinopyranosyl-beta-D-glucopyranoside (2), and mussaenoside (3). Their structures were elucidated through a combination of spectroscopic analyses.     

Synthesis of polymers by use of divalent metal salts of monohydroxyethyl phthalate: Metal-containing isocyanurate-type crosslinked polyurethanes

Divalent metal salts (I) of monohydroxyethyl phthalate have catalytic activity for polymerization of isocyanate groups. The synthesis of novel metal-containing isocyanurate-type crosslinked polyurethanes were investigated by the crosslinking reaction of I in DMF with diisocyanates or urethane prepolymers, that is, diisocyanate adducts of polyethylene glycol. 2,4-Toluene diisocyanate and diphenylmethane diisocyanate were used as diisocyanates, and DMF was the solvent. The crosslinking reactions were followed by determining the gelation time. Gelation time decreased with increasing temperature. The Ca salt was more effective than the Mg salt in the crosslinking reaction. The yields of resulting metal-containing three-dimensional polymers decreased with increasing metal content in the feed. The Ca salt was more easily introduced into the network polymers than the Mg salt was. Decomposition temperatures decreased on introducing metals into the network polymers. Some physical properties of the metal-containing network polymers are also discussed.     

Preparation and characterization of silica—polyimide composite membranes coated on porous tubes for CO2 separation

Silica-polyimide microcomposite membranes were prepared on γ-alumina-coated α-alumina support tubes, and their gas permeation properties were evaluated with He, N₂ and CO₂. Smoothing of the substrate surface and hybridization of silica and polyamic acid were both effective to form defect-free thin composite membranes. The CO₂ permeance of a membrane with a silica content of 68 wt% was one order of magnitude higher than that of a polyimide membrane having the same thickness. The permselectivity of CO₂ to N₂ was 30 at 30°C and 13 at 100°C. Contributions of the silica and polyimide phases to permeance of the composite membrane were analyzed with a two-phase permeation model. The effective thickness of the rate-controlling polyimide phase was less than one-tenth of the total thickness of the silica-polyimide membrane.     

Stereoselective E/Z photoisomerization of oxazolidinone functionalized enecarbamates: direct and triplet sensitized irradiation

Oxazolidinone-functionalized enecarbamates undergo diastereoselective E/Z photoisomerization upon direct and triplet sensitized irradiations with chiral/achiral sensitizers, showing that the enhanced product diastereoselectivity depends on the solvent and temperature.     

Hydrogen analysis in solid samples by utilizing He metastable atoms induced by TEA CO2 laser plasma in He gas at 1 atm

A TEA CO₂ laser (350 mJ–1.5 J, 10.6 μm, 200 ns, 10 Hz) was focused onto a metal sub-target under He as host gas at 1 atmospheric pressure with a small amount of impurity gas, such as water and ethanol vapors. It was found that the TEA CO₂ laser with the help of the metal sub-target is favorable for generating a strong, large volume helium gas breakdown plasma at 1 atmospheric pressure, in which the helium metastable-excited state was then produced overwhelmingly. While the metal sub-target itself was never ablated. The helium metastable-excited state produced after the strong helium gas breakdown plasma was considered to play an important role in exciting the atoms. This was confirmed by the specific characteristics of the detected H emission, namely the strong intensity with low background, narrow spectral width, and the long lifetime. This technique can be used for gas and solid samples analysis. For nonmetal solid analysis, a metal mesh was introduced in front of the nonmetal sample surface to help initiation of the helium gas breakdown plasma. For metal sample, analysis can be carried out by combining the TEA CO₂ laser and an Nd–YAG laser where the Nd–YAG laser is used to ablate the metal sample. The ablated atoms from the metal sample are then sent into the region of helium gas breakdown plasma induced by the TEA CO₂ laser to be excited through the helium metastable-excited state. This technique can be extended to the analysis of other elements, not limited only to hydrogen, such as halogens.     

Spectral properties of the Cu-hyperaccumulating moss Scopelophilacataractae

To determine the characteristics of a Cu-hyperaccumulating moss Scopelophilacataractae and the influence of Cu on its structure and on chlorophyll (Chl), we measured reflectance and fluorescence (FL) spectra of S.cataractae samples with different Cu concentrations before and after wetting and the absorption spectra of Chl extracted from these samples. We found relationships between the spectral properties and Cu concentration. These relationships can be explained as follows. The higher the Cu concentration is, the lower is the plasticity of the cell wall, and the smaller is the increase in illuminated area due to the opening of the leaves after wetting. This results in a smaller increase in absorption and smaller decrease in reabsorption of the FL by Chl itself, and accordingly, a smaller increase in the FL band of Chl after wetting. Moreover, we found that the Chl concentration in S.cataractae is much higher than that in other common mosses and is correlated with an increase in the FL band of Chl after wetting. The remarkable increase in FL seen in S.cataractae and the slight increase in FL observed in other common mosses after wetting can be explained based on these findings.     

Synthesis of 4,6-disubstituted 2-methylpyridines and their 3-carboxamides

A new one-pot synthesis of title compounds by the reactions of α,β-unsaturated carbonyl compounds with β-aminocrotononitrile in the presence of sodium hydroxide is described.     

Aromaticity of planar boron clusters confirmed

Low-energy boron clusters are characterized by two-dimensional geometry. Aromaticity of these planar boron clusters was established in terms of topological resonance energy (TRE). All planar boron clusters were found to be highly aromatic with large positive TREs even if they have 4n pi-electrons. Aromaticity must therefore be the origin of unusual planar or quasi-planar geometry. Thus, the aromaticity concept is as useful in boron chemistry as it is in general organic chemistry. It is evident that the Hückel 4n + 2 rule of aromaticity should not be applied to such polycyclic pi-systems. Some of the boron clusters are in the triplet electronic state to attain higher aromaticity. Multivalency and electron deficiency of boron atoms are responsible for lowering the energies of low-lying pi molecular orbitals and then for enhancing aromaticity. For polycyclic pi-systems, paratropicity does not always indicate antiaromaticity.     

Tareciliosides H-M: further cycloartane glycosides from leaves of Tarenna gracilipes

From the 1-BuOH-soluble fraction of a MeOH extract of leaves of Tarenna gracilipes, collected in Okinawa, six further new cycloartane glycosides, named tareciliosides H-M (1-6), were isolated. Their structures were established through a combination of spectroscopic analyses.