Assembly of Carbohydrates on a Nickel(II) Center by Utilizing N-Glycosidic Bond Formation with Tris(2-aminoethyl)amine (tren). Syntheses and Characterization of [Ni{N-(aldosyl)-tren}(H(2)O)](2+), [Ni{N,N'-bis(aldosyl)-tren}](2+) and [Ni{N,N',N"-tris(aldosyl)-tren}](2+)

Reactions of [Ni(tren)(H(2)O)(2)]X(2) (tren = tris(2-aminoethyl)amine; X = Cl (1a), Br (1b); X(2) = SO(4) (1c)) with mannose-type aldoses, having a 2,3-cis configuration (D-mannose and L-rhamnose), afforded {bis(N-aldosyl-2-aminoethyl)(2-aminoethyl)amine}nickel(II) complexes, [Ni(N,N'-(aldosyl)(2)-tren)]X(2) (aldosyl = D-mannosyl, X = Cl (2a), Br (2b), X(2) = SO(4) (2c); aldosyl = L-rhamnosyl, X(2) = SO(4) (3c)). The structure of 1c was confirmed by X-ray crystallography to be a mononuclear [Ni(II)N(4)O(2)] complex with the tren acting as a tetradentate ligand (1c.2H(2)O: orthorhombic, Pbca, a = 15.988(2) ?, b = 18.826(4) ?, c = 10.359(4) ?, V = 3118 ?(3), Z = 8, R = 0.047, and R(w) = 0.042). Complexes 2a,c and 3c were characterized by X-ray analyses to have a mononuclear octahedral Ni(II) structure ligated by a hexadentate N-glycoside ligand, bis(N-aldosyl-2-aminoethyl)(2-aminoethyl)amine (2a.CH(3)OH: orthorhombic, P2(1)2(1)2(1), a = 16.005(3) ?, b = 20.095(4) ?, c = 8.361(1) ?, V = 2689 ?(3), Z = 4, R = 0.040, and R(w) = 0.027. 2c.3CH(3)OH: orthorhombic, P2(1)2(1)2(1), a = 14.93(2) ?, b = 21.823(8) ?, c = 9.746(2) ?, V = 3176 ?(3), Z = 4, R = 0.075, and R(w) = 0.080. 3c.3CH(3)OH: orthorhombic, P2(1)2(1)2(1), a = 14.560(4) ?, b = 21.694(5) ?, c = 9.786(2) ?, V = 3091 ?(3), Z = 4, R = 0.072, and R(w) = 0.079). The sugar part of the complex involves novel intramolecular sugar-sugar hydrogen bondings around the metal center. The similar reaction with D-glucose, D-glucosamine, and D-galactosamine, having a 2,3-trans configuration, resulted in the formation of a mono(sugar) complex, [Ni(N-(aldosyl)-tren)(H(2)O)(2)]Cl(2) (aldosyl = D-glucosyl (4b), 2-amino-2-deoxy-D-glucosyl (5a), and 2-amino-2-deoxy-D-galactosyl (5b)), instead of a bis(sugar) complex. The hydrogen bondings between the sugar moieties as observed in 2 and 3 should be responsible for the assembly of two sugar molecules on the metal center. Reactions of tris(N-aldosyl-2-aminoethyl)amine with nickel(II) salts gave the tris(sugar) complexes, [Ni(N,N',N"-(aldosyl)(3)-tren)]X(2) (aldosyl = D-mannosyl, X = Cl (6a), Br (6b); L-rhamnosyl, X = Cl (7a), Br (7b); D-glucosyl, X = Cl (9); maltosyl, X = Br (10); and melibiosyl, X = Br (11)), which were assumed to have a shuttle-type C(3) symmetrical structure with Delta helical configuration for D-type aldoses on the basis of circular dichroism and (13)C NMR spectra. When tris(N-rhamnosyl)-tren was reacted with NiSO(4).6H(2)O at low temperature, a labile neutral complex, [Ni(N,N',N"-(L-rhamnosyl)(3)-tren)(SO(4))] (8), was successfully isolated and characterized by X-ray crystallography, in which three sugar moieties are anchored only at the N atom of the C-1 position (8.3CH(3)OH.H(2)O: orthorhombic, P2(1)2(1)2(1), a = 16.035(4) ?, b = 16.670(7) ?, c = 15.38(1) ?, V = 4111 ?(3), Z = 4, R = 0.084, and R(w) = 0.068). Complex 8 could be regarded as an intermediate species toward the C(3) symmetrical tris(sugar) complexes 7, and in fact, it was readily transformed to 7b by an action of BaBr(2).     

Synthesis, complexation, and fluorescence behavior of armed crown ethers carrying naphthyl group

Armed crown ethers (1-4) bonding through an amine, amide, ether, or ester linkage to naphthyl group were found to display unique photophysical properties in the presence of guest salts. Complexation of PET fluoroionophores (1a and 1b) with Zn(2+) increased the fluorescence intensities of the host by a factor of 2.4 and 2.7, respectively. (1)H and (13)C NMR analyses of this complexation behavior of 1a revealed that Zn(2+) strongly coordinates with the armed crown nitrogen to cause a dramatic decrease in an intramolecular charge-transfer character. The armed crowns (2 and 3), bonding through an ether or ester linkage to a naphthalene, gave fluorescence quenching with guest thiocyanates. While the amide derivative (4) exhibited high Ba(2+) fluorescence selectivity and in the presence of this cation the host fluorescence intensity was by a factor of 3.69.     

Complexation and fluorescence behavior of diazacrown ether carrying two anthryl pendants

Photoinduced electron transfer (PET) fluoroionophores (1b, 2b) that consist of diazacrown and two 9-anthryl pendants show fluorescent enhancement with various guest salts. The diaza-12-crown-4 derivative (2b) exhibited Zn(2+) selectivity and in the presence of this cation the host fluorescence intensity was increased by a factor of 182. The guest cation-induced fluorescence enhancement of 2b was larger than the diaza-18-crown-6 derivative (1b).     

Crystalline‐Sponge‐Based Structural Analysis of Crude Natural Product Extracts

Characterization of complex natural product mixtures to the absolute structural level of their components often requires significant amounts of starting materials and lengthy purification process, followed by arduous structure elucidation efforts. The crystalline sponge (CS) method has demonstrated utility in the absolute structure elucidation of isolated organic compounds at miniscule quantities compared to conventional methods. In this work, we developed a new CS‐based workflow that greatly expedites the in‐depth structural analysis of crude natural product extracts. Using a crude extract of the red alga Laurencia pacifica, we showed that CS affinity screening prior to compound isolation enables prioritization of analytes present in the extract, and we subsequently resolved the molecular structures of six sesquiterpenes with stereochemical clarity from around 10 mg crude extract. This study demonstrates a new chemotyping workflow that can greatly accelerate natural product discovery from complex samples.     

10B quantitative determination in ppb range by particle tracks reading for boron neutron capture therapy

Quantitative determination of ppb-order ¹⁰B was carried out in a small number of cultured tumor cells by particle tracks by the ₁₀B(n,)⁷Li reactions using solid state nuclear track detector (SSNTD) for boron neutron capture therapy research. The detection limit of ¹⁰B concentration in tumor cells is less than 1·10^-3 ppm under our experimental conditions which permits the quantitative determination of ¹⁰B in a small number of boronated tumor cells (10⁵/ml = ca. 0.1 mg). Boron quantities in tumor cells determined were well compatible with the tumor cell killing effects of boron neutron capture therapy.     

Novel phenoxyalkylamine derivatives. VII. Synthesis and pharmacological activities of 2-alkoxy-5-[(phenoxyalkylamino)alkyl]benzenesulfonamide derivatives.

To find a novel alpha-blocker with high alpha-blocking selectivity against dopamine D2-receptor affinity, we performed structural modification of the alkylene chains and the substituents on two benzene rings of 2-alkoxy-5-[(phenoxyalkylamino)alkyl]benzenesulfonamide derivatives. The modification of the alkylene chain between the amino moiety in the center of the molecule and the benzene ring (ring A) was found to be the most significant. 5-[2-[[2-(5-Fluoro-2-methoxyphenoxy)ethyl]amino]propyl]-2- methoxybenzenesulfonamide (II-4), which possesses 1-methylethyl as the alkylene chain, exhibited high alpha-blocking selectivity as well as potent alpha-blocking activity.     

Site-specific cleavage of glycated human serum albumin in the presence of iron.

Nonenzymatically glycated human serum albumin was incubated with ferric ion at 37 degrees C in 0.2 M phosphate buffer, pH 7.4, up to 30 days. In the incubation mixture, amino acids, tyrosine and phenylalanine, were detected, suggesting site specific cleavage of glycated human serum albumin.     

Convection in the presence of a first-order phase change

We report experimental and theoretical results for two-phase convection in a thin horizontal layer of a fluid with a first-order phase change and heated from below. A top layer of the nematic phase of a liquid crystal is located above the bottom layer of the isotropic phase of the same substance. A horizontal field of 1000 G is applied in order to align the director of the nematic phase. Over some ranges of the thickness of the isotropic phase, and in sufficiently large thermal gradients, the more dense nematic phase can be stably stratified above the less dense isotropic one, with a stable interface between them. Based on the equations of motion derived for this problem by Busse and Schubert [J. Fluid Mech. 46, 801 (1971)], we evaluate the bifurcation lines between the quiescent and convecting states and the corresponding critical wave vectors as a function of the interface position. We report experimental measurements based on Nusselt-number determinations for the locations of the bifurcation lines. They are in good agreement with the theoretical results. We also report approximate determinations of the critical wave numbers which are semiquantitatively consistent with the theory. A great diversity of patterns is observed in the convecting states, including normal and parallel rolls, rolls with defects and disorder, target patterns and spirals, and cellular flow with upflow or downflow at the cell center. These patterns are discussed in terms of the breaking of the mirror symmetry at the horizontal midplane by the interface, and in terms of the orienting effects of the magnetic field.