Selective generation of organic aggregates included within metal-organic micropores through vapor adsorption

The ethanol vapor adsorption behavior and the inclusion crystal structure of a 1D-transformable coordination polymer host were characterized. The adsorption jump was observed during phase transition or two-phase equilibrium with abnormal adsorption enthalpy caused by the nature of "mass induced phase transition." The included ethanol guests selectively form O-H...O hydrogen bonded pairs inside channels, suggesting selective construction of a specific cluster/aggregate in pores under control of thermodynamic factors and cooperative intermolecular interactions among the guest and channel surface.     

Hole doping and superconductivity characteristics of the s=1, 2 and 3 members of the (Cu,Mo)-12s2 homologous series of layered copper oxides

Superconductivity characteristics have been systematically evaluated for a two-CuO₂-plane copper oxide system, (Cu,Mo)-12s2, upon increasing the number of fluorite-structured layers, s, between the two CuO₂ planes. Essentially single-phase samples of (Cu_0.75Mo_0.25)Sr₂YCu₂O_7+δ (s=1), (Cu_0.75Mo_0.25)Sr₂(Ce_0.45Y_0.55)₂Cu₂O_9+δ (s=2) and (Cu_0.75Mo_0.25)Sr₂(Ce_0.67Y_0.33)₃Cu₂O_11+δ (s=3) were synthesized through a conventional solid-state route in air. To make the samples superconductive an additional high-pressure oxygenation (HPO) treatment was required. Such treatment (carried out at 5 GPa and 500 °C in the presence of 75 mol% Ag₂O₂ as an oxygen source to maximize the T_c) compressed the crystal lattice for the three members of the (Cu_0.75Mo_0.25)-12s2 series equally, i.e., by 0.01 Å for the a parameter and by 0.07 Å for the c parameter per formula unit. From both Cu L-edge and O K-edge XANES spectra the s=1 sample was found to possess the highest overall hole-doping level among the HPO samples. Accordingly it exhibited the best superconductivity characteristics. With increasing s, both the T_c (s=1: 88 K, s=2: 61 K, s=3: 53 K) and H_irr values got depressed, being well explained by the trend of decreasing CuO₂-plane hole concentration with increasing s as revealed from O K-edge XANES spectra for the same samples. Hence, the present results do not suggest any significant (negative) impact on the superconductivity characteristics from the gradually thickened fluorite-structured block itself.     

Study of salt permeation process into Vigna angularis using Ag/AgCl electrodes

In this work we report a novel method that can monitor in vivo the salt permeation process into a plant Vigna angularis using two Ag/AgCl electrodes. The method is based on the electromotive force (emf) measurement using two Ag/AgCl electrodes, one inserted into the V. angularis pith cavity and the other placed into saline ([NaCl]=1 M) surrounding the roots. Temporary change of emf ranging from 0 to ca. 0.115 V was measured in vivo using the system, and the possible physiological phenomenon during the period was discussed.     

Synthesis of a novel bridged nucleoside bearing a fused-azetidine ring, 3′-amino-3′,4′-BNA monomer

A novel bridged nucleic acid monomer, 3′-amino-3′-deoxy-5-methyl-3′-N,4′-C-methyleneuridine, was successfully synthesized via a useful and convenient azetidine ring formation under Staudinger's conditions. A ¹H NMR experiment and a PM3 calculation revealed that the sugar moiety of the novel bridged nucleic acid monomer, 3′-amino-3′,4′-BNA, was restricted to S-type conformation.     

NAD(P)+-NAD(P)H model. 38. Reduction of aldehyde by 1,4-dihydroquinolin derivative

Benzaldehyde are reduced to benzyl alcohol by a model compound of NAD(P)H almost quantitatively. Reductions of some other aldehydes are also mentioned.     

Engineered biosynthesis of plant polyketides: chain length control in an octaketide-producing plant type III polyketide synthase

The chalcone synthase (CHS) superfamily of type III polyketide synthases (PKSs) produces a variety of plant secondary metabolites with remarkable structural diversity and biological activities (e.g., chalcones, stilbenes, benzophenones, acrydones, phloroglucinols, resorcinols, pyrones, and chromones). Here we describe an octaketide-producing novel plant-specific type III PKS from aloe (Aloe arborescens) sharing 50-60% amino acid sequence identity with other plant CHS-superfamily enzymes. A recombinant enzyme expressed in Escherichia coli catalyzed seven successive decarboxylative condensations of malonyl-CoA to yield aromatic octaketides SEK4 and SEK4b, the longest polyketides known to be synthesized by the structurally simple type III PKS. Surprisingly, site-directed mutagenesis revealed that a single residue Gly207 (corresponding to the CHS's active site Thr197) determines the polyketide chain length and product specificity. Small-to-large substitutions (G207A, G207T, G207M, G207L, G207F, and G207W) resulted in loss of the octaketide-forming activity and concomitant formation of shorter chain length polyketides (from triketide to heptaketide) including a pentaketide chromone, 2,7-dihydroxy-5-methylchromone, and a hexaketide pyrone, 6-(2,4-dihydroxy-6-methylphenyl)-4-hydroxy-2-pyrone, depending on the size of the side chain. Notably, the functional diversity of the type III PKS was shown to evolve from simple steric modulation of the chemically inert single residue lining the active-site cavity accompanied by conservation of the Cys-His-Asn catalytic triad. This provided novel strategies for the engineered biosynthesis of pharmaceutically important plant polyketides.     

A study on the conformation-anomeric effect-stereoselectivity relationship in anomeric radical reactions,using conformationally restricted glucose derivatives as substrates

We previously theorized that, since the stereoselectivity of anomeric radical reactions is significantly influenced by the kinetic anomeric effect, which can be controlled by restricting the conformation of the radical intermediate, the proper conformational restriction of the pyranose ring of the substrates would therefore make highly alpha- and beta-stereoselective anomeric radical reactions possible. This theory was based on our previous results of the anomeric radical reactions with d-xylose derivatives as the substrates. We herein report the anomeric radical deuteration reactions with the conformationally restricted 1-phenylseleno-d-glucose derivatives, 2g and 3g, restricted in a (4)C(1)-conformation by an O-cyclic diketal moiety, and 4g, 5g, 6g, 7g, and 8g, restricted in a (1)C(4)-conformation by bulky O-silyl protecting groups. The radical deuterations with Bu(3)SnD, using the (4)C(1)-restricted substrates 2g and 3g, afforded the corresponding alpha-products (alpha/beta = 98:2) highly stereoselectively, whereas the (1)C(4)-restricted substrate 6g, having a trigonal (sp(2)) carbon substituent, i.e., -CHO, at the 5-position, selectively gave the beta-products (alpha/beta = 0:100). Thus, the stereoselectivity was significantly increased by the conformational restriction and was completely inverted by changing the substrate conformation from the (4)C(1)-form to the (1)C(4)-form. On the other hand, the deuterations with the (1)C(4)-restricted substrates 4g and 5g showed that the 1,5-steric effect due to the tetrahedral carbon substituent (-CH(2)OTIPS or -CH(2)OH) at the 5-axial position dominantly prevented the hydride transfer from the beta-face competing with the kinetic anomeric effect. This study suggests that, depending on the restricted conformation of the substrates to the (4)C(1)- or the (1)C(4)-form, the alpha- or beta-products would be obtained highly stereoselectively via anomeric radical reactions of hexopyranoses.     

Triethylborane-mediated hydrogallation and hydroindation: novel access to organogalliums and organoindiums

Hydrogallation of carbon[bond]carbon multiple bonds proceeds in the presence of triethylborane as a radical initiator. Several functionalities do not interfere with this reaction. Resulting alkenyl- and alkylgallium species can be trapped by several electrophiles. Highly regioselective radical addition of an indium hydride reagent to alkynes is also achieved. Various functionalities are tolerant under the reaction conditions. The reaction proceeds with complete anti stereoselectivity. Alkenylindiums obtained via hydroindation can be employed for the following cross-coupling reaction with aryl halides in one pot.     

2-Silyl group effect on the reactivity of cyclopentane-1,3-diyls. Intramolecular ring-closure versus silyl migration

Generation of singlet and triplet 2-silylcyclopentane-1,3-diyls and their reactivity have been investigated in the thermal and photochemical denitrogenation of 2,3-diaza-7-silylbicyclo[2.2.1]hept-2-ene. 5-Silylcyclopentene (silyl migration product) is quantitatively obtained, while 5-silylbicyclo[2.1.0]pentane (intramolecular ring-closure product) is not detected in the denitrogenation reactions. Deuterium labeling studies clarify that 5-silylcyclopentene is formed by a suprafacial [1,2] silyl migration in singlet 2-silylcyclopentane-1,3-diyl. UDFT calculations closely reproduce the observed reactivity of the singlet diradical: The enthalpic barriers of the intramolecular ring-closure are calculated to be DeltaH++exo468 = 5.8 kcal/mol and DeltaH++endo468 = 6.7 kcal/mol, which are much higher than the energy barrier for the [1,2] silyl migration, DeltaH++468 = 2.7 kcal/mol. The notable effect of the silyl group on raising the energy barrier of the intramolecular cyclization is rationalized by an electronic configuration of the lowest singlet state of 2-silylcyclopentane-1,3-diyls.     

Detection of varicocele by using 99mTc-diethylenetriamine pentaacetic acid human serum albumin (99mTc-DTPA human serum albumin)

In order to detect the varicocele, scrotal scintigraphies by using 99mTc-HSA-D were performed in 14 patients with male infertile or palpable mass in left scrotum on physical examinations. Abnormal pooling of 99mTc-HSA-D, indicative of varicocele lesion, could be found in left scrotum in 9 cases, confirmed surgically or clinically. Compared with 99mTc-HSA, 99mTc-HSA-D was superior in high uptake ratio of varicocele to soft tissue and in nonvisualization of bladder. Thus, 99mTc-HSA-D scrotal scintigraphy seemed to be of a great use to detect the varicocele.