Highly chemo- and regioselective phosphitylation of unprotected 2′-deoxyribonucleosides

We have developed the chemo- and regioselective phosphitylation of unprotected 2′-deoxyribonucleosides by the use of di-tert-butyl N,N-diethylphosphoramidite, a sterically hindered phosphoramidite. Both N/O- and primary hydroxy group-selectivities were simultaneously achieved, and the selectivity for the 5′-hydroxy groups was up to 97% regardless of the base moiety of the 2′-deoxyribonucleosides. The 3′-O-isomers and the 5′-O-isomers were easily separated by silica gel column chromatography or crystallization to give the pure 2′-deoxyribonucleoside 5′-phosphites in moderate to good yields.     

Calorimetric study of the glassy state XII. Plural glass-transition phenomena of ethanol

Ethanol was found to give a metastable crystalline phase (crystal-II) when the liquid was cooled at a moderate rate. Glassy states of liquid and of newly found crystal-II were obtained in the calorimeter cell by controlling the cooling rate of the liquid. The heat capacities of these phases as well as that of the stable crystal-I were measured by an adiabatic calorimeter in the temperature range between 14 and 300 K. The glass transition temperature T_g, the heat-capacity jump at T_g, and the residual entropy were found to be 97 K, 35.3 J K^?1 mol^?1, and 8.93 J K^?1 mol^?1 for the glassy liquid, and 97 K, 22.8 J K^?1 mol^?1, and 4.24 J K^?1 mol^?1 for the glassy crystal-II, respectively. The values for the residual entropy are referred to the third-law entropy for crystal-I.The heat capacities reported previously for the supercooled liquid by Gibson et al. and by Parks and Kelley agree well with those for the metastable crystal-II. Those of the supercooled liquid connect smoothly with those obtained for the liquid above the melting temperature. Thus, ethanol is found to be another example of a low-molecular-weight compound which shows multiple glass-transition phenomena.     

Diastereoselective Iodocarbocyclization Reaction of 2- or 3-Oxy-4-pentenylmalonate Derivatives

1,2- Or 1,3-asymmetric induction in the iodocarbocyclization reaction of 4-pentenylmalonate derivatives having a stereogenic center at an allylic or a homoallylic position has been investigated. The iodocarbocyclization reactions of 3-oxy-4-pentenylmalonate derivatives proceeded with high cis-selectivity through stereoelectronic control of the oxygenated substituent at an allylic position. In the reaction of (S)-2-siloxy-4-pentenylmalonate, an excellent diastereoselectivity was achieved through the utilization of double stereodifferentiation with a chiral titanium catalyst. Furthermore, as an application of the present reaction, the asymmetric syntheses of cyclosarkomycin and a synthetic intermediate of brefeldin A from optically pure 2- and 3-oxy-4-pentenylmalonate derivatives are also described.     

Assembly of azido- or cyano-bridged binuclear complexes containing the bulky [Mn(phen)2]2+ building block: syntheses, crystal structures, and magnetic properties

Two new cyano-bridged heterobinuclear complexes, [Mn(II)(phen)2Cl][Fe(III)(bpb)(CN)2] x 0.5CH3CH2OH x 1.5H2O (1) and [Mn(II)(phen)2Cl][Cr(III)(bpb)(CN)2] x 2H2O (2) [phen = 1,10-phenanthroline; bpb(2-) = 1,2-bis(pyridine-2-carboxamido)benzenate], and four novel azido-bridged Mn(II) dimeric complexes, [Mn2(phen)4(mu(1,1)-N3)2][M(III)(bpb)(CN)2]2 x H2O [M = Fe (3), Cr (4), Co (5)] and [Mn2(phen)4(mu(1,3)-N3)(N3)2]BPh4 x 0.5H2O (6), have been synthesized and characterized by single-crystal X-ray diffraction analysis and magnetic studies. Complexes 1 and 2 comprise [Mn(phen)2Cl]+ and [M(bpb)(CN)2]- units connected by one cyano ligand of [M(bpb)(CN)2]-. Complexes 3-5 are doubly end-on (EO) azido-bridged Mn(II) binuclear complexes with two [M(bpb)(CN)2]- molecules acting as charge-compensating anions. However, the Mn(II) ions in complex 6 are linked by a single end-to-end (EE) azido bridging ligand with one large free BPh4(-) group as the charge-balancing anion. The magnetic coupling between Mn(II) and Fe(III) or Cr(III) in complexes 1 and 2 was found to be antiferromagnetic with J(MnFe) = -2.68(3) cm(-1) and J(MnCr) = -4.55(1) cm(-1) on the basis of the Hamiltonian H = -JS(Mn)S(M) (M = Fe or Cr). The magnetic interactions between two Mn(II) ions in 3-5 are ferromagnetic in nature with the magnetic coupling constants of 1.15(3), 1.05(2), and 1.27(2) cm(-1) (H = -JS(Mn1)S(Mn2)), respectively. The single EE azido-bridged dimeric complex 6 manifests antiferromagnetic interaction with J = -2.29(4) cm(-1) (H = -JS(Mn1)S(Mn2)). Magneto-structural correlationship on the EO azido-bridged Mn(II) dimers has been investigated.     

Nature of the active component in the catalytic system prepared from titanium(III) chloride(AA), ethylaluminum dichloride,and tetrakis(dimethylamino)silane,in the polymerization of propylene

The chemistry of the titanium(III) chloride(AA)–ethylaluminum dichloride–tetrakis-(dimethylamino)silane system for the polymerization of propylene was studied. A complex of ethylaluminum dichloride with tetrakis(dimethylamino)silane was isolated. It was shown that this complex contains ethylaluminum dichloride and tetrakis(dimethylamino)silane in the ratio of 2:1. This complex with titanium(III) chloride is responsible for the polymerization activity.     

One-dimensional ion transport in self-organized columnar ionic liquids

New fan-shaped ionic liquids forming columnar liquid crystalline phases have been prepared to obtain one-dimensional ion-transporting materials. The ionic liquids consist of two incompatible parts: an imidazolium-based ionic part as an ion-conducting part and tris(alkyloxy)phenyl parts as insulating parts. Two compounds having octyl and dodecyl chains have been synthesized. Self-assembly of these materials leads to the formation of thermotropic hexagonal columnar liquid crystalline states at room temperature. Anisotropic one-dimensional ionic conductivities have been successfully measured by the cells having comb-shaped gold electrodes. The self-organized columns have been aligned macroscopically in two directions by shearing perpendicular and parallel to the electrodes. The ionic conductivities parallel to the column axis are higher than those perpendicular to the axis. The incorporation of lithium salts in these columnar materials leads to the enhancement of the ionic conductivities and their anisotropy. These materials would be useful for anisotropic transportation of ions at the nanometer level.     

Modern microscopy methods for the structural study of porous materials

This article describes a number of important recent microscopy tools and their application in particular to the study of porous inorganic materials. The authors believe that these new techniques are on the threshold of delivering enormous new power in the chemist's arsenal for understanding new and complex behaviour in multi-component, hierarchical or composite materials. In particular we consider the contribution of electron crystallography, three-dimensional electron tomography, ultra-high resolution scanning electron microscopy as well as the combined application of high-resolution electron microscopy and atomic force microscopy to the study of surfaces and crystal growth. Much of this work has taken on a particular significance owing to the ground breaking work of scientists at Mobil and in Japan 10 years ago in the successful synthesis of materials with porosity on many length scales achieved through the cooperative self-assembly between inorganic and organic phases. This resulted in a series of materials known as M41S of which MCM-41 and MCM-48 were two of the first and most important structures to be synthesised. This has led to a wealth of new porous structures with order over many length scales and has presented new problems in characterisation. Microscopy methods properly executed are particularly important in the study of this new class of material.     

Quantitative study of diffuse increased 99mTc-methylene diphosphonate accumulation of both kidneys

Patients with diffuse increased accumulation in both kidneys on 99mTc-MDP bone scintigram were evaluated quantitatively. Among 1,100 cases, 7 (0.63%) showed this finding. The accumulation density ratios of kidneys/lumbal vertebra in A/D exchanged images of these patients were compared with control group, so that these ratios of patient group were higher than control group statistically. In conclusion, the accumulation density ratio was made the index of diffuse increase accumulation in both kidneys on 99mTc-MDP bone scintigram.     

Isolation of heptadepsin, a novel bacterial cyclic depsipeptide that inhibits lipopolysaccharide activity

Lipopolysaccharide (LPS) is considered to cause various inflammatory reactions. We searched among microbial secondary metabolites for compounds that could inhibit LPS-stimulated adhesion between human umbilical vein endothelial cells (HUVEC) and human myelocytic cell line HL-60 cells. In the course of our screening, we isolated a novel cyclic depsipeptide, which we named heptadepsin, from the whole culture broth of Paenibacillus sp. The addition of heptadepsin prior to LPS stimulation decreased HL-60 cell-HUVEC adhesion without showing any cytotoxicity. It also inhibited the cellular adhesion induced by lipid A, the active component of LPS, but it did not inhibit TNF-alpha or IL-1beta-induced cell adhesion. The result of surface plasmon resonance (SPR) analysis revealed that heptadepsin interacted with lipid A directly. Thus, heptadepsin, a novel naturally occurring cyclic heptadepsipeptide, was shown to inactivate LPS by direct interaction with LPS.     

Mono- and oligosaccharide sensing by phenylboronic acid-appended 5,15-bis(diarylethynyl)porphyrin complexes

Porphyrin derivatives bearing a pair of boronic acid groups (1, 1·Zn, and 1·Cu) were designed and synthesized from 2 to construct a saccharide sensing system. Compounds 1, 1·Zn, and 1·Cu have a diethynyl porphyrin rotational axis, which is expected to act as a saccharide-binding modulator. Saccharide binding studies were conducted by UV-vis, fluorescence, and circular dichroism (CD) spectroscopies. In a water-methanol 1:1 (v/v) mixed solvent, we have found that 1·Zn can bind mono- and oligosaccharides including Lewis oligosaccharides to produce 1:1 host-saccharide complexes with the association constants of 10²−10³ M⁻¹ range. This paper thus demonstrates a new principle to design a boronic acid-based saccharide receptor.