A highly stereoselective samarium diiodide-promoted aldol reaction with 1'-phenylseleno-2'-keto nucleosides. Synthesis of 1'alpha-branched uridine derivatives

Since 1'-branched nucleosides are biologically important targets in medicinal chemistry, more efficient methods for preparing them are required. The 1'alpha-branched uridine derivatives were successfully synthesized via a samarium diiodide (SmI(2))-promoted aldol reaction. Treatment of the 1'alpha-phenylseleno-2'-ketouridine derivative 6, readily prepared from uridine, with SmI(2) at -78 degrees C in THF reductively cleaved the anomeric Se-C bond to generate the corresponding samarium enolate, which was highly stereoselectively condensed with aldehydes, such as PhCHO, MeCHO, i-PrCHO, or (CH(2)O)(n)(), to give the corresponding 1'alpha-1' 'S-branched products 12a-d. This is the first time an enolate has been generated by reductively cleaving a C-Se bond. The highly selective stereochemical results suggest that the aldol reaction proceeds via a chelation-controlled transition state. When an excess of aldehyde was used and the reaction mixture was gradually warmed, the tandem aldol-Tishchenko reaction proceeded to give the "arabino-type" nucleosides 14a-c, having a 2'-"up" hydroxyl and 1'alpha-1' 'S-branched chain. 1'alpha-Hydroxymethyluridine (21), which is the uracil version of the antitumor antibiotic angustmycin C, was synthesized from the aldol reaction product 10.     

The electronic structures of aminopyridines and their mono- and di-protonated cations

Using a semi-empirical ASMO SCF method for valence electron systems previously proposed by the present authors, the electronic structures of aminopyridines and their mono- and di-protonated cations are calculated. It is explained that the mono-protonation occurs on the ring nitrogen atoms and the di-protonation takes place on the nitrogen atoms both in the ring and the amino group. The electron migration to the added protons are calculated to be about 0.7 e for all the cations treated. The calculated results for n – ^* and – ^* singlet transitions of aminopyridines and their protonated cations show fairly good agreement with the experimental results. The electronic structures of pyridone imines, the tautomeric isomers of aminopyridines, are also briefly discussed.

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Zusammenfassung Mittels eines semiempirischen ASMO SCF-Verfahrens wird die Elektronenstruktur von Aminopyridinen und ihrer mono- und diprotonierten Kationen berechnet. Die erste Protonierung findet am N-Atom im Ring und die zweite an der Aminogruppe statt. Für die Elektronenverschiebung zu den angelagerten Protonen ergibt sich in allen Fällen etwa 0,7 e. Die berechneten n - ^*- und - ^*- Singulettübergänge zeigen befriedigende Übereinstimmung mit dem Experiment. Schließlich wird noch die Elektronenstruktur von Pyridoniminen diskutiert.

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Résumé Calcul des structures électroniques des aminopyridines et de leurs cations mono- et di-protonés, en utilisant une méthode semi-empirique ASMO SCF pour les électrons de valence proposée précédemment par les auteurs. On explique la mono-protonation sur les atomes d'azote du cycle et la di-protonation sur les atomes d'azote du cycle et du groupe aminé. Le transfert d'électron sur les protons supplémentaires est de l'ordre de 0,7 e pour tous les cations étudiés. Les résultats calculés pour les transitions singulets n ^* et ^* des aminopyridines et de leurs cations sont en bon accord avec l'expérience. Les structures électroniques des pyridone imines, tautomères des aminopyridines, sont brièvement discutées.

     

Optical sensor for the visual detection of mercury using mesoporous silica anchoring porphyrin moiety

A low cost, solid optical sensor for the rapid detection of low concentrations of Hg2+ in aqueous media was prepared by the monolayer functionalization of mesoporous silica with 5,10,15,20-tetraphenylporphinetetrasulfonic acid (TPPS), anchored by N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAC). The detection is based on the color change of TPPS from orange to green as a result of the formation of a charge-transfer complex with Hg2+. The intensity of the charge-transfer band varies linearly with Hg2+ in the concentration range from zero to 2.5 x 10(-7) mol dm(-3). The lower detection limit observed for Hg2+ concentration is 1.75 x 10(-8) mol dm(-3). The material exhibits good chemical and mechanical stability, and did not show any degradation of TPPS for a period of eight months. The sensor was applied for the analysis of various environmental samples. The effects of pH, sample volume, reaction time, amount of material, and the presence of foreign ions on the detection method are discussed.     

Pentacyclic laddersiloxane

A novel method which effects ring extension of the ladder oligosilsesquioxanes was developed. By applying this method, we synthesized the first functionalized tricyclic laddersiloxanes and pentacyclic laddersiloxane. The reaction of (i-PrSi(OH)O)4 with (i-PrPhClSiO)2 in pyridine gave the tetraphenyl tricyclic laddersiloxane. Following dephenylchlorination with AlCl3/HCl, and hydrolysis enabled us to isolate the tetrahydroxyl tricyclic laddersiloxane in good yield. We repeated the similar reaction from this tetrahydroxyl laddersiloxane, and the first pentacyclic laddersiloxane was obtained. The structures of the tetraphenyl and tetrahydroxyl tricyclic laddersiloxanes, and pentacyclic laddersiloxane were determined by X-ray crystallography.     

Entrapment of some compounds into biocompatible nano-sized particles and their releasing properties

Two types of biocompatible nanoparticles with an average diameter of around 200 nm were formed only by mixing hydrolysates of chitosan and carboxymethyl cellulose (CMC). Nanoparticle A was produced from chitosanase hydrolysate of chitosan and cellulase hydrolysate of carboxymethyl cellulose, and nanoparticle B was produced from lysozyme hydrolysate of chitosan and the carboxymethyl cellulose hydrolysate. Negatively charged or amphoteric compounds were first mixed with chitosan hydrolysate and then added to carboxymethyl cellulose hydrolysate to effectively entrap them in the particles. Positively charged compounds could also be effectively entrapped by mixing the hydrolysates and the compound in the reverse order. Negatively charged compounds with high molecular weights were maintained in the particles even at the higher pH levels than the pK(a) of the amino groups of chitosan. Entrapped compounds were gradually released from nanoparticle A by lysozyme treatment. In contrast, there was no release from nanoparticle B. These results indicate that nanoparticle A can be applied to controlled-release drug delivery systems, and that nanoparticle B is stably retained in the body without releasing the entrapped compounds.     

Characteristics of the asymmetric mass distribution in proton-induced fission of actinides

To study the correlation between fragment mass distributions and shell structures of fission fragments, fragment mass and energy distributions in proton-induced fission of ²³²Th and uranium isotopes, ^233,235,238U, were precisely measured using a double-TOF method. It was found that the lighter side of the heavier wing of asymmetric mass distributions shifts to larger fragment mass number corresponding to the N/Z value of the fissioning nucleus. The results are explained qualitatively by the change of the most probable mass number of fission fragments of Z = 50 proton-shell.     

Analysis of ″stepwise″ heterocoagulation process of small cationic polymer particles onto large anionic polymer particles using dynamic light scattering

In order to clarify in detail the process of the stepwise heterocoagulation of small polymer particles (SP) onto large polymer particles (LP), which we proposed to prepare anomalous polymer particles, the particle-size distribution in each step was estimated using dynamic light scattering.SP andLP have surface charges opposite to each other in emulsion states.SP were produced by emulsion copolymerization of styrene and methacryloyloxyethyltrimethylammonium chloride, andLP by emulsion terpolymerization of styrene, butyl acrylate, and methacrylic acid. Both emulsions in which nonionic emulsifier had been added were blended without coagulation and then the heterocoagulation was carried out by adjusting of the pH and heating.Part CXVII of the series Studies on Suspension and Emulsion.     

The Nehari problem for infinite-dimensional linear systems of parabolic type

A complete solution is obtained to the suboptimal Nehari extension problem for transfer functions of parabolic systems with Dirichlet boundary control and smooth observations. The solutions are given in terms of the realization (–A, B, C), whereA is a uniformly strongly elliptic operator of order two with smooth coefficients defined on a bounded open domain ofR _d ,B=AB _D andB _D is the Dirichlet map associated with Dirichlet boundary conditions andC is a bounded observation map fromL ₂() to the output spaceY. The approach is to solve an equivalentJ-spectral factorization problem for this particular realization.     

Theoretical study of lithium ionic conductors by electronic stress tensor density and electronic kinetic energy density

We analyze the electronic structure of lithium ionic conductors, and , using the electronic stress tensor density and kinetic energy density with special focus on the ionic bonds among them. We find that, as long as we examine the pattern of the eigenvalues of the electronic stress tensor density, we cannot distinguish between the ionic bonds and bonds among metalloid atoms. We then show that they can be distinguished by looking at the morphology of the electronic interface, the zero surface of the electronic kinetic energy density. © 2016 Wiley Periodicals, Inc.     

A Bioorthogonal Approach for the Preparation of a Titanium‐Binding Insulin‐like Growth‐Factor‐1 Derivative by Using Tyrosinase

The generation of metal surfaces with biological properties, such as cell‐growth‐enhancing and differentiation‐inducing abilities, could be potentially exciting for the development of functional materials for use in humans, including artificial dental implants and joint replacements. However, currently the immobilization of proteins on the surfaces of the metals are limited. In this study, we have used a mussel‐inspired bioorthogonal approach to design a 3,4‐hydroxyphenalyalanine‐containing recombinant insulin‐like growth‐factor‐1 using a combination of recombinant DNA technology and tyrosinase treatment for the surface modification of titanium. The modified growth factor prepared in this study exhibited strong binding affinity to titanium, and significantly enhanced the growth of NIH3T3 cells on the surface of titanium.