Chiral aminoalcohol NOBIN for instantaneous chirality control of racemic but tropos BIPHEP-Rh(I)-complexes: highly enantioselective ene-type cyclization of 1,6-enynes catalyzed by the Rh(I)-complexes without use of acid

The tropos (chirally flexible) or atropos (chirally rigid) nature of BIPHEP-Rh complexes critically depends on amines and alcohols complexed. The BIPHEP-Rh complex with aminoalcohol NOBIN is significantly tropos and can be chirally controlled by aminoalcohol NOBIN instantaneously even at room temperature. The BIPHEP-Rh/NOBIN complex thus controlled can be used as an asymmetric catalyst to give higher enantioselectivity (up to 98% ee) and yield in ene-type cyclization of 1,6-enynes without use of acid.     

Colorimetric chemosensor for Fe<Superscript>2+</Superscript> and Fe<Superscript>3+</Superscript> based on a ternary mixture of an anionic dye,a cationic polyelectrolyte,and a metal chelator in aqueous solution

A new colorimetric chemosensor based on a simple ternary mixture of an anionic dye, pyrogallol red (PR), a cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDADMAC), and a metal chelator, N-(2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA) for the colorimetric detection of Fe²⁺ and Fe³⁺ has been developed in an aqueous solution buffered at pH 5. Upon addition of Fe²⁺ or Fe³⁺ to the mixture, the absorption spectra showed a bathochromic shift; correspondingly, the solution color changed from red to blue, whereas other metal ions basically resulted in insignificant spectral and color changes. From the competitive experiments, no obvious interferences for the colorimetric detection of Fe²⁺ and Fe³⁺ were observed in the presence other metal ions. The results indicated that the mixture could be used as a potential Fe²⁺ and Fe³⁺ colorimetric and naked eye chemosensor in aqueous media. This research demonstrates that the ternary ensemble consisted of an organic dye, an oppositely charged polyelectrolyte, and a metal chelator is a versatile and convenient tool for the facile preparation of a novel chemosensor system.     

Enantioselective catalysis of carbonyl-ene and Friedel–Crafts reactions with trifluoropyruvate by ‘naked’ palladium(II) complexes with SEGPHOS ligands

Chiral dicationic SEGPHOS–Pd(II) complex gives high chemical yield, (E)-olefin selectivity, anti-diastereoselectivity, along with high enantioselectivity even with less reactive mono- and 1,2-disubstituted olefins in this much less reactive ketone-ene reactions. The high levels of enantioselectivity not only in carbonyl-ene but also in Friedel–Crafts reactions stem from the effective shielding with diphenyl groups on phosphines caused by the narrow dihedral angle of metal complexes with SEGPHOS.     

Hydrolysis of ethyl acetate on cation-form sulfonic resins

Catalytic properties of metal cations on sulfonic resin have been studied in ester hydrolysis. The catalytic activities were related to the electronegativity of the metal cation, while the activation energies were close to that for H-form resin and not affected by the cation concentration, suggesting the variation of entropy factors in catalysis.

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Orally active CCR5 antagonists as anti-HIV-1 agents 2: synthesis and biological activities of anilide derivatives containing a pyridine N-oxide moiety

In order to develop orally active CCR5 antagonists, we investigated 1-benzoxepine derivatives containing new polar substituents, such as phosphonate, phosphine oxide or pyridine N-oxide moieties, as replacements for the previously reported quaternary ammonium moiety. Among these compounds, the 2-(alpha-hydroxybenzyl)pyridine N-oxide 5e exhibited moderate CCR5 antagonistic activity and had an acceptable pharmacokinetic profile in rats. Subsequent chemical modification was performed and compound (S)-5f possessing the (S)-configuration hydroxy group was found to be more active than the (R)-isomer. Replacement of the 1-benzoxepine ring with a 4-methylphenyl group by a 1-benzazepine ring with a 4-[2-(butoxy)ethoxy]phenyl group enhanced the activity in the binding assay. In addition, introduction of a 3-trifluoromethyl group on the phenyl group of the anilide moiety led to greatly increased activity in the HIV-1 envelope-mediated membrane fusion assay. In particular, compound (S)-5s showed the most potent CCR5 antagonistic activity (IC(50)=7.2 nM) and inhibitory effect (IC(50)=5.4 nM) in the fusion assay, together with good pharmacokinetic properties in rats.     

Tunnel electrode: Part II. Electron-transfer theory at an n-type semiconductor tunnel electrode

The formula for the cathodic tunnel current at an n-type semiconductor tunnel electrode was derived from the double adiabatic perturbation theory considering the vibration in the first coordination sphere. In the low-temperature limiting case, the apparent difference between the normal and the abnormal regions was observed in both the transfer coefficient α and the activation energy E* as a function of potential. It was concluded that the semiconductor tunnel electrode has advantageous characteristics for investigation of the electron-transfer mechanism at high overvoltage.     

Quasiadditivity and measure property of capacity and the tangential boundary behavior of harmonic functions

We show that if a set is dispersely decomposed into subsets, then the capacity of is comparable to the summation of the capacities of the subsets. From this fact it is derived that the Lebesgue measure of a certain expanded set is estimated by the capacity of . These properties hold for classical capacities, -capacities and energy capacities of general kernels. The estimation is applied to the boundary behavior of harmonic functions. We introduce a boundary thin set and show a fine limit type boundary behavior of harmonic functions. We show that a thin set does not meet essentially Nagel-Stein and Nagel-Rudin-Shapiro type approaching regions at almost all bounary points.

     

Axial chirality control of tropos BIPHEP-Rh complexes by chiral dienes: synergy effect in catalytic asymmetric hydrogenation

Diastereopure tropos Rh complexes bearing not only BIPHEP but also chiral dienes can be employed as highly enantioselective hydrogenation catalysts for an olefinic substrate.