Formation of keto-carbeniums from 1,2,2-triarylacenaphthen-1-ols by breaking a long CC bond: unusual alcohol protonolysis accompanied by formal hydride abstraction

Oxidation of 1,2,2-tris(4-dimethylaminophenyl)- and 2,2-bis(4-dimethylaminophenyl)-1-phenylacenaphthen-1-ols 1a,b with I₂ induced the C₁C₂ bond fission to give 8-aroylnaphthalen-1-yl-bis(4-dimethylaminophenyl)carbenium derivatives 2a,b⁺, the intramolecular Lewis acid-base pairs. Treatment of 1 with HBF₄ did not induce the expected COH bond heterolysis but caused fission of COH and C₁C₂ bonds to give exactly the same carbenium 2⁺.     

Aggregate formation in oil and adsorption at oil/water interface: thermodynamics and its application to the oleyl alcohol system

The thermodynamic equations for examining aggregate formation in an oil phase and adsorption at the oil/water interface of a nonionic solute were derived. The total differentials of chemical potentials of species and the oil/water interfacial tension were expressed as functions of temperature, pressure, and the total concentration of solute in the oil phase after explicit consideration of aggregate formation. The partial derivatives of the chemical potentials and the interfacial tension with respect to the independent variables were found to provide the thermodynamic quantities of aggregate formation and adsorption from oil phase to the interface by introducing the concept of an ideally dilute associated solution. These equations were applied to the cyclohexane solution of oleyl alcohol/water system, and the adsorption and aggregate formation was examined.     

Preparation, properties, and X-ray structures of 5,5-bi(8-aminoquinoxalyl)s: novel Wurster-type electron donors with a heterobiaryl skeleton

The title electron donors were prepared by the double condensation reactions of 2,2^′,3,3^′-tetraamino-4,4^′-bis(1-pyrrolidinyl)biphenyl with 1,2-diketones. They adopt twisted conformations in crystal, yet the reversible two-stage one-electron oxidation process suggests the planar geometries for the oxidized species. Depending on the nature of substituents on the pyrazine ring, this π-system can be endowed additional features such as chiroptical properties or metal coordination ability.     

Factors affecting sulfisoxazole transport through excised rat skin during iontophoresis

Permeation of sulfisoxazole (SIX) across the excised rat skin were studied using two chamber cell with four electrodes, under three successive experimental conditions: without current for 3 h (treatment I), with current for 4 h (treatment II) and without current for 3 h (treatment III). Transport of SIX was significantly increased by iontophoresis. The enhancement ratio of SIX flux were reasonably predicted by Goldman's equation. There was no significant difference (p less than 0.05) between the flux in treatment I and treatment III. On the basis of the flux reversibility, it was concluded that skin alteration did not occur when the applied electric potential was below 5.025 V. Although a prominent current-induced volume flow (from the anodal side to the cathodal side) was observed during current exposure, SIX flux was not influenced by the volume flow. The flux enhancement of SIX was mainly dependent on transdermal potential difference.     

Facile distinction of neutral and acidic tetraether lipids in archaea membrane by halogen atom adduct ions in electrospray ionization mass spectrometry

Calditocaldarchaeol (neutral tetraether lipid) from Sulfolobus acidocaldarius (acidothermophilic archaea) and intact total lipid from the thermoacidophilic archaea Sulfolobus sp. was examined by electrospray ionization time-of-flight mass spectrometry in the negative-ion mode using high resolution. When the sample was injected as a solution in a 3:1 mixture of methanol (MeOH) and chloroform (CHCl(3)) using an infusion system, the total ether lipid afforded molecular-related ions as [M - H](-) for acidic polar lipids containing a phosphoric or sulfuric group, and as [M + Cl](-) ion for neutral glycolipids. The attachment of chloride was confirmed by the observation of [M + Br](-) ion, instead of [M + Cl](-) ion, when a 3:1 mixture of MeOH and CHBr(3) was used in place of MeOH-CHCl(3) as the solvent. The composition of tetraether neutral glycolipids that are different from each other only in the number of five-membered rings in the isoprenoid chain was determined on the basis of the isotope-resolved mass spectrum of [M + Cl](-) ions. As for acidic tetraether lipids, molecular-related ions [M - H](-)) were not observed when the 3:1 MeOH-CHBr(3) mixture was used as the solvent. These results together afforded a facile method of distinguishing neutral from acidic tetraether lipids in intact total lipids of acidothermophilic archaea. This method was applied to determine the difference of the number of five-membered rings in isoprenyl chains of neutral tetraether glycolipids yielded by the Sulfolobus sp. grown at different temperatures. Discrimination of neutral tetraether glycolipids from acidic tetraether lipids in the total lipids obtained from Thermoplasma sp. was also achieved by this method.     

Catalytically active mu-Oxodiiron(IV) oxidants from Iron(III) and dioxygen

The reaction between an Fe(III) complex and O(2) to afford a stable catalytically active diiron(IV)-mu-oxo compound is described. Phosphonium salts of orange five-coordinated Fe(III)-TAML complexes with an axial aqua ligand ([PPh(4)]1-H(2)O, tetraamidato macrocyclic Fe(III) species derived from 3,3,6,6,9,9-hexamethyl-3,4,8,9-tetrahydro-1H-1,4,8,11-benzotetraazacyclotridecine-2,5,7,10(6H,11H)-tetraone) react rapidly with O(2) in CH(2)Cl(2) or other weakly coordinating solvents to produce black mu-oxo-bridged diiron(IV) complexes, 2, in high yields. Complexes 2 have been characterized by X-ray crystallography (2 cases), microanalytical data, mass spectrometry, UV/Vis, Mossbauer, and (1)H NMR spectroscopies. Mossbauer data show that the diamagnetic Fe-O-Fe unit contains antiferromagnetically coupled S = 1 Fe(IV) sites; diamagnetic (1)H NMR spectra are observed. The oxidation of PPh(3) to OPPh(3) by 2 was confirmed by UV/Vis and GC-MS. Labeling experiments with (18)O(2) and H(2)(18)O established that the bridging oxygen atom of 2 derives from O(2). Complexes 2 catalyze the selective oxidation of benzylic alcohols into the corresponding aldehydes and bleach rapidly organic dyes, such as Orange II in MeCN-H(2)O mixtures; reactivity evidence suggests that free radical autoxidation is not involved. This work highlights a promising development for the advancement of green oxidation technology, as O(2) is an abundant, clean, and inexpensive oxidizing agent.     

Pyrazino-tetracyanonaphthoquinodimethanes: sterically deformed electron acceptors affording zwitterionic radicals

The X-ray analyses of the title electron acceptors (1) revealed their butterfly-shaped deformed geometry, which is not affected by the pyridyl group attached at 2-position of the pyrazino-TCNNQ skeleton. Small differences between the first and second reduction potentials (ca. 0.1 V) in pyrazino-TCNNQs show that their anion radicals (1⁻) are prone to disproportionate into the neutral (1) and dianionic (1²⁻) species. The thermodynamically unstable anion radical species based on the pyrazino-TCNNQ skeleton could be isolated as inner salts upon electrochemical reduction of the derivatives having an N-methylpyridinium moiety at 2-position (2⁺). The zwitterionic open-shell species (2) constitute a novel class of radicals that exhibit semiconducting behavior as a single component thanks to the high electrochemical amphotericity.     

Sequence-specific gene silencing in mammalian cells by alkylating pyrrole-imidazole polyamides

Gene silencing was examined by sequence-specific alkylation of DNA by N-methylpyrrole (Py)-N-methylimidazole (Im) hairpin polyamides. Polyamides ImImPyPygammaImImPyLDu86 (A) and ImImPyPygammaImPyPyLDu86 (B) selectively alkylated the coding regions of the renilla and firefly luciferases, respectively, according to the base pair recognition rule of Py-Im polyamides. Two different plasmids, encoding renilla luciferase and firefly luciferase, were used as vectors to examine the effect of alkylation on gene silencing. Transfection of the alkylated luciferase vectors-by polyamide A or B-into HeLa, 293, and NIH3T3 cells demonstrated that these sequence-specific DNA alkylations lead to selective silencing of gene expression. Next, the vectors were cotransfected into HeLa cells and the cells were treated with polyamide A or B. Selective reduction of luciferase activities was caused by both polyamides. On the basis of this sequence-specific alkylation and gene silencing activity, these alkylating Py-Im polyamides thus have potential as antitumor drugs to target specific gene expression in human cells.