Environmentally responsive molecular baskets: unimolecular mimics of both micelles and reversed micelles

[structure: see text] When four facially amphiphilic cholate derivatives are attached to a tetraaminocalixarene scaffold, the resulting molecule responds to environmental changes by rotation of the cholate units. In polar solvents, the molecule adopts a micellelike conformation with the hydrophilic alpha-faces of the cholates pointing outward. In nonpolar solvents, it turns inside out, assuming a reversed micellelike conformation with the hydrophobic beta-faces pointing outward. Switching between the two conformations is driven by solvophobic interactions and is fully reversible.     

Adsorption and isotope effects by ion exchange with aqueous-2-aminomethyl-18-crown-6 bonded merrifield resin

Magnesium isotopes effects were investigated by chemical ion exchange using synthesized 2-aminomethyl-18-crown-6 (AM18C6) bonded Merrifield peptide resin. It was found that separation factors larger those reported previously were obtained, and the hydration and isotope mass effects are more significant than that of the complexation. The capacity of the crown ion exchanger was 2.3 meq/g dry resin. The adsorption capacity of the resin for magnesium ion was 26.8 mg/g dry resin at pH 7. The heavier isotopes of magnesium were enriched in the solution phase, while the lighter isotopes were enriched in the resin phase. The separation factors of (24)Mg-(25)Mg, (24)Mg-(26)Mg, and (25)Mg-(26)Mg were 1.0085, 1.0162, and 1.0081, respectively.     

Magnesium isotope separation by ion exchange using hydrous manganese(IV) oxide

The magnesium isotope effects were investigated by chemical ion exchange with a hydrous manganese(IV) oxide. The capacity of manganese(IV) oxide was 0.5 meq g(-1). The distribution coefficient of magnesium ions on the MnO(2) was determined by a batch method. The heavier isotopes of magnesium were enriched in the solution phase, while the lighter isotopes were enriched in the hydrous MnO(2) phase. The separation factor was determined according to the method of Glueckauf from the elution curve and isotopic assays. The separation factors of (24)Mg(2+)-(25)Mg(2+), (24)Mg(2+)-(26)Mg(2+), and (25)Mg(2+)-(26)Mg(2+) isotope pair fractionations were 1.011, 1.021, and 1.011, respectively.     

Fenofibrate regulates obesity and lipid metabolism with sexual dimorphism

To determine whether the PPARalpha agonist fenofibrate regulates obesity and lipid metabolism with sexual dimorphism, we examined the effects of fenofibrate on body weight, white adipose tissue (WAT) mass, circulating lipids, and the expression of PPARalpha target genes in both sexes of high fat diet-fed C57BL/6J mice. Both sexes of mice fed a high-fat diet for 14 weeks exhibited increases in body weight, visceral WAT mass, as well as serum triglycerides and cholesterol, although these effects were more pronounced among males. Feeding a high fat diet supplemented with fenofibrate (0.05% w/w) reduced all of these effects significantly in males except serum cholesterol level. Females on a fenofibrate-enriched high fat diet had reduced serum triglyceride levels, albeit to a smaller extent compared to males, but did not exhibit decreases in body weight, WAT mass, and serum cholesterol. Fenofibrate treatment resulted in hepatic induction of PPARalpha target genes encoding enzymes for fatty acid beta-oxidation, the magnitudes of which were much higher in males compared to females, as evidenced by results for acyl-CoA oxidase, a first enzyme of the beta-oxidation system. These results suggest that observed sexually dimorphic effects on body weight, WAT mass and serum lipids by fenofibrate may involve sexually related elements in the differential activation of PPARalpha.     

Asymmetric addition of diethylzinc to aromatic aldehydes by chiral ferrocene-based catalysts

A series of chiral C₁- and C₂-symmetric ferrocenyl Schiff bases (1a-c), ferrocenyl aminoalcohols (2a), ferrocenylphosphinamides (2b-c), 1,1′-ferrocenyl-diol (3), and 1,1′-ferrocenyl-disulfonamide (4) were prepared and employed as base catalysts or as ligand for titanium(IV) complexes in the asymmetric addition of diethylzinc to aromatic aldehydes. High enantioselectivity up to almost 100% ee was achieved for the alkylation of benzaldehyde and p-methoxybenzaldehyde with 1 or 3. In contrast, however, the β-aminoalcohol (2a) and phosphinamides (2b and c) that are ubiquitous classes of base catalysts for this reaction proved inefficient in our hands, regardless of the types of substrates or reaction conditions. Comparative studies show that there exist various reaction parameters governing not only chemical yields but also optical yields. These include steric and electronic environment of the substrate, the solvent, the reaction temperature, and the nature of the ferrocene moieties.     

A Stereochemical Study of the Isomerization of Cyclopropyl Ethers to Allyl Ethers Catalyzed with Zinc Iodide

Optically active 1-alkoxybicyclo[4.1.0]heptane was converted using zinc iodide as a catalyst to 2-alkoxymethylidenecyclohexane without loss of optical purity. The mechanism of the isomerization was studied using a stereochemical analysis of the product and deuterium labeling experiments. The results indicated that the isomerization takes place through a stepwise mechanism that involves an attack of zinc iodide on the cyclopropane ring to cause ring opening, followed by an intramolecular 1,2-hydride shift with liberation of the zinc iodide.