Chemical compositional separation of styrene-methyl methacrylate copolymers using high-performance liquid chromatography with liquefied carbon dioxide as eluent

Chromatographic separation of styrene-methyl methacrylate (MMA) copolymers depending on the chemical composition was studied using liquefied carbon dioxide as an adsorption promoting solvent, and tetrahydrofuran, chloroform containing ethanol as a desorption promoting solvent in the mobile phase and the column packed non-bonded silica gel by a solvent gradient method. With the increase of MMA content, the elution was retarded indicating that the typical normal-phase type of adsorption occurred. The effects of type of desorption solvents, molecular mass of sample, and column temperature on the elution were investigated.     

Physical and Chemical Properties of Four-Membered Bis(triphenylphosphane)platinum(II) Sulfenato Thiolato Complexes

The reaction of isolable dithiirane 1-oxides with (Ph 3 P) 2 Pt( m 2 -C 2 H 4 ) provided the title complexes in high yields. 31 P NMR spectroscopy of the phosphine ligands of the complexes and x-ray crystallographic analysis of a complex were reported.     

Synthesis of green organogelators with a sulfide linkage via solvent-free Michael addition: soft templates for the preparation of size-controlled gold nanoparticles

Green organogelators with a sulfide linkage and free amino groups were synthesized via phase transfer catalysis using a N-benzylcinchonidinium bromide catalyst. Their self-assemblies in various common solvents were examined. These compounds exhibit high gelation ability especially in aromatic and highly polar solvents with a low critical gelation of 0.1 wt %. The organogels were analyzed by ¹H nuclear magnetic resonance (¹H NMR) and Fourier transfer-infrared spectroscopies (FT-IR), and their phase transition temperatures were determined by differential scanning calorimetry. The homogeneity of the gel networks was examined by field emission scanning electron microscopy and transmission electron microscopy (TEM). A lamellar structure was also confirmed by X-ray diffraction analysis. The organogels were employed as soft-templates for the in situ generation of stable gold nanoparticles dispersed in the gel matrix, and the resulting GNP dispersions were studied by ¹H NMR and UV–vis absorption. Transmission electron microscopy showed that GNPs assemble into a thin membrane-like structure.     

Chiral Dinuclear EuIII,TbIII, and YIII Complexes Supported by P-Stereogenic Linear Tetraphosphine Tetraoxide

A P-stereogenic linear tetraphosphine tetraoxide, (R,R)- or (S,S)-dpmppm(=O)₄, was synthesized to prepare C₂ dinuclear M(hfa)₃ complexes (M=Eu, Tb, Y) as the first example of lanthanide(III) complexes with P-chiral multidentate phosphine oxides. The mononuclear M(hfa)₃ complexes (M=Eu, Y) with a P-chiral diphosphine dioxide, tpdpb(=O)₂, were also prepared, and comparison of their photophysical properties for the Eu^III complexes revealed that significant chiral induction from the P-chiral centers arises on the achiral M(hfa)₃ units through intramolecular π-π stacking constraint in the dinuclear system.     

Novel synthesis of zerumbone-pendant derivatives and their biological activity

Zerumbone 1, having powerful latent reactivity and containing two conjugated double bonds and a double conjugated carbonyl group is the major component of the essential oil of wild ginger, Zingiber zerumbet Smith. The conjugation system plays an important role in the expression of biological activity. N-Bromosuccinimide (NBS) reaction of 1 gave high reactive intermediate 2 with an exo-methylene group, which was obtained from 1 quantitatively. Treatment of 2 with nucleophiles gave various zerumbone-pendant derivatives, including C–H, C–O, C–N, and C–C bond formation, maintaining the conjugation system through S_N2′-type reaction. Almost all zerumbone-pendant derivatives showed a good value of IC₅₀ against the suppressive effect of NO generation. Among them, amine derivative 5, binding with 2 mol of zerumbone, showed the strongest activity (IC₅₀: 0.24 μM).     

FUNCTIONS OF LIPIDS ON HUMAN SKIN

In order to clarify the roles of lipids in the water-holding property of stratum corneum, the forearm skin of healthy male volunteers was treated with acetone/ether (1/1) or sodium dodecyl sulfate (5%) for 1-30 min. A prolonged treatment period of 5-30 min produced a chapped and scaly appearance of the stratum corneum without any inflammatory reactions. Under these conditions, there was a marked decrease in the water-holding capacity of the stratum corneum accompanied by a selective loss of stratum corneum lipids such as cholesterol, cholesterol esters, and sphingolipids. Two daily applications of the isolated stratum corneum lipids to experimentally induced dry skins caused a significant increase of conductance, accompanied by a marked improvement in the level of scaling. Meanwhile, the isolated sebaceous lipids exhibited no significant recovery in both the conductance value and the scaling. Out of chroma-tographically separated fractions of the stratum corneum lipids, topical applications of ceramide fraction induced the highest increase in the conductance value. Topical applications of synthesized pseudo-ceramides also showed a significant recovery of the water-retaining properties accompanied by an improvement in the scaling only when the polar group has an amide bond in the major linkage. Analysis of the alkyl chain structures has revealed that a structural requirement for the recovery of the water retaining capacity is the presence of saturated-straight alkyl chains, not unsaturated or branched alkyl chains. These structural characteristics required for water-retaining function also paralleled their capacity to form multiconcentric lamellae vesicles in vitro which is also capable of acquiring bound water as shown by DSC thermograms. The present study suggests that ceramides with relatively shorter alkyl chain length serve as a water modulator in the multi-lipid bilayers through the stratum corneum.     

Chirality Induction by Formation of Assembled Structures Based on Anion‐Responsive π‐Conjugated Molecules

Anion‐responsive π‐conjugated compounds having chiral alkyl chains were synthesized. Circular dichroism (CD) and circularly polarized luminescence (CPL) were observed in the solution‐state assemblies of the chiral anion receptors and those of their anion complexes as salts of a planar triazatriangulenium cation. The CD and CPL spectral patterns of the ion‐pair‐based assemblies were completely opposite to those of the anion‐free assemblies, and this suggests that anion binding and subsequent ion pairing change the chirality of the assembly modes.     

Chiral Photoresponsive Tetrathiazoles That Provide Snapshots of Folding States

Herein, we designed chiral photoresponsive tetra(2‐phenylthiazole)s, which induce a diastereoselective 6π‐electrocyclization reaction in a helically folded structure to freeze the conformational interconversions. The folding conformation with one helical turn of tetra(2‐phenylthiazole)s was supported by multiple intramolecular noncovalent interactions including vicinal S???N interheteroatom interactions and CH–π and π–π stacking interactions between nonadjacent units, as found in X‐ray crystal structures as well as quantum chemical calculations. The introduction of a chiral group at both ends of tetra(2‐phenylthiazole) dictates the preferential folding into a one‐handed helix conformation by the simultaneous operation of S???O and multiple CH–π interactions that involve the chiral end groups. Since the tetra(2‐phenylthiazole)s possess two equivalent photoreactive 6π‐electron systems and the folded conformation is suitable for photoinduced electrocyclization reaction, they undergo a photocyclization reaction in a stereoselective manner to memorize the chirality of the helix in a resulting diastereomeric closed form.