Total synthesis of dehydroaltenusin

The first total synthesis of dehydroaltenusin, a natural enzyme inhibitor, is described. The key step involves Suzuki-coupling reaction of an aryl triflate prepared from 2,4,6-trihydroxybenzoic acid with a catechol-derived boronic acid or boronic ester. The synthetic product was evaluated as a potent inhibitor against eukaryotic DNA polymerase α and other DNA polymerases.     

Critical micelle concentrations and interaction parameters of aqueous binary surfactant:ionic surfactant mixtures

A relationship between the critical micelle concentration (CMC) and the surfactant's composition in the bulk phase that supercedes Rubingh's method is derived for aqueous mixtures of ionic surfactants by considering the interaction between a micellar ionic aggregate and the diffusion layer around it. To test this approach we measured the CMCs of solutions of cationic surfactant mixtures and also of alkylammonium dodecanesulfonate mixtures. In the absence of controlled concentration of the counterion, the CMCs do not fit Clint's equation, but CMCs measured at a constant counterion concentration fit it approximately. The interaction parameter in the theory of regular solutions is obtained from the relationship between the micellar and bulk compositions. The values of the interaction parameter and the concentration exponent change with the hydrophobicity of the counterion in mixtures of alkylammonium dodecanesulfonates. The micellar composition of dodecylammonium chloride and dodecyltrimethylammonium chloride mixtures depends very little on the counterion concentration. The interaction energy between the ammonium and trimethylammonium groups of the cationic surfactants is about -0.05kT on average and depends on the concentration of the counterion.     

Growth of ZnO crystal by self-flux method using Zn solvent

Zinc oxide (ZnO) single crystal was grown, for the first time, by the self-flux method using a high-purity zinc solvent saturated with oxygen. ZnO crystals were successfully grown in the solvent by moving a growing crystal slowly, at about 17 mm/day along a temperature gradient (1.5 °C/mm) in a furnace, from 1050 to 500 °C. Hexagonal single crystals 1–3 mm in length and 0.5–1 mm in thickness were obtained. Energy-dispersive X-ray diffraction, secondary ion mass spectrometry, and photoluminescence confirmed that the purity and crystallinity of the ZnO crystals grown in this work were high.     

Column switching high-performance liquid chromatography with two channels electrochemical detection for high-sensitive determination of isoflavones

Column switching HPLC with electrochemical detection (HPLC-ED), which consists of one pre-column and two electrochemical detectors subsequent to each analytical column, called HPLC-2ED, has been developed for determining isoflavones (daidzin, genistin, daidzein, and genistein) with high sensitivity. In the present HPLC-2ED, the eluted daidzin and genistin from the pre-column were separated on an analytical column using a methanol–water–phosphoric acid mixture (30:70:0.5) as the mobile phase (MP), and daidzein and genistein were separated on another analytical column using a methanol–water–phosphoric acid mixture (50:50:0.5). The way of the elute flow from the pre-column was changed by rotating the switching valve at 17 min. The difference in retention times of genistein between isocratic HPLC-ED and HPLC-2ED was 52.2 min. The detection limit (S/N = 3) per column injection (5 μL) of genistein was 0.5 pg. The sensitivity by the present method is superior to that of previously reported gradient HPLC-ED for the determination of isoflavones.     

Total Synthesis of (+)-Sch 725680: Inhibitor of Mammalian A-, B-, and Y-Family DNA Polymerases

The total synthesis of (+)-Sch 725680, a member of the hydrogenated azaphilone family, has been accomplished. The synthesis confirmed the absolute configuration and biological activities of the natural product. A key reaction to construct a hydrogenated azaphilone core skeleton is a Ti-mediated aldol reaction.     

Polymorphism of phenylpyruvic acid studied by IR, Raman and solid state C NMR spectroscopy

Polymorphs I and II of phenylpyruvic acid are obtained as mixtures of both crystal forms or relatively pure crystals, from different solvents. Polymorph I is more stable than polymorph II at room temperature. Spectral characteristics of these polymorphs are discussed on the basis of IR, Raman and solid state ¹³C NMR spectra. Also, the assignment of the IR features observed in the 1600–1700 cm⁻¹ region is re-investigated by referring to the spectra of heavy-atom substituted derivatives. It is suggested that the C=O stretching band is split by the crystal field for both polymorphs.     

Bulk superconducting phase with a full energy gap in the doped topological insulator Cu(x)Bi₂Se₃

The superconductivity recently found in the doped topological insulator Cu(x)Bi?Se? offers a great opportunity to search for a topological superconductor. We have successfully prepared a single-crystal sample with a large shielding fraction and measured the specific-heat anomaly associated with the superconductivity. The temperature dependence of the specific heat suggests a fully gapped, strong-coupling superconducting state, but the BCS theory is not in full agreement with the data, which hints at a possible unconventional pairing in Cu(x)Bi?Se?. Also, the evaluated effective mass of 2.6m(e) (m(e) is the free electron mass) points to a large mass enhancement in this material.     

Halovinylsulfones 4 . Synthesis and some reactions of 2-phenylsulfonyl-2-propenyl isothiocyanate

The title compound, isothiocyanate 2 , was obtained in good yield from the reaction of α-chloromethylvinyl-sulfone 1 with lead thiocyanate. The isothiocyanate 2 was reacted with aromatic amines to give 2-amino-5,6-dihydro-4H-1,3-thiazines 3 in good to moderate yields. The formation pathways are discussed.     

Effect of the Head Group of Surfactant on the Miscibility of Sodium Chloride and Surfactant in an Adsorbed Film and Micelle

The thermodynamic treatment of a surfactant mixture was applied to the mixture of sodium chloride, NaCl, with octyl methyl sulfoxide (OMS) and that with decyldimethylphosphine oxide (DePO). The surface tension of aqueous solutions of the mixtures was measured as a function of the total concentration and the composition of the mixtures at 298.15 K. The total surface densities of the mixtures and the composition of the adsorbed films and micelles were evaluated by applying thermodynamic equations to the expeimental results. It was found that the adsorbed film and micelle are almost composed of the surfactant and there is slight attractive interaction between the ions of NaCl and the head groups of OMS and DePO molecules in the adsorbed films and micelles. A difference in the miscibility of NaCl and surfactant was observed between the OMS and DePO systems and attributed to the difference in the hydration of the head group between OMS and DePO molecules. The comparison of these results with those of the mixtures of NaCl with tetraethylene glycol monooctyl ether (C(8)E(4)) and dodecylammonium chloride (DAC) indicated that the small difference in the miscibility in an adsorbed film and micelle among these nonionic surfactant systems arises from the difference in hydration and structure of the head groups and the large one between the nonionic surfactant and DAC systems results from electrostatic interactions between dodecylammonium and sodium ions. Copyright 2001 Academic Press.