One-Pot Tandem Coupling Method for the Short-Step Formal Synthesis of Riccardin C.

One-pot reactions reduce reagent amounts and circumvent process treatments, such as work-up and purifications in multi-step reactions. In this study, we achieved the formal total synthesis of riccardin C through a one-pot reaction by simultaneously linking four units through two Sonogashira coupling reactions and one Suzuki coupling reaction, followed by reduction and deprotection. Thus, this one-pot method comprised five steps and did not require the purification of intermediate reaction mixtures, which saves resources, such as reagents and solvents, and expedites the work process.

Practical method for hydroxyl-group protection using strontium metal and readily available silyl chlorides.

We have found that the etherification of silyl-protected secondary alcohols proceeds smoothly in the presence of strontium metal using silyl chloride instead of the expensive, yet more reactive, and commonly used silyl triflate. The reaction occurred almost completely with various alcohols.

Recovering metals from aqueous solutions by biosorption onto phosphorylated dry baker's yeast.

Biosorption is a cost-effective and simple technique for removing heavy metals and rare earth elements from aqueous solution. Here, metals were recovered from aqueous solutions using phosphorylated dry baker's yeast cells. The cells were phosphorylated using cyclo-triphosphate, Na3P3O9. The total P content of the phosphorylated cells was ~1.0 mmol/g dry cell weight (DCW). The zeta potential of the phosphorylated cells was -45 mV, two times higher than for the non-phosphorylated cells. The strong negative charges of the phosphorylated cells allowed the cells to adsorb heavy metal ions such as Cd2+, Cu2+, Pb2+, and Zn2+, the adsorption capacities of which reached ~1.0 mmol/g DCW. This adsorption capacity was the highest level found in the previous studies using yeast dead biomass. The adsorbed metal ions were easily desorbed in 0.1 M HCl. The phosphorylated cells also adsorbed rare earth ions including Ce3+, Dy3+, Gd3+, La3+, Nd3+, Y3+, and Yb3+ with high efficiency. Furthermore, the phosphorylated yeast cells selectively adsorbed the rare earth ions (Nd3+ and Yb3+) from a solution containing heavy metals and rare earth ions because trivalent positively charged ions were adsorbed preferentially over divalent ions. Thus, phosphorylated yeast cells therefore have great potential for use as novel bioadsorbents. It is also expected that this technique can be applied to many microbial materials as well as yeast.

Yttrium decreases the intracellular Zn2+ concentration in rat thymocytes by attenuating a temperature-sensitive Zn2+ influx.

Yttrium is used in the production of various electronic devices because the alloy it contains enhances or modifies the properties of other elements. In order to study the cytotoxic action of yttrium, the effect of yttrium chloride (YCl(3)) on the intracellular Zn(2+) level was examined in rat thymocytes using a flow cytometer with FluoZin-3-AM and propidium iodide. The application of YCl(3) significantly decreased the intensity of the FluoZin-3 fluorescence, suggesting a decrease in the intracellular Zn(2+) level or quenching of the FluoZin-3 fluorescence by Y(3+). However, since Y(3+) did not attenuate the FluoZin-3 fluorescence under cell-free conditions, the latter suggestion was ruled out. Rat thymocytes possess a temperature-sensitive membrane pathway that carries Zn(2+) into the cells. The application of YCl(3) attenuated the FluoZin-3 fluorescence augmented by externally applied ZnCl(2) in a concentration-dependent manner. This suggested that Y(3+) inhibited the Zn(2+) influx, resulting in the decrease in the intracellular Zn(2+) level. Yttrium may induce dyshomeostasis of intracellular Zn(2+), leading to some cytotoxic actions.

Some characteristics of membrane Cd²+ transport in rat thymocytes: an analysis using Fluo-3.

Although cadmium-induced apoptosis of lymphocytes is one of common features in the immunotoxicity of cadmium, the membrane pathway for intracellular cadmium accumulation is not fully elucidated. To characterize membrane Cd(2+) transport of rat thymocytes, the change in intracellular Cd(2+) concentration under various conditions was examined by the use of Fluo-3, a fluorescent probe for monitoring the change in intracellular concentration of divalent metal cations. The membrane Cd(2+) transport was estimated by the augmentation of Fluo-3 fluorescence induced by bath application of CdCl(2). Lowering temperature strongly suppressed the augmentation of Fluo-3 fluorescence by CdCl(2), suggesting that the metabolic process can be involved in membrane Cd(2+) transport. External acidification (decreasing pH) and membrane depolarization by adding KCl attenuated the augmentation, indicating the requirement of electrochemical driving force for membrane Cd(2+) transport into the cells. Bath application of CaCl(2) and ZnCl(2) equally decreased the augmentation, suggesting their competition with Cd(2+) at the membrane transport. The augmentation by CdCl(2) was lesser in the cells treated with N-ethylmaleimide inducing chemical depletion of cellular thiols. The result suggests the contribution of sulfhydryl groups to membrane Cd(2+) transport. Taken together, it is suggested that the cells possess a temperature-sensitive membrane Cd(2+) pathway, driven by electrochemical gradient of Cd(2+) and transmembrane potential, with competitive binding site. Based on the characteristics described above, it is unlikely that the membrane Cd(2+) transport in rat thymocytes is attributed to a single transport system although it has characteristics that are similar to those of divalent cation transporter 1.

A highly efficient carbon-carbon bond formation reaction via nucleophilic addition to N-alkylaldimines without acids or metallic species.

A nucleophilic addition reaction to N-methylaldimines without acid or metal species is described. A novel reagent, dicyanomethyl acetate, is used as a nucleophile to give alpha-(N-methyl-N-acetyl)amino acid methyl esters in excellent yield.

Cytometric analysis of adverse action of diphenyl ditelluride on rat thymocytes: cell shrinkage as a cytotoxic parameter.

Despite the growing use of organotellurium compounds in the chemical and biomedical fields, there has been no great concern about their toxicity until now. To test the possibility that diphenyl ditelluride (DPDT) and tellurium chloride (TeCl2), organic and inorganic tellurium compounds, may exert adverse action on mammals, their effects on rat thymocytes were examined under in vitro conditions using a flow cytometer with fluorescent probes. Incubation of thymocytes with DPDT at 300 nM or more for 24 h significantly increased the populations of shrunken cells and of cells with hypodiploidal DNA. Z-VAD-FMK, a paninhibitor of caspases, greatly suppressed the DPDT-induced increase in the hypodiploidal cell population, suggesting the involvement of caspase activation in DPDT toxicity. Hence, it is possible that DPDT would increase the population of thymocytes undergoing apoptosis if the blood concentration in mammals reached at least 300 nM or more. TeCl2 was much less potent than DPDT in increasing the population of hypodiploidal cells.

A convenient procedure for bismuth-mediated Barbier-type allylation of aldehydes in water containing fluoride ions.

A new and convenient procedure for synthesis of homoallylic alcohols in generally good to excellent yields has been developed. The bismuth-mediated Barbier-type allylation of aldehydes (aromatic, aliphatic, alicyclic and heterocyclic) with allyl bromide has been carried out smoothly in water in the presence of fluoride ions.