Rotational Spectra of XeH and Its Isotopic Species

Frequencies of rotational transitions of XeH⁺ and its isotopic species were measured in the 1–5 THz region with a highprecision far-infrared spectrometer using a tunable radiation source. Measured frequencies were analyzed together with previous microwave and infrared measurements to refine mass-independent Dunham parameters.     

SCOTfluors: Small,Conjugatable, Orthogonal,and Tunable Fluorophores for In Vivo Imaging of Cell Metabolism

The transport and trafficking of metabolites are critical for the correct functioning of live cells. However, in situ metabolic imaging studies are hampered by the lack of fluorescent chemical structures that allow direct monitoring of small metabolites under physiological conditions with high spatial and temporal resolution. Herein, we describe SCOTfluors as novel small‐sized multi‐colored fluorophores for real‐time tracking of essential metabolites in live cells and in vivo and for the acquisition of metabolic profiles from human cancer cells of variable origin.     

Coumarins with an unprecedented tetracyclic skeleton and coumarin dimers from chemically engineered extracts of a marine-derived fungus

The unprecedented tetracyclic coumarin derivatives 1 and 2 and the coumarin dimers 3–5 were isolated from chemically engineered extracts (coumarin dimerization of natural extract) of the marine-derived fungus Eurotium rubrum. The structures of these compounds were established using NMR, MS and IR methods. The absolute configuration of 1 was determined by ECD calculations. The unprecedented tetracyclic coumarin skeleton was generated by domino-Knoevenagel-Diels-Alder reactions. Compounds 1–5 showed tyrosinase inhibitory activity (IC₅₀?=?1.7, 1.2, 4.9, 1.8 and 2.9?μM, respectively). The isolated coumarin derivatives 1–5 were not observed by HPLC analysis in crude extracts of E. rubrum, suggesting that chemically engineered extract generated these new coumarin derivatives with tyrosinase inhibitory activity.     

Chemical release control: Sulfonate esters from perfume and herbicide alcohols and p-styrenesulfonyl chloride

p-Styrenesulfonate esters of primary and secondary perfume alcohols and phenols, including citronellol, 1-menthol, borneol, β-phenethyl alcohol, eugenol, p-anisyl alcohol, cinnamyl alcohol, and geraniol, and herbicide alcohols such as 2,4-dichloro- and 2,4,5-trichlorophenoxy-ethanols were synthesized using p-styrenesulfonyl chloride in the presence of bases such as pyridine, triethylamine, sodium hydrogen carbonate, and sodium hydride. The hydrolytic behavior of sulfonate ester monomers and their copolymers with N-vinyl-2-pyrrolidone to liberate perfume and herbicide alcohols was structure-dependent, thereby affording chemical release control.     

Comparison of temperature,pressure and isotope effects on the proton jump between the hydroxide and oxonium ion

The limiting molar conductances ° of potassium deuteroxide KOD in D₂O and potassium hydroxide KOH in H₂O were determined at 5 and 45°C as a function of pressure to clarify the difference in the temperature, pressure and isotope effects on the proton jump between an OD^– (OH^–) and a D₃O⁺ (H₃O⁺) ion. The excess conductances of the OD^– ion in D₂O and the OH^– ion in H₂O, _E ⁰ (OD^-) and _E ⁰ (OH^-), increase with increasing temperature and pressure as in the case of the excess deuteron and proton conductances, _E ⁰ (D⁺) and _E ⁰ (H⁺). However, the temperature effect on the excess conductance is larger for the OD^–(OH^–) ion than for the D₃O⁺ (H₃O⁺) ion but the pressure effect is much smaller for the OD^– (OH^–) ion than for the D₃O⁺ (H₃O⁺) ion. These findings are correlated with larger activation energies and less negative activation volumes found for the OD^– (OH^–) ion than for the D₃O⁺ (H₃O⁺) ion. Concerning the isotope effect, the value of _E ⁰ (OH^-)/ _E ⁰ (OD^-) deviates considerably from at each temperature and pressure in contrast with that of _E ⁰ (H⁺)/ _E ⁰ (D⁺), although both of them decrease with increasing temperature and pressure. These results are discussed mainly in terms of the difference in repulsive force between the OD^– (OH^–) or the D₃O⁺ (H₃O⁺) ion and the adjacent water molecule, the difference in strength of hydrogen bonds in D₂O and H₂O, and their variations with temperature, pressure, and isotope.     

Chemo-enzymatic short-step total synthesis of symbioramide

A concise synthesis of symbioramide, a marine-origin ceramide from a common starting material, methyl (±)-trans-2,3-epoxyoctadecanoate, in a convergent manner was achieved. The key step is the direct lipase-catalyzed coupling reaction between methyl (2R,3E)-2-hydroxy-3-octadecenoate and non-protected (±)-erythro-dihydrosphingosine, giving natural (2S,3R,2′R)-symbioramide and its (2R,3S,2′R)-isomer in 38% and 37% yield, respectively. The optically active β,γ-unsaturated α-hydroxyester was prepared by Mg(ClO₄)₂-mediated isomerization of epoxide and the subsequent lipase PS-catalyzed kinetic resolution.     

Recyclable catalyst for conversion of carbon dioxide into formate attributable to an oxyanion on the catalyst ligand

The catalyst recycling in the conversion of CO2 into formate using the iridium complex with 4,7-dihydroxy-1,10-phenanthroline as a catalyst precursor is described. The catalyst precursor was dissolved in an aqueous KOH solution under CO2 pressure prior to the reaction, but was precipitated spontaneously at the end of the reaction. The acidification by the generation of formate caused the transformation from the water-soluble deprotonated form into the water-insoluble protonated form. When the reaction was carried out at 60 degrees C for 20 h using 0.1 M KOH solution under 6 MPa of H2:CO2 (1:1), the catalyst precursor was precipitated spontaneously and the added KOH was consumed completely. The catalyst was recovered by filtration, and the product was obtained by the evaporation of the filtrate. Iridium leaching into the filtrate was found to be 0.11 ppm (<2% of the loaded Ir). The recovered catalyst retained high catalytic activity for four cycles. Consequently, the CO2 conversion using the complex is an environmentally benign process, whose significant features are as follows: (i) catalyst recycling by self-precipitation/filtration, (ii) waste-free process, (iii) the easy isolation of the product, (iv) high efficiency under relatively mild conditions, and (v) aqueous catalysis without the use of organic materials. Furthermore, we have demonstrated the significant roles of the oxyanion generated from the acidic phenolic hydroxyl on the catalyst ligand, which are the catalyst recovery by acid-base equilibrium, as well as the water-solubility by its polarity and the catalyst activation by its electron-donating ability.     

High sensitivity and broad dynamic range infrared multiphoton dissociation for a quadrupole ion trap

Dynamic control of bath gas pressure in a quadrupole ion trap (QIT) achieved high sensitivity and broad dynamic range infrared multiphoton dissociation (IRMPD). Conventional IRMPD is not sensitive because the bath gas pressure in the QIT needs to be kept at less than 1 mTorr for an effective dissociation, whereas the pressure should be about 20 mTorr for maximum trapping efficiency during ion accumulation. By switching the bath gas pressure between about 20 mTorr during the ion accumulation period and less than 0.6 mTorr during the IRMPD period, it was possible to achieve both maximum trapping efficiency and effective IRMPD. An optimized method for gas introduction enables the trapping efficiency to remain constant during the accumulation period, which permits a broad dynamic range measurement.