Peroxycarbenium-mediated C-C bond formation: applications to the synthesis of hydroperoxides and peroxides

The Lewis acid-mediated reaction of alkene nucleophiles with peroxyacetals provides an effective route for the synthesis of homologated peroxides and hydroperoxides. In the presence of Lewis acids such as TiCl(4), SnCl(4), and trimethylsilyl triflate, peroxyacetals and peroxyketals undergo reaction with allyltrimethylsilane, silyl enol ethers, and silyl ketene acetals to afford homoallyl peroxides, 3-peroxyketones, and 3-peroxyalkanoates, respectively. Reactions of peroxyacetals are Lewis acid dependent; TiCl(4) promotes formation of ethers while SnCl(4) and trimethylsilyl triflate promote formation of peroxides. Lewis acid-promoted reactions of silylated hydroperoxyacetals furnish silylated hydroperoxides, which can be deprotected to homologated hydroperoxides. Hydroperoxyketals undergo Lewis acid-mediated allylation to furnish 1,2-dioxolanes via attack of hydroperoxide on the intermediate carbocation. Lewis acid-mediated cyclization of unsaturated peroxyacetals furnishes 1,2-dioxanes, 1,2-dioxepanes, and 1,2-dioxacanes through 6-endo/exo, 7-endo/endo, and 8-endo/endo pathways. The corresponding reactions involving 6-endo/endo and 5-endo/exo pathways were unsuccessful.     

New Mab CB.Hep-1 Purification Process Eliminates the Need for Pre-Chromatographic Purification. Stability Demonstrated Over 100 Purification Cycles

This investigation sought to discover whether purification of monoclonal antibody CB.Hep-1 in ascitic fluid is possible by protein A–Sepharose affinity chromatography, for 100 runs, without pre-purification steps. Results showed that direct application of ascitic fluid to protein A–Sepharose increased monoclonal antibody recovery by 27% compared with the traditional process (control) after 100 runs. The purity of the monoclonal antibody was >95% and the cost of the purification was 15% less than that of the control process. In conclusion, monoclonal antibody CB.Hep-1 in ascitic fluid can be purified by chromatography on protein A–Sepharose, for 100 purification cycles, without the need for pre-purification steps.     

Sensitive and Profitable Electrochemical Detection of Uric Acid in the Presence of Dopamine with a Novel Carbon Paste Electrode Decorated with a Copper(II) Complex

A new microcomposite with copper(II) complex and carbon paste (Cu_C/CPE) was developed to determine the uric acid (UA) content in the presence of dopamine (DP) and was characterized via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and energy dispersive spectroscopy (EDS). The results showed high selectivity for UA compared with DP because the anodic peak currents for DP were near those of a CPE without Cu_c and were considerably increased for UA. The UA and DP increases were 86.9 % and 14.3 %, respectively, according to CV and 96.6 % and 25.5 %, respectively, according to square wave voltammetry (SWV) with the Cu_C/CPE. Moreover, the anodic peak separation for UA and DP was 0.17 V. With optimal parameters (pH, 3.3; adsorption time(t_ADS), 30 s;adsorption potential (E_ADS)_, 0.10 V), the anodic peak currents for UA were proportional to concentrations between 1.6 and 14.4 μmol L^?1 using standard solutions with UA concentrations ranging from 8.0–40.5 μmol L^?1 and real samples. The UA detection limit was 0.13 μmol L^?1. The new sensor was used to determine the UA contentin human urine samples, and the method was checked with a urine chemistry control from Bio‐Rad based on human urine spiked with quantities of UA and showed a recovery between 84 % and 106 % at concentrations below 10.0 μmol L^?1.     

Synthesis and characterization of boron silicon oxycarbide glass fibers

Boron silicon oxycarbide fiber mats have been obtained through pyrolysis in inert atmosphere of sol–gel derived hybrid materials. The characterization of the preceramic hybrid fibers and the pyrolysis process reveals different boron incorporation depending on the composition. The ceramic conversion involves a series of reactions governed by the presence of the mixed bonds that implies larger phase segregation and higher graphite nanodomain size with the decrease of the number of borosiloxane bridges in the preceramic material. The formation of a mixed structure, where both Si and B are taking part on the ceramic network occurs with the excess of B that precipitates as boric acid in the surface of the fibers. These precipitates can cause pores in the surface of the pyrolyzed fiber.