PubMed · 13167025
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V L EINIS. [Bromine in function tests in tuberculosis].. https://pubmed.ncbi.nlm.nih.gov/13167025/
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Addition of solid Ca(OCl)(2) as the terminal oxidant in the TEMPO-mediated selective oxidation has the benefit of easier operation. A variety of partially protected saccharide derivatives (1a-l) have been successfully converted into the corresponding uronate derivatives, including disaccharide building blocks for GAG fragments and precursors to saponins. The beneficial effect of Aliquat 336 was also disclosed in the oxidation of certain substrates.
The Suzuki-Miyaura coupling of aryl chlorides and PhB(OH)(2) under biphasic conditions (DMSO/heptane) can be performed in almost quantitative yields over several cycles by means of polymeric Pd catalysts with soluble polyethylene glycol phase tags. Three sterically demanding and electron-rich phosphines 1-CH(2)Br,4-CH(2)P(1-Ad)(2)-C(6)H(4), and 2-PCy(2),2'-OH-biphenyl, and 2-PtBu(2),2'-OH-biphenyl were covalently bonded to 2000 Dalton MeOPEG-OH. The catalysts, which were formed in situ from Na(2)[PdCl(4)], the respective polymeric phosphine, KF/K(3)PO(4), and PhB(OH)(2), efficiently couple aryl chlorides at 80 degrees C at 0.5 mol % loading, resulting in a >90 % yield of the respective biphenyl derivatives. The use of polar phase tags allows the efficient recovery of palladium-phosphine catalysts by simple phase separation of the catalyst-containing DMSO solution and the product-containing n-heptane phase. The high activity (TOF) of the catalyst remains almost constant over more than five reaction cycles, which involve the catalytic reaction, separation of the product phase from the catalyst phase, and addition of new reactants to initiate the next cycle. The Buchwald type biphenyl phosphines form the most active Pd catalysts, which are 1.3-2.8 times more active than catalysts derived from diadamantyl-benzylphosphine, but appear to be less robust in the recycling experiments. There is no apparent leaching of the catalyst into the heptane solution (<0.05 %), as evidenced by spectrophotometric measurements, and contamination of the product with Pd is avoided.
The most common method of sample preparation for Fourier transform infrared spectroscopic analysis of proteins in the solid state is compression after mixing with potassium bromide (KBr). Recently, questions have arisen as to whether proteins are conformationally altered by this process. In this study, the amide I Fourier transform infrared spectra of two model proteins, lysozyme and alpha-chymotrypsinogen, were measured before and after compression in KBr, and the effects of moisture exposure and the ratio of KBr to protein were examined. Contrary to earlier reports, compaction of the KBr/protein mixtures did not foster aggregation, and only minor apparent structural alterations were observed.