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81.
Mohammad M. Mojtahedi M. Saeed Abaee Mashal Javadpour 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2362-2365
Solvent-free protection of aromatic and aliphatic thiols with acetic anhydride was performed at room temperature under trace quantities of magnesium bromide ethyl etherate, affording rapid formation of various thiol esters in excellent yields. 相似文献
82.
Thressa C. Stadtman 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):199-216
Abstract Some enzymes known to contain selenium are enumerated. In four of them which catalyze coupled oxidation-reduction reactions the selenium occurs exclusively in the form of selenocysteine residues. Their structure and function are described in detail. Two other bacterial enzymes which contain selenium in the form of a labile, readily dissociable component are also described. Results on the isolation, identification and structure determination of selenium-containing amino acid transfer ribonucleic acids are presented. These seleno-t RNA's are shown to contain either 5-methyl-aminomethyl-2-selenouridine or other 2-selenouridine derivatives. The role of selenium in a glutamate iso-accepter species is discussed. 相似文献
83.
A. A. Fadda H. A. Etman A. A. Sarhan Sherihan A. El-Hadidy 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):526-536
2-Cyano-N-(tetrahydrocarbazole)acetamide (1) was utilized for the synthesis of several new arylazocarbazole derivatives (2a–e). Compound (1) reacted with phenyl isothiocyanate to yield the corresponding non-isolable intermediate (3), which gave, upon treatment with dilute hydrochloric acid, thiocarbamoyl derivative (4). Compound (3) reacted with chloroacetone, chloroacetic acid, chloroacetyl chloride, ethyl bromoacetate, and phenacyl bromide to afford thiazolone derivatives (6), (8), and (10), respectively. Compound (1) was heated in the presence of pyridine and/or hydrazine hydrate and/or isatine to give the corresponding tetrahydrocarbazole derivatives (13), (14), and (18), respectively. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
84.
A. Bialski R. J. St. Manley M. R. Wertheimer H. P. Schreiber 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):609-618
A Large-volume Microwave Plasma (LMP) generator has been used to irradiate mica and ground-wood fibers in inert and active gas environments. Irradiated fillers were subsequently incorporated in a polypropylene matrix at solids levels of 10 and 20%. Calorimetrically measured heats of immersion showed that substantial changes in surface properties of fillers were effected by irradiation in ethylene, ammonia, and similar active gases. These surface changes are reflected In ultimate tensile and elongation properties of composites which show marked improvement over controls based on unirradiated fillers. Although no appreciable response in melt viscosity has been observed, surface treatment of fillers does seem to increase significantly melt elasticity of filled composites. The implications of improved performance motivate a more detailed study of the use potential of LMP in the fomulation of polymer composites. 相似文献
85.
The synthesis and characterization of some substituted benzyl N-nitrosocarbamates with an N-2-(methylthio)ethyl or a bis(2-aminoethyl)sulfide functionality is reported, as a part of a long-term goal to design and prepare novel photolabile structures that could be used as substances for controlled release of alkylating and/or crosslinking agents. The synthesis was accomplished by reaction of benzyl chloroformates with the corresponding amines, resulting in the preparation of carbamates. The latter were subsequently nitrosated, utilizing two different N-nitrosation methods, to yield the target structures. 相似文献
86.
Jun‐Ju Xu Da‐Ke Zhao Hong‐Lian Ai Li‐Mei Zhang Shi‐Qing Xie Shu‐Hui Zi Sheng‐Chao Yang Yong Shen 《Helvetica chimica acta》2013,96(11):2155-2159
A further study of the alkaloid constituents of Aconitum forrestii led to the isolation of three new C19‐diterpenoid alkaloids, named 14‐acetoxy‐8‐O‐methylsachaconitine ( 1 ), 14‐acetoxyscaconine ( 2 ), and 8‐O‐ethylcammaconine ( 3 ). Their structures were determined by UV, IR, and MS, 1D‐ and 2D‐NMR analyses. 相似文献
87.
Reaction between 6‐(un)substituted‐2‐thiouracils and E‐ethyl 4‐bromocrotonate under basic conditions at room temperature is an easy, mild, high‐yielding, and regioselective method for the preparation of 7‐(un)substituted dihydrothiazolo[3,2‐a]pyrimidinone derivatives. 相似文献
88.
R. F. Addison 《International journal of environmental analytical chemistry》2013,93(4):287-292
Abstract Dow 2200 is a selective ore flotation agent, consisting mainly of Nethyl, 0-isopropyl thionocarbamate (IF'ETC). This paper describes a GLC method for the estimation of IPETC, and compares it with the conventional U.V. spectrophotometric procedure. An aliquot of a cyclohexane extract of IPETC (prepared for spectrophotometric analysis) is chromatographed on a column of SE-30 or OV-17/QF-1 at 125°C and the IPETC peak is estimated in a 3H electron capture detector (ECD). The ECD is superior in sensitivity and linearity of response to the flame photometric detector operated in the S-mode. The ECD-GLC procedure is comparable in sensitivity to the conventional U.V. absorbance method, and offers an independent and complementary procedure useful for confirmation of low levels of IPETC. 相似文献
89.
90.
Giovanna Bruni Ines Ghione Vittorio Berbenni Andrea Cardini Doretta Capsoni Alessandro Girella Chiara Milanese Amedeo Marini 《Molecules (Basel, Switzerland)》2021,26(11)
The present work is a concrete example of how physico-chemical studies, if performed in depth, are crucial to understand the behavior of pharmaceutical solids and constitute a solid basis for the control of the reproducibility of the industrial batches. In particular, a deep study of the thermal behavior of glipizide, a hypoglycemic drug, was carried out with the aim of clarifying whether the recognition of its polymorphic forms can really be done on the basis of the endothermic peak that the literature studies attribute to the melting of the compound. A number of analytical techniques were used: thermal techniques (DSC, TGA), X-ray powder diffraction (XRPD), FT-IR spectroscopy and scanning electron microscopy (SEM). Great attention was paid to the experimental design and to the interpretation of the combined results obtained by all these techniques. We proved that the attribution of the endothermic peak shown by glipizide to its melting was actually wrong. The DSC peak is no doubt triggered by a decomposition process that involves gas evolution (cyclohexanamine and carbon dioxide) and formation of 5-methyl-N-[2-(4-sulphamoylphenyl) ethyl] pyrazine-2-carboxamide, which remains as decomposition residue. Thermal treatments properly designed and the combined use of DSC with FT-IR and XRPD led to identifying a new polymorphic form of 5-methyl-N-[2-(4-sulphamoylphenyl) ethyl] pyrazine-2-carboxamide, which is obtained by crystallization from the melt. Hence, our results put into evidence that the check of the polymorphic form of glipizide cannot be based on the temperature values of the DSC peak, since such a peak is due to a decomposition process whose Tonset value is strongly affected by the particle size. Kinetic studies of the decomposition process show the high stability of solid glipizide at room temperature. 相似文献