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81.
A concise approach for the transformation of various S-amino acids into the 5-alkyl-3-phenyl-2-thioxoimidazolidin-4-one heterocycles using phenylisothiocyanate is described. Phenylthiohydantoins of amino acid were synthesized at room temperature in Et3N/DMF-H2O with easy workup and excellent yields. 相似文献
82.
A carbon-monoxide-free aminocarbonylation of various N-substituted formamides with aryl iodides and aryl bromides using palladium acetate and Xantphos is described. The developed methodology is applicable for a wide range of formamides and aryl halides containing different functional groups furnishing good to excellent yield of the corresponding products. N-substituted formamides are used as an amide source wherein a Vilsmeier-type intermediate plays a major role, thus eliminating the need of toxic carbon monoxide gas. 相似文献
83.
Velvadapu V Paul T Wagh B Glassford I DeBrosse C Andrade RB 《The Journal of organic chemistry》2011,76(18):7516-7527
Novel sources of antibiotics are required to address the serious problem of antibiotic resistance. Telithromycin (2) is a third-generation macrolide antibiotic prepared from erythromycin (1) and used clinically since 2004. Herein we report the details of our efforts that ultimately led to the total synthesis of (-)-4,8,10-tridesmethyl telithromycin (3) wherein methyl groups have been replaced with hydrogens. The synthesis of desmethyl macrolides has emerged as a novel strategy for preparing bioactive antibiotics. 相似文献
84.
We have derived analytic expressions for the deflection as well as transmitted fraction of monochromatic neutrons forward
diffracted by a single crystal prism. In the vicinity of a Bragg reflection, the neutron deflection deviates sharply from
that for an amorphous prism, exhibiting three orders of magnitude greater sensitivity to the incidence angle. We have measured
the variation of neutron deflection and transmission across a Bragg reflection, for several single crystal prisms. The results
agree well with theory.
相似文献
85.
Observations on surface microtopography of flux grown CdS crystals are reported. Crystals resulting with cooling rate above 30 °C/hr are reported to be dendritic crystals, while those with cooling rate below 30 °C/hr are reported to be normal crystals like mineral greenockite as reported in standard books on mineralogy. Reasoning for dendritic growth is briefly discussed. Growth patterns and etch pits formation on them are interpreted. It is established that these crystals grow by two-dimensional nucleation mechanism and by spreading and piling of growth layers. 相似文献