Metabolites of A Novel Antibiotic Bitespiramycin in Rat Urine and Bile

A sensitive analytical method to identify active metabolites of bitespiramycin in rat urine and bile was developed by liquid chromatography-electrospray ionization tandem mass spectrometry(LC/ESI-MS^n).Bitespiramycin and its major active metabolites in rat urine and bile were isolated and identified as M1 serial(spiramycin Ⅰ，Ⅱ，Ⅲ),M2 serial(platenomycin A1,josamycin and leucomycin A1) and M3 serial(deisovalerylplatenomycin A1,deisovaleryljosamycin,deisovalerylleucomycin A1).     

Baker＇s Yeast Mediated Reduction of Optically Active Diketone

Baker‘s yeast mediated reduction of optically active diketone is described. The two keto groups are efficiently differentiated and the ee value of the recovered material is considerably raised. It affords highly optically active key intermediates efficiently for the synthesis of natural polyhydroxylated agarofuran products.     

The First and Facile Synthesis of (±) Syringaresinol

The first and facile synthesis of (±)syringaresinol was described.     

Synthesis and Structure of Mixed Phosphonium-iodonium Ylide

A mixed phosphonium-iodonium ylide, phenyliodoniumethoxycarbonylmethylenetriphenylphosphorane borofluoride, was synthesized. Its structure was established by means of X-ray diffraction analysis. Temperature dependence of ¹H, ¹³C, and ³¹P spectra of the ylide synthesized was investigated. A dynamic equilibrium between Z and E-isomers was observed.     

Two-Frequency Autowave Processes in the Complex Ginzburg–Landau Equation

We study the complex Ginzburg–Landau equation with zero Neumann boundary conditions on a finite interval and establish that this boundary problem (with suitably chosen parameters) has countably many stable two-dimensional self-similar tori. The case of periodic boundary conditions is also investigated.     

Transition flow of rarefied gases: Current models and methods of simulation

Transition (molecular-viscous) isothermal channel flow of rarefied gases is considered. Present-day engineering physical models of transition gas flow and methods of simulation are analyzed and verified in terms of the kinetic theory on the micro-and macrolevels.     

Electron-stimulated desorption of potassium and cesium atoms from an oxidized molybdenum surface

The yield and energy distributions of potassium and cesium atoms emitted in electron-stimulated desorption (ESD) from a molybdenum surface, oxidized to different extent and maintained at 300 K, have been measured by the time-of-flight technique with a surface ionization detector. The ESD threshold for potassium and cesium atoms lies around 25 eV, irrespective of molybdenum oxidation state. In the case of molybdenum coated by an oxygen monolayer, secondary thresholds at ∼40 and ∼70 eV have been observed, as well as atomic energy distribution tailing down to very low energies. The most probable kinetic energies of the atoms are a few tenths of one eV. The results are explained within a model involving Auger neutralization of the adsorbed alkali metal ions after the filling of the 2s O, 4s Mo, and 4p Mo core holes. The possibility of ESD of a neutral species as a result of oxide-cation core-level ionization has been demonstrated for the first time. Fiz. Tverd. Tela (St. Petersburg) 39, 758–761 (April 1997)