Preparation of clarithromycin. Selective 6-O-methylation of the novel erythromycin A 9-O-(2-pyrimidyl)oxime

A new method for the preparation of clarithromycin is described through the highly regioselective O-methylation at C(6)-OH of the novel derivative 9-pyrimidyloxime erythromycin A. The facile synthesis of 6,11-O-dimethyl- and 6,11,12-O-trimethyl erythromycin A is also reported. These compounds are useful as standards to assess clarithromycin purity in quality control processes.     

Computation in kinetics, III. A new method for kinetic model search based on simultaneous regression estimation of rate constants, stoichiometry and/or reaction order

Modified samples of natural mordenites have been found to catalyze the oxidative condensation of methane to yield ethane and ethylene. The selectivity towards C₂ hydrocarbons increases, whereas the acidity of zeolites falls.

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Investigation of Raman,FT-IR,EPR spectra and antimicrobial activity of 2-(5-H/Me/Cl-1<Emphasis Type="BoldItalic">H</Emphasis>-benzimidazol-2-yl)-phenol ligands and their Fe(NO<Subscript>3</Subscript>)<Subscript>3</Subscript> complexes

2-(5-H/Me/Cl-1H-benzimidazol-2-yl)-phenol ligands form 1:1 electrolytes, 5-coordinate monometallic complexes with iron(III) nitrate. The geometry of the [Fe(L)(OH)(H₂O)₂](NO₃) complexes was derived from theoretical calculation in DGauss/DFT level (DZVP basis set) on CACHE. In all of the complexes the ligands are bidentate, via one imine nitrogen atom and phenolate oxygen atom. The coordination is completed with a hydroxide ion, and two water molecules, adopting a distorted square pyramidal geometry. The structures of the compounds were confirmed on the basis of elemental analysis, molar conductivity, magnetic moment, FT-Raman, FT-IR (mid-IR, far-IR), EPR and u.v.–vis. The antimicrobial activities of the free ligands, their hydrochloride salts, and the complexes were evaluated using the disk diffusion method in dimethyl sulfoxide (DMSO) as well as the minimal inhibitory concentration (MIC) dilution method, against nine bacteria and the results are compared with several known antibiotic agents. Antifungal activities were reported for Candida albicans, Kluyveromyces fragilis, Rhodotorula rubra, Debaryomyces hansenii, Hanseniaspora guilliermondii, and the results were referenced against nystatin, ketaconazole, and clotrimazole antifungal agents. In most cases, the compounds tested showed broad-spectrum (Gram⁺ & Gram⁻ bacteria) activities that were either more active or as potent as the references.     

Synthesis of 1,2-Diphenylpyrazolidin-4-ol and its Derivatives

Summary. A synthesis of 1,2-diphenylpyrazolidin-4-ol via direct heterocyclization of 1,2-diphenylhydrazine with 1-chloro-2,3-epoxypropane, its O-epoxypropyl-, O-ethyl-, and O-benzylderivatives are described. Novel hydrazone derivatives with pyrazolidine units were also synthesized. The compounds were characterized by spectroscopic methods as well as elemental analyses.     

脂肪族酰胺二元醇的合成与表征

以ＤＬ－乳酸、ε己内酯及乙二胺和己二胺为原料合成了四种结构的脂肪族酰胺二元醇，并用ＩＲ，＾１ＨＮＭＲ，ＤＳＣ对酰胺二元醇的结构进行了表征。     

Equilibrium and Kinetics of NO and CO Chemisorptions on Nonstoichiometric Nickel-Copper Manganites

The equilibrium and kinetics of adsorption of NO and CO on nonstoichiometric nickel-copper manganites have been investigated through volumetric measurements. The adsorption isotherms were satisfactorily fitted to the Freundlich equation. The equilibrium coverages at 298 K were found to depend closely on the chemical composition of the oxide; thus, a decrease in the coverage beyond a maximum copper extent was observed. The adsorption isotherms of NO at various temperatures in the range from 298 to 473 K showed that the equilibrium coverage decreases with increasing temperature. This behavior enabled us to follow the logarithmic decrease of the heat of adsorption of NO on such surfaces. The adsorptions of NO and CO on surfaces preadsorbed with CO and NO, respectively, were also studied. These experiments showed the ability of NO to displace CO preadsorbed molecules whereas the contrary did not hold, suggesting the existence of common adsorption sites as well as some specific CO adsorption sites. Finally, some kinetic data are reported showing that the experimental adsorption results fit the Elovich equation (with t(0) approximately 0), although two distinct rate processes could be identified. Copyright 2000 Academic Press.     

Synthesis of highly textured superconducting NdBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7-<Emphasis Type="Italic">y</Emphasis></Subscript> thin films by two aqueous sol-gel dip coating techniques

Today, the deposition of coated conductors on a variety of substrates is often performed using a vacuum or low pressure technique. However, obtaining uninterrupted deposition at high speed, increasing flexibility in composition and attaining independence of geometric constraints of the substrates are areas in which vacuum techniques will need sustained development in order to answer industrial demands. The development of the next generation of deposition methods, based on deposition under atmospheric environment and from aqueous precursor solutions is a real challenge. This work describes the deposition of thin NdBa₂Cu₃O_7-y layers on SrTiO₃ single crystals based on a new sol-gel dip coating process using aqueous precursor solutions. Two inorganic aqueous sol-gel routes were investigated, a metal nitrate–citric acid based and a metal acetate–triethanol amine based solution. Using detailed thermal analysis, it is shown that adjusting the different parameters during thermal treatment can be used to control the morphology of the films. Also special attention is given to the microstructure of the thin film because of its relevance to the superconducting transport properties of the coated conductor system.     

Determination of 19-norandrosterone in CCQM-P68. NIST results using an isotope dilution liquid chromatography/tandem mass spectrometry method

The US National Institute of Standards and Technology (NIST) participated in an international interlaboratory study under the auspices of the Consultative Committee for Amount of Substance (CCQM) for the determination of 19-norandrosterone (19-NA) in urine, the principal metabolite of nandrolone and certain other synthetic testosterone substitutes banned for use by the World Antidoping Agency (WADA). Prior to this study, NIST developed a candidate reference measurement procedure based upon isotope dilution liquid chromatography/tandem mass spectrometry. This method was applied to a urine sample distributed to the participants in the study by the Australian National Measurement Institute, Pymble, Australia (NMIA). The NIST results were in very good agreement with those from the other participants, all of whom used methods based upon gas chromatography/mass spectrometry. All known significant sources of uncertainty were evaluated, resulting in a relative expanded uncertainty of less than 5% (coverage factor k = 2).     

Sphericities of Double Cosets,Double Coset Representations,and Fujita’s Proligand Method for Combinatorial Enumeration of Stereoisomers

The concepts of double coset representations and sphericities of double cosets are proposed to characterize stereoisomerism, where double cosets are classified into three types, i.e., homospheric double cosets, enantiospheric double cosets, or hemispheric double cosets. They determine modes of substitutions (i.e., chirality fittingness), where homospheric double cosets permit achiral ligands only; enantiospheric ones permit achiral ligands or enantiomeric pairs; and hemispheric ones permit achiral and chiral ligands. The sphericities of double cosets are linked to the sphericities of cycles which are ascribed to right coset representations. Thus, each cycle is assigned to the corresponding sphericity index (a _d , c _d , or b _d ) so as to construct a cycle indices with chirality fittingness (CI-CFs). The resulting CI-CFs are proved to be identical with CI-CFs introduced in Fujita’s proligand method (S. Fujita, Theor. Chem. Acc. 113 (2005) 73–79 and 80–86). The versatility of the CI-CFs in combinatorial enumeration of stereoisomers is demonstrated by using methane derivatives as examples, where the numbers of achiral plus chiral stereoisomers, those of achiral stereoisomers, and those of chiral stereoisomers are calculated separately by means of respective generating functions.     

An Abietane Diterpene and a Sterol from Fungus Phettinus igniarius

A new abietane diterpene 12-hydroxy-7-oxo-5, 8, 11, 13-tetraene-18, 6-abietanolide, together with a new natural sterol stigmasta-7, 22-diene-3β, 5α, 6α-triol have been isolated from the fruiting body of the fungus Phellinus igniarius. Their structures were elucidated by spectroscopic methods including 2D NMR techniques.