نتایج جستجو برای: oxa michael reaction
تعداد نتایج: 437231 فیلتر نتایج به سال:
The synthesis of novel acetal thia-cage compounds has been accomplished by the direct substitution for the oxygen atom by the sulfur atom in the reaction of the acetal groups of oxa-cages with Lawesson reagent (LR). Reaction of the tetraoxa-cage compound 2 with LR in dichloromethane at 25 degrees C sequentially gave the monothia-, dithia-, trithia-, and tetrathia-cage compounds 3, 6, 7, and 9. ...
Background: The resistance of Pseudomonas aeruginosa strains to broad spectrum cephalosporins may be mediated by extended spectrum b-lactamases (ESBLs). These enzymes are encoded by different genes located either on chromosome or plasmids. In this study, we determined the antimicrobial resistance patterns of P. aeruginosa isolates and screened for ESBL production. Methods: After isolation from...
The reaction of PbCI, with 1,4,10,13-tetra-oxa-7, 16-diaza-cyclooctadecane (L= C H N O ) yielded colourless crystals of LPbCI . The complex crystallizes in monoclinic space group, C2/c, a = 7.90(2), b = 14.75(3) and C = 17.36(3) ?= ? 101.75(3)?, Z = 4 and R = 0.083 The coordination number around the lead atom is Eight . [Pb-N, 2.36(1), 2.70(4)], [Pb-0,2.41(3)-2.57(3)], [Pb-CI, 2.51(4), 2.5...
INTRODUCTION Recently Acinetobacter baumannii isolates have emerged as a problematic infectious agent that causes meningitis in neurosurgical patients. Colistin has been used successfully for the treatment of A. baumannii meningitis but colistin resistant isolates have been reported worldwide. CASE PRESENTATION Two isolates of A. baumannii were cultured during a five-day period from cerebrosp...
BACKGROUND For over two decades, a racemic mixture of oxamniquine (OXA) was administered to patients infected by Schistosoma mansoni, but whether one or both enantiomers exert antischistosomal activity was unknown. Recently, a ~30 kDa S. mansoni sulfotransferase (SmSULT) was identified as the target of OXA action. METHODOLOGY/PRINCIPAL FINDINGS Here, we separate the OXA enantiomers using chro...
Background and Objective: Acinetobacter baumannii is considered as an important agent in nosocomial infections. The problem facing the tratment of these bacteria is increasing resistance to antimicrobial agents such as carbapenems. The main mechanism of resistance to carbapenems in these bacteria is the presence of oxacillinases genes, which belong to class D betalactamases. The aim of this st...
INTRODUCTION bla(OXA-48) is a globally emerging carbapenemase-encoding gene. The progenitor of bla(OXA-48) appears to be a Shewanella species. The presence of the bla(OXA-48)-like gene was investigated for two Shewanella xiamenensis strains. METHODS Strain WCJ25 was recovered from post-surgical abdominal drainages, while S4 was the type strain of S. xiamenensis. Species identification for WCJ...
Given the significance of carbohydrates in life, medicine, and industry, the development of simple and efficient de novo methods to synthesize carbohydrates are highly desirable. Organocatalytic asymmetric assembly reactions are powerful tools to rapidly construct molecules with stereochemical complexity from simple precursors. Here, we present a simple and robust methodology for the asymmetric...
silica ferric hydrogensulfate is an efficient heterogeneous catalyst for the cyclization of 2- aminochalcones to the corresponding 2,3-dihydroquinolin- 4(1h)-ones. this intramolecular aza michael reaction was carried out in high yields using chalcones bearing of electron donating and electron withdrawing groups. the catalyst is reusable without significant decreases in its activity after four t...
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