6971-18-2Relevant academic research and scientific papers
Ruthenium(II)-Catalyzed Synthesis of Spirobenzofuranones by a Decarbonylative Annulation Reaction
Kaishap, Partha P.,Duarah, Gauri,Sarma, Bipul,Chetia, Dipak,Gogoi, Sanjib
, p. 456 - 460 (2018/02/21)
The first decarbonylative insertion of an alkyne through C?H/C?C activation of six-membered compounds is reported. The Ru-catalyzed reaction of 3-hydroxy-2-phenyl-chromones with alkynes works most efficiently in the presence of the ligand PPh3 to provide spiro-indenebenzofuranones. Unlike previously reported metal-catalyzed decarbonylative annulation reactions, in the present decarbonylative annulation reaction, the annulation occurs before extrusion of carbon monoxide.
Antimicrobial effects of novel siderophores linked to β-lactam antibiotics
Kline,Fromhold,McKennon,Cai,Treiberg,Ihle,Sherman,Schwan,Hickey,Warrener,Witte,Brody,Goltry,Barker,Anderson,Tanaka,Shawar,Nguyen,Langhorne,Bigelow,Embuscado,Naeemi
, p. 73 - 93 (2007/10/03)
As a strategy to increase the penetration of antibiotic drugs through the outer membrane of Gram-negative pathogens, facilitated transport through siderophore receptors has been frequently exploited. Hydroxamic acids, catechols, or very close isosteres of catechols, which are mimics of naturally occurring siderophores, have been used successfully as covalently linked escorting moieties, but a much wider diversity of iron binding motifs exists. This observation, coupled to the relative lack of specificity of siderophore receptors, prompted us to initiate a program to identify novel, noncatechol siderophoric structures. We screened over 300 compounds for their ability to (1) support growth in low iron medium of a Pseudomonas aeruginosa siderophore biosynthesis deletion mutant, or (2) compete with a bactericidal siderophore-antibiotic conjugate for siderophore receptor access. From these assays we identified a set of small molecules that fulfilled one or both of these criteria. We then synthesized these compounds with functional groups suitable for attachment to both monobactam and cephalosporin core structures. Siderophore-β-lactam conjugates then were tested against a panel of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus strains. Although several of the resultant chimeric compounds had antimicrobial activity approaching that of ceftazidime, and most compounds demonstrated very potent activity against their cellular targets, only a single compound was obtained that had enhanced, siderophore-mediated antibacterial activity. Results with tonB mutants frequently showed increased rather than decreased susceptibilities, suggesting that multiple factors influenced the intracellular concentration of the drugs. (C) 2000 Elsevier Science Ltd.
Lithiation in Flavones, Chromones, Coumarins, and Benzofuran Derivatives
Costa, Ana M. B. S. R. C. S.,Dean, Francis M.,Jones, Michael A.,Varma, Rajender S.
, p. 799 - 808 (2007/10/02)
Flavones are lithiated at position 3 by lithium di-isopropylamide in tetrahydrofuran at -78 deg C and the products are stable at that temperature.Appropriate reagents replace the lithium by carboxy, ethoxycarbonyl, mercapto, methylthio, trimethylsilyl, hydroxy, and other groups, sometimes giving products not previously available.Benzofurans are preferentially lithiated at position 2 if this is free, and may not be attacked if it is blocked, but if there is an activating group (i.e., one able to co-ordinate with the lithium cation) at position 2, then lithiation occurs at position 3.In the benzofuran series ring-opening is easier and lithiation often leads directly to acetylenic phenols.Chromones can be lithiated at positions 2 and 3 depending upon the substitution pattern and whether the substituents are activating.Aurones are not easily deprotonated, and only the acetylenic phenol arising from ring opening was found in the one successful case.Coumarins tend to behave simply as esters and give amides with the lithiating reagent, but 4-methoxycoumarin is readily lithiated at position 3.It is suggested that 3-deprotonation in ethers occurs easily only when there is an ether link antiperiplanar to the proton removed, and that the lithiated species are really unstable intermediates in trans-eliminations leading to alkyne derivatives.
