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Various Substituents (various + substituent)
Selected AbstractsChemInform Abstract: Synthesis and Biological Activity of Permethrin Analogues Containing Various Substituents in Position 2 of the Cyclopropane Ring.CHEMINFORM, Issue 36 2009N. S. Mirzabekova Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Synthesis and Triethylamine-Catalyzed Cyclization Reaction of 4-Pentyne-1,3-dione System Having Various Substituents.CHEMINFORM, Issue 9 2009Hirofumi Kuroda Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Recent cancer drug development with xanthone structuresJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2009Younghwa Na Abstract Objectives Xanthones are simple three-membered ring compounds that are mainly found as secondary metabolites in higher plants and microorganisms. Xanthones have very diverse biological profiles, including antihypertensive, antioxidative, antithrombotic and anticancer activity, depending on their diverse structures, which are modified by substituents on the ring system. Although several reviews have already been published on xanthone compounds, few of them have focused on the anticancer activity of xanthone derivatives. In this review we briefly summarize natural and synthetic xanthone compounds which have potential as anticancer drugs. Key findings The interesting structural scaffold and pharmacological importance of xanthone derivatives have led many scientists to isolate or synthesize these compounds as novel drug candidates. In the past, extensive research has been conducted to obtain xanthone derivatives from natural resources as well as through synthetic chemistry. Xanthones interact with various pharmacological targets based on the different substituents on the core ring. The anticancer activities of xanthones are also dramatically altered by the ring substituents and their positions. Summary The biological activities of synthetic xanthone derivatives depend on the various substituents and their position. Study of the biological mechanism of action of xanthone analogues, however, has not been conducted extensively compared to the diversity of xanthone compounds. Elucidation of the exact biological target of xanthone compounds will provide better opportunities for these compounds to be developed as potent anticancer drugs. At the same time, modification of natural xanthone derivatives aimed at specific targets is capable of expanding the biological spectrum of xanthone compounds. [source] Heterocyclic polyimides containing siloxane groups in the main chainPOLYMER INTERNATIONAL, Issue 9 2009Mariana-Dana Damaceanu Abstract BACKGROUND: Among the polymers widely studied for applications in advanced techniques, aromatic polyimides have received considerable attention due to their outstanding thermal stability associated with good electrical and mechanical properties. However, these polymers are usually difficult to process, being insoluble and without a glass transition. To improve the processing characteristics of polyimides, modification of their structure is often achieved by the introduction of flexible linkages in the macromolecular chain or various substituents on the aromatic rings. RESULTS: A series of polyimides and intermediate polyamidic acids were synthesized from aromatic oxadiazole-diamines and a dianhydride containing a siloxane bridge (R2SiOSiR2). These polymers exhibit good solubility in certain organic solvents and can be cast into thin and very thin films from their solutions. They exhibit high thermal stability with decomposition being above 440 °C and relatively low glass transition temperatures in the range 160,190 °C. These polymers show strong photoluminescence in the blue spectral region. CONCLUSION: The introduction of oxadiazole rings together with siloxane groups into the chains of aromatic polyimides gives highly thermostable polymers with remarkable solubility and film-forming ability and that emit blue light, being attractive for applications in micro- and nanoelectronics and other related advanced fields. Copyright © 2009 Society of Chemical Industry [source] New features on the fragmentation patterns of homoisoflavonoids in Ophiopogon japonicus by high-performance liquid chromatography/diode-array detection/electrospray ionization with multi-stage tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2010Jin Qi Homoisoflavonoids, a special class of flavonoids, are mainly distributed in the Liliaceae family and have various biological activities. Previously, very little research has been reported on the gas-phase fragmentation patterns of homoisoflavonoids by electrospray ionization mass spectrometry. In this paper, we report the use of high-performance liquid chromatography with a diode-array detector (HPLC-DAD) and electrospray ionization multi-stage tandem mass spectrometry (ESI-MSn) to study the fragmentation behavior of 11 homoisoflavonoid standards and to analyze homoisoflavonoids in Ophiopogon japonicus. In total, 28 homoisoflavonoids (including seven novel constituents) were characterized. The deprotonated [MH], molecules of the homoisoflavonoids containing a saturated C2C3 bond afforded the A or B product ion (base peak) according to whether the B-ring was substituted with a hydroxyl group. For the homoisoflavonoids containing a C-2C-3 double bond, the product ions (A or C ion) were created from the precursor [MH], ion as the base peak when the B-ring was substituted with a hydroxyl group. The homoisoflavonoids carrying a formyl group in the A-ring readily eliminated one molecule of CO to form the product ion [M,+,HCO], (base peak) irrespective whether the C-2C-3 bond was saturated or not. This product ion afforded the [MHCOB-ringCH2,+,H], ion by cleavage of the C3C9 bond. This latter product ion always appeared in tandem mass (MS/MS) spectra of type I homoisoflavonoids. The common features of flavonoids observed during the gas-phase fragmentation mechanisms were the loss of the following groups: 15,Da (CH3), 18,Da (H2O), 28,Da (CO), 44,Da (CO2) and 46,Da (CH2O2). A retro-Diels-Alder (RDA)-like cleavage was also observed for the homoisoflavonoids. The different gas-phase fragmentation routes were characterized for the deprotonated molecules obtained from the various homoisoflavonoids and collision-induced dissociation (CID) fragmentation differences were noted for the different locations of the various substituents. In conclusion, we can say that this study allowed us to structurally elucidate and identify homoisoflavonoids distributed in related plants and their complex prescriptions. Copyright © 2010 John Wiley & Sons, Ltd. [source] Regio- and stereospecific synthesis of polysubstituted alkenes by carbozincation of acetylenic sulfonesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2009Meihua Xie Abstract Tri- or tetrasubstituted alkenes with various substituents can be constructed regio- and stereospecifically by treatment of acetylenic sulfones with organozinc reagents in tetrahydrofuran followed by hydrolysis or coupling with halohydrocarbon. Copyright © 2009 John Wiley & Sons, Ltd. [source] Synthesis, structure and reactivity of cationic base-stabilized gallyleneiron complexes,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 6-7 2003Keiji Ueno Abstract Addition of 2,2,-bipyridine (bpy) to an acetonitrile solution of dichlorogallyliron complex FpGaCl2 (1: Fp = (,-C5H5)Fe(CO)2) afforded almost quantitatively a salt consisting of a cationic base-stabilized gallylene complex [FpGaCl·bpy]+ ([3a]+) and an anionic complex [FpGaCl3], ([4],). Reaction of Fp,GaCl2 (Fp, = Fp (1), Fp* (2); Fp* = (,-C5Me5)Fe(CO)2) with NaBPh4 in the presence of a bidentate donor (Do2) gave [Fp,GaCl·Do2]BPh4 where Do2 was bpy or 1,10-phenanthroline (phen). These cationic complexes may be useful precursors for the synthesis of gallyleneiron complexes with various substituents on the gallium atom. Indeed, reaction of [Fp*GaCl·phen]BPh4 ([5b]BPh4) with NaSpTol or Me3SiSpTol afforded the gallyleneiron complex [Fp*GaSpTol·phen]BPh4 ([6]BPh4), the first example of a gallium,transition metal complex having a thiolate group on the gallium atom. The molecular structures of [5b]BPh4 and [6]BPh4 were determined by single crystal X-ray diffraction. Copyright © 2003 John Wiley & Sons, Ltd. [source] 9,10-Diarylanthracenes as Molecular Switches: Syntheses, Properties, Isomerisations and Their Reactions with Singlet OxygenCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2008Daniel Zehm Abstract A series of 9,10-diarylanthracenes with various substituents at the ortho positions have been synthesised by palladium-catalysed cross-coupling reactions. Such compounds exhibit interesting physical properties and can be applied as molecular switches. Despite the high steric demand of the substituents, products were formed in moderate-to-good yields. In some cases, microwave conditions further improved yields. Bis-coupling afforded two isomers (syn and anti) that do not interconvert at room temperature. These products were easily separated and their relative stereochemistries were unequivocally assigned by NMR spectroscopy and X-ray analysis. The syn and anti isomers exhibit different physical properties (e.g., melting points and solubilities) and interconversion by rotation around the aryl,aryl axis commences at <100,°C for fluoro-substituted diarylanthracenes and at >300,°C for alkyl- or alkoxy-substituted diarylanthracenes. The reactions with singlet oxygen were studied separately and revealed different reactivities and reaction pathways. The yields and reactivities depend on the size and electronic nature of the substituents. The anti isomers form the same 9,10-endoperoxides as the syn species, occasionally accompanied by unexpected 1,4-endoperoxides as byproducts. Thermolysis of the endoperoxides exclusively yielded the syn isomers. The interesting rotation around the aryl,aryl axis allows the application of 9,10-diarylanthracenes as molecular switches, which are triggered by light and air under mild conditions. Finally, the oxygenation and thermolysis sequence provides a simple, synthetic access to a single stereoisomer (syn) from an unselective coupling step. [source] Effective Manipulation of the Electronic Effects and Its Influence on the Emission of 5-Substituted Tris(8-quinolinolate) Aluminum(III) ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2006Victor A. Montes Abstract The unique electron-transport and emissive properties of tris(8-quinolinolate) aluminum(III) (Alq3) have resulted in extensive use of this material for small molecular organic light-emitting diode (OLED) fabrication. So far, efforts to prepare stable and easy-to-process red/green/blue (RGB)-emitting Alq3 derivatives have met with only a limited success. In this paper, we describe how the electronic nature of various substituents, projected via an arylethynyl or aryl spacer to the position of the highest HOMO density (C5), may be used for effective emission tuning to obtain blue-, green-, and red-emitting materials. The synthetic strategy consists of four different pathways for the attachment of electron-donating and electron-withdrawing aryl or arylethynyl substituents to the 5-position of the quinolinolate ring. Successful tuning of the emission color covering the whole visible spectrum (,=450,800 nm) was achieved. In addition, the photophysical properties of the luminophores were found to correlate with the Hammett constant of the respective substituents, providing a powerful strategy with which to predict the optical properties of new materials. We also demonstrate that the electronic nature of the substituent affects the emission properties of the resulting complex through effective modification of the HOMO levels of the quinolinolate ligand. [source] | ||||||||||