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Methoxy Substituent (methoxy + substituent)
Selected AbstractsOne-Pot Synthesis of Core-Modified Rubyrin, Octaphyrin, and Dodecaphyrin: Characterization and Nonlinear Optical PropertiesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 27 2007Rajeev Kumar Abstract Modified 26, rubyrin, 36, octaphyrin, and 54, dodecaphyrin systems have been synthesized in moderately good yields through acid-catalyzed condensations of terthiophene diols and tripyrranes. The product distributions are decided both by the acid catalyst concentration and by the nature of the meso substituents. For example, a new isomer of [26]hexaphyrin(1.1.1.1.0.0) (rubyrin) was obtained with 0.3 equiv. of p -toluenesulfonic acid, when the meso substituent was mesityl in at least one of the precursors. A change of the mesityl substituent for a p -methoxy substituent in terthiophene diol resulted in the formation of a [3,+,3,+,3,+,3] condensation product , [54]dodecaphyrin(1.1.1.1.0.0.1.1.1.1.0.0) , in addition to the expected rubyrin. Furthermore, an increase in the acid concentration to 0.6 equiv. resulted in the formation of a new [36]octaphyrin(1.1.1.1.1.1.0.0), in addition to the rubyrin and dodecaphyrin. A single-crystal X-ray analysis of octaphyrin represents the first example of a planar conformation of an octaphyrin with six meso links. In rubyrin 19, one thiophene ring, opposite to the terthiophene subunit, is inverted, while in octaphyrin 30 one pyrrole ring and two thiophene rings are inverted. The various conformational possibilities tested for the unsubstituted dodecaphyrin 28, at semiempirical level, suggest that the most stable conformation is a figure-eight. The final geometry optimization of figure-eight dodecaphyrin was done at the B3LYP/6-31G* level of DFT. Octaphyrins and dodecaphyrins bind trifluoroacetate anion effectively in their diprotonated forms, the binding constants (K) being 638 M,1 for dodecaphyrin 28, and 415 M,1 for octaphyrin 30. Electrochemical data reveal HOMO destabilization with increasing , electron conjugation, consistently with the large red shifts of the absorption bands. Preliminary studies on the use of these expanded porphyrins as third-order NLO materials were followed by measurements of their two-photon absorption (TPA) cross-sections [,(2)]. The ,(2) values increase upon going from the 26, rubyrins to the 54, dodecaphyrins, confirming our earlier observation that increases in ,-conjugated electrons increase the TPA values.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Alternative Mechanistic Paths in the Hetero-Diels,Alder Reaction of ,-Oxothiones: A Theoretical StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2007Laura Legnani Abstract DFT calculations at the B3LYP/6-311+G(d,p) level for the C, H, and O atoms and at the 6-311+G(2df,p) level for the S atom were used to study the hetero-Diels,Alder reactions between several ,-oxothiones and ethylene or methyl vinyl ether (MVE). All the transition states and the intermediates along the reaction pathways, as well as the reaction products, were located. The reactions with ethylene are all concerted though asynchronous whereas in the reactions with MVE the electron-releasing character of the methoxy substituent lowers the energy barriers and enhances the asynchronicity and the charge transfer process to such an extent that the reaction may become unconcerted and exhibit a two-step mechanism with a zwitterionic intermediate derived from nucleophilic attack of electron-rich MVE to the sulfur atom of the strongly electrophilically activated ,-oxothiones. The reactions are also favored by the conjugation of the newly formed C=C bond. Moreover, the geometric features of the diene exert a nonnegligible role, as dienes that are planar or almost planar in their ground state show a lower energy barrier. Thus, both geometric and electronic features of the dienes as well as of the dienophiles play a significant role in the easiness of the reactions and in their mechanism. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Design and Synthesis of 2-Phenoxynicotinic Acid Hydrazides as Anti-inflammatory and Analgesic AgentsARCHIV DER PHARMAZIE, Issue 9 2010Alireza Moradi Abstract A series of 2-phenoxynicotinic acid hydrazides were synthesized and evaluated for their analgesic and anti-inflammatory activities. Several compounds having an unsubstituted phenyl/4-pyridyl or C-4 methoxy substituent on the terminal phenyl ring showed moderate to high analgesic or anti-inflammatory activity in comparison to mefenamic acid as the reference drug. The compounds with highest anti-inflammatory activity were subjected to in vitro COX-1/COX-2 inhibition assays and showed moderate to good COX-1 and weak COX-2 inhibition activities. [source] Small molecule , -amyloid inhibitors that stabilize protofibrillar structures in vitro improve cognition and pathology in a mouse model of Alzheimer's diseaseEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2010Cheryl A. Hawkes Abstract ,-Amyloid (A,) peptides are thought to play a major role in the pathogenesis of Alzheimer's disease. Compounds that disrupt the kinetic pathways of A, aggregation may be useful in elucidating the role of oligomeric, protofibrillar and fibrillar A, in the etiology of the disease. We have previously reported that scyllo -inositol inhibits A,42 fibril formation but the mechanism(s) by which this occurs has not been investigated in detail. Using a series of scyllo -inositol derivatives in which one or two hydroxyl groups were replaced with hydrogen, chlorine or methoxy substituents, we examined the role of hydrogen bonding and hydrophobicity in the structure,function relationship of scyllo -inositol,A, binding. We report here that all scyllo -inositol derivatives demonstrated reduced effectiveness in preventing A,42 fibrillization compared with scyllo -inositol, suggesting that scyllo -inositol interacts with A,42 via key hydrogen bonds that are formed by all hydroxyl groups. Increasing the hydrophobicity of scyllo -inositol by the addition of two methoxy groups (1,4-di- O -methyl- scyllo -inositol) produced a derivative that stabilized A,42 protofibrils in vitro. Prophylactic administration of 1,4-di- O -methyl- scyllo -inositol to TgCRND8 mice attenuated spatial memory impairments and significantly decreased cerebral amyloid pathology. These results suggest that A, aggregation can be targeted at multiple points along the kinetic pathway for the improvement of Alzheimer's disease-like pathology. [source] Synthesis of Enantiopure Tricarbonyl(indan-1,2-dione)chromiumEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2005Dirk Leinweber Abstract A multistep synthesis of the planar chiral tricarbonyl(,6 -indan-1,2-dione)chromium, based on acetal protection of the keto groups, is presented. Since common deacetalization procedures failed, an oxidative deprotection with triphenylcarbenium tetrafluoroborate was used. Tricarbonyl(,6 -indan-1,2-dione)chromium is regarded as a potential precursor for dianionic oxy-Cope rearrangements upon alkenyllithium diaddition. As an unexpected side product in the synthesis, an indan-1,2-dione complex with a triphenylmethyl substituent at C-3 was obtained. Attempts directed towards the formation of enantiomerically pure material include the first reported investigation into an enantioselective ketone reduction with two methoxy substituents present in the , position. Although enantiomeric excesses of up to 84.5,% were achieved, the chemical yields decreased with increasing ee. A classical resolution was therefore undertaken, giving access to the enantiomerically pure title compound (99.4,% ee). The absolute configuration was verified by an X-ray structure analysis of an intermediate. First experiments concerning the alkenyllithium addition showed that a single addition is possible while a second one does not occur, presumably due to enolate formation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] The deuteriation of constituents in olive oil and red wine with Nafion, a polymer supported acid catalystJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 14 2001Kellie L. Tuck Abstract A procedure for the deuteriation of a large range of aromatic compounds with phenolic and methoxy substituents has been developed using Nafion, a polymer supported acid catalyst. A range of compounds present in red wine and olive oil were deuteriated using these conditions. This procedure provides a facile route for the labelling of homovanillic alcohol, homovanillic acid, syringic acid, syringaldehyde and vanillin. This method is also applicable for the tritiation of these compounds. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||