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Jetze J. Tepe - One of the best experts on this subject based on the ideXlab platform.
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One-pot Friedel-Crafts/Robinson-Gabriel synthesis of oxazoles using Oxazolone templates.
The Journal of organic chemistry, 2005Co-Authors: Manasi Keni, Jetze J. TepeAbstract:We report herein a one-pot synthesis of 2,4,5-trisubstituted oxazoles via a Friedel−Crafts/Robinson−Gabriel synthesis using a general Oxazolone template. Treatment of the Oxazolone template with a range of aromatic nucleophiles provided the highly substituted oxazoles in good yields.
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one pot friedel crafts robinson gabriel synthesis of oxazoles using Oxazolone templates
Journal of Organic Chemistry, 2005Co-Authors: Manasi Keni, Jetze J. TepeAbstract:We report herein a one-pot synthesis of 2,4,5-trisubstituted oxazoles via a Friedel−Crafts/Robinson−Gabriel synthesis using a general Oxazolone template. Treatment of the Oxazolone template with a range of aromatic nucleophiles provided the highly substituted oxazoles in good yields.
Manasi Keni - One of the best experts on this subject based on the ideXlab platform.
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One-pot Friedel-Crafts/Robinson-Gabriel synthesis of oxazoles using Oxazolone templates.
The Journal of organic chemistry, 2005Co-Authors: Manasi Keni, Jetze J. TepeAbstract:We report herein a one-pot synthesis of 2,4,5-trisubstituted oxazoles via a Friedel−Crafts/Robinson−Gabriel synthesis using a general Oxazolone template. Treatment of the Oxazolone template with a range of aromatic nucleophiles provided the highly substituted oxazoles in good yields.
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one pot friedel crafts robinson gabriel synthesis of oxazoles using Oxazolone templates
Journal of Organic Chemistry, 2005Co-Authors: Manasi Keni, Jetze J. TepeAbstract:We report herein a one-pot synthesis of 2,4,5-trisubstituted oxazoles via a Friedel−Crafts/Robinson−Gabriel synthesis using a general Oxazolone template. Treatment of the Oxazolone template with a range of aromatic nucleophiles provided the highly substituted oxazoles in good yields.
Chrys Wesdemiotis - One of the best experts on this subject based on the ideXlab platform.
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dissociation of the peptide bond in protonated peptides
Journal of Mass Spectrometry, 2000Co-Authors: Michael J Polce, Chrys WesdemiotisAbstract:The dissociation of the amide (peptide) bond in protonated peptides, [M + H]+, is discussed in terms of the structures and energetics of the resulting N-terminal bn and C-terminal yn sequence ions. The combined data provide strong evidence that dissociation proceeds with no reverse barriers through interconverting proton-bound complexes between the segments emerging upon cleavage of the protonated peptide bond. These complexes contain the C-terminal part as a smaller linear peptide (amino acid if one residue) and the N-terminal part either as an Oxazolone or a cyclic peptide (cyclic amide if one residue). Owing to the higher thermodynamic stability but substantially lower gas-phase basicity of cyclic peptides vs isomeric Oxazolones, the N-terminus is cleaved as a protonated Oxazolone when ionic (bn series) but as a cyclic peptide when neutral (accompanying the C-terminal yn series). It is demonstrated that free energy correlations can be used to derive thermochemical data about sequence ions. In this context, the dependence of the logarithm of the abundance ratio log[y1/b2], from protonated GGX (G, glycine; X, varying amino acid) on the gas-phase basicity of X is used to obtain a first experimental estimate of the gas-phase basicity of the simplest b-type Oxazolone, viz. 2-aminomethyl-5-Oxazolone (b2 ion with two glycyl residues). Copyright © 2000 John Wiley & Sons, Ltd.
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Proton affinities of the N- and C-terminal segments arising upon the dissociation of the amide bond in protonated peptides
Journal of the American Society for Mass Spectrometry, 1999Co-Authors: Michael J Nold, Blas A. Cerda, Chrys WesdemiotisAbstract:Dissociation of the amide bonds in a protonated peptide leads to N-terminal sequence fragments with cyclic structures and C-terminal sequence fragments with linear structures. The ionic fragments containing the N-terminus (b_ n ) have been shown to be protonated Oxazolones, whereas those containing the C-terminus (y_ n ) are protonated linear peptides. The coproduced neutral fragments are cyclic peptides from the N-terminus and linear peptides from the C-terminus. A likely determinant of these structural choices is the proton affinity (PA) of the described peptide segments. This study determines the PA values of such segments (Pep), i.e., cyclic and linear dipeptides and a relevant Oxazolone, based on the dissociations of proton-bound dimers [Pep + B_ i ]H^+ in which B_ i is a reference base of known PA value (Cooks kinetic method). The dissociations are assessed at different internal energies to thereby obtain both proton affinities as well as entropies of protonation. For species with comparable amino acid composition, the proton affinity (and gas phase basicity) follows the order cyclic peptide ≪ Oxazolone ≈ linear peptide. This ranking is consistent with dissociation of the protonated peptide via interconverting proton-bound complexes involving N-terminal Oxazolone (O) or cyclopeptide (C) segments and C-terminal linear peptide segments (L), viz. O ⋯ H^+ ⋯ L ⇄ C ⋯ H^+ ⋯ L. N-terminal sequence ions (b_ n ) are formed with Oxazolone structures which can efficiently compete for the proton with the linear segments. On the other hand, N-terminal neutral fragments detach as cyclic peptides, with H^+ now being retained by the more basic linear segment from the C-terminus to yield y_ n .
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amide bond dissociation in protonated peptides structures of the n terminal ionic and neutral fragments
International Journal of Mass Spectrometry and Ion Processes, 1997Co-Authors: Michael J Nold, Chrys Wesdemiotis, Talat Yalcin, Alex G HarrisonAbstract:Three-stage tandem mass spectrometry (MS3) and neutral fragment reionization (NfR) are utilized to investigate the structures of the N-terminal ionic (bi) and neutral backbone fragments, respectively, produced from break-up of the amide bond in protonated peptides that have been collisionally activated. The b-type ion from [M+H]+ of C6H5CO-GF, which is produced by loss of the C-terminal phenylalanine, has the structure of protonated 2-phenyl-5-Oxazolone. Conversely, the neutral fragment accompanying the y-type ion (protonated phenylalanine) is 2-phenyl-5-Oxazolone. The b2 ions arising from [M+H]+ of underivatized tripeptides are also found to be protonated Oxazolones. On the other hand, the neutral fragments released from the N-terminus of the tripeptides upon formation of y1 are shown to be diketopiperazines and not Oxazolones. The combined MS3 and NfR data help propose dissociation mechanisms that account for the observed structures of ionic and neutral backbone fragments.
José M. G. Martinho - One of the best experts on this subject based on the ideXlab platform.
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Unsaturated Oxazolones as nonlinear fluorophores
Dyes and Pigments, 2013Co-Authors: Catarina A. B. Rodrigues, Inês F. A. Mariz, Ermelinda M. S. Maçôas, Carlos A. M. Afonso, José M. G. MartinhoAbstract:Abstract Unwanted bleaching of two-photon absorption microscopy probes can be reduced by designing more efficient nonlinear fluorophores. Here the linear and nonlinear photophysical properties of unsaturated Oxazolones are studied. A set of push–pull Oxazolone derivatives have been designed by substituting the 2-phenyl-4-benzylidene-1,3-oxazol-5-one unit in two different positions with a combination of electron donor (dimethylaniline) and/or acceptor (nitro, nitrile and benzimidazole) groups. By engineering this green fluorescent protein analogue core we have prepared molecules with high two-photon absorption cross-sections 200–500 GM and fluorescence quantum yields up to 0.75. The factors determining the overall nonlinear emission efficiency of the new unsaturated Oxazolones are discussed in terms of the nature of the substituents.
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Two-photon absorption properties of push–pull Oxazolones derivatives
Dyes and Pigments, 2012Co-Authors: Catarina A. B. Rodrigues, Inês F. A. Mariz, Ermelinda M. S. Maçôas, Carlos A. M. Afonso, José M. G. MartinhoAbstract:Abstract New fluorescent Oxazolone derivatives with high two-photon absorption cross-section were synthesized. Electron donor (phenyl, dimethylaniline and furanyl) and acceptor (nitrobenzene and ethenyl-phenyl-benzimidazol) groups have been appended to the methylene end of 4-(methylidene)-2-phenyl-1,3-oxazol-5(4H)-one in order to produce an highly conjugated π-system with push–pull geometry. The linear and nonlinear optical properties of the Oxazolones have been determined. The compounds with a high charge transfer from the substituent group to the Oxazolone ring have relatively high two-photon absorption cross-sections (80–100 GM). The best performing nonlinear fluorophore being the benzimidazol derivative with a two-photon absorption cross-section of 80 GM and a relatively high emission quantum yield, ϕ = 0.31.
Haruhiko Manabe - One of the best experts on this subject based on the ideXlab platform.
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Gabapentin and pregabalin inhibit the itch-associated response induced by the repeated application of Oxazolone in mice.
Journal of pharmacological sciences, 2010Co-Authors: Yukihito Tsukumo, Yuichi Matsumoto, Hiroko Miura, Hiroshi Yano, Haruhiko ManabeAbstract:Abstract We investigated the effects of gabapentin and pregabalin on the itch-associated response in a mouse model of chronic dermatitis induced by the repeated application of 4-ethoxymethylene-2-phenyl-2-oxazolin-5-one (Oxazolone). Challenging the mice with Oxazolone-induced chronic dermatitis with the Oxazolone evoked severe and transient scratching behavior until 1 h after the application of Oxazolone. Thereafter, a more mild and continuous scratching behavior was also observed for at least 8 h. Both severe and continuous scratching behaviors were suppressed by systemic injection of gabapentin and pregabalin. This effect of these compounds was correlated with its affinity for the α2δ subunit of voltage-gated Ca2+ channels. Intrathecal injection, but not peripheral treatment, with gabapentin inhibited the scratching behavior in this model. Gabapentin failed to suppress the scratching behavior induced by the intradermal injection of compound 48/80 in normal mice. The expression of the α2δ-1 subunit in dorsal root ganglion (DRG) from mice following repeated application of Oxazolone was significantly higher than that from normal mice. These results suggest that gabapentin and pregabalin show an anti-pruritic activity through α2δ-subunit binding, and the up-regulation of the α2δ-1 subunit in DRG may therefore play an important role in its anti-pruritic activity.
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Pharmacological Characterization of Itch-Associated Response Induced by Repeated Application of Oxazolone in Mice
Journal of pharmacological sciences, 2010Co-Authors: Yukihito Tsukumo, Daisuke Harada, Haruhiko ManabeAbstract:Abstract We investigated pharmacological characteristics of the itch-associated response to chronic dermatitis induced by 4-ethoxymethylene-2-phenyl-2-oxazolin-5-one (Oxazolone) repeated application in mice. Application of an Oxazolone challenge to mice with Oxazolone-induced chronic dermatitis evoked severe and transient scratching behavior for up to 1h. Thereafter, mild and continuous scratching behavior was observed for at least 8 h. Both severe and continuous scratching behaviors were suppressed by the opioid-receptor antagonist naltrexone, but not by the H1 histamine–receptor antagonist fexofenadine, 5-hydroxytryptamine-2 (5-HT2)–receptor antagonist methysergide, NK1-receptor antagonist LY303870, cyclooxygenase inhibitor indomethacin, or the platelet-activating factor–receptor antagonist YM264. The severe scratching behavior was suppressed by the 5-lipoxygenase inhibitor zileuton and leukotriene B4–receptor antagonist ONO-4057, but not by the cysteinyl leukotriene–receptor antagonist montelukast. The continuous scratching behavior was suppressed by pretreatment with the non-selective muscarinic acetylcholine–receptor antagonist atropine and M3 muscarinic acetylcholine–receptor antagonist darifenacin. These results suggest that leukotriene B4 receptor and M3 muscarinic acetylcholine receptor are involved in the itch-associated response induced by repeated application of Oxazolone in mice.
