- 2,6-Dihydroxybenzaldehyde Analogues of the Iron Chelator Salicylaldehyde Isonicotinoyl Hydrazone: Increased Hydrolytic Stability and Cytoprotective Activity against Oxidative Stress
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Salicylaldehyde isonicotinoyl hydrazone (SIH) is a small molecule and lipophilic chelating agent that firmly binds ferric ions from the cellular labile iron pool and is able to protect various tissues against oxidative damage. Previously, SIH possessed the best ratio of cytoprotective efficiency to toxicity among various iron chelators, including the desferrioxamine, deferiprone, and deferasirox used in clinical practice. Here, we prepared a series of 2,6-dihydroxybenzaldehyde aroylhydrazones as SIH analogues with an additional hydroxyl group that can be involved in the chelation of metal ions. Compound JK-31 (2,6-dihydroxybenzaldehyde 4-chlorobenzohydrazone) showed the best cytoprotective efficiency among the studied compounds including SIH. This compound significantly protected H9c2 cardiomyoblast cells against oxidative stress induced by various pro-oxidants, such as hydrogen peroxide, tert-butyl hydroperoxide, paraquat, epinephrine, N-acetyl-p-benzoquinone imine (a toxic metabolite of paracetamol), and 6-hydroxydopamine. The exceptional cytoprotective activity of JK-31 was confirmed using epifluorescence microscopy, where JK-31-treated H9c2 cells maintained a higher mitochondrial inner membrane potential in the presence of a lethal dose of hydrogen peroxide than was observed with cells treated with SIH. Hence, this study demonstrates the deleterious role of free iron ions in oxidative injury and the potential of 2,6-dihydroxybenzaldehyde aroylhydrazones in the prevention of various types of cardiac injuries, highlighting the need for further investigations into these compounds.
- Jansová, Hana,Kube?, Jan,Reimerová, Petra,?těrbová-Kova?íková, Petra,Roh, Jaroslav,?imunek, Tomá?
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Read Online
- Efficient and Mild Regeneration of Carbonyl Compounds from Oximes and Hydrazones by Manganese(III) Porphyrin-Periodate
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The periodate-manganese tetraphenylporphyrin, Mn(tpp)/1O4-, catalytic system is efficient in regenerating the parent carbonyl compounds from oximes and phenylhydrazones at room temperature.
- Tangestaninejad, Shahram,Habibi, Mohammad Hossein,Iravani, Mohammad Reza
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Read Online
- Selective Electrochemical Oxygenation of Alkylarenes to Carbonyls
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An efficient electrochemical method for benzylic C(sp3)-H bond oxidation has been developed. A variety of methylarenes, methylheteroarenes, and benzylic (hetero)methylenes could be converted into the desired aryl aldehydes and aryl ketones in moderate to excellent yields in an undivided cell, using O2 as the oxygen source and lutidinium perchlorate as an electrolyte. On the basis of cyclic voltammetry studies, 18O labeling experiments, and radical trapping experiments, a possible single-electron transfer mechanism has been proposed for the electrooxidation reaction.
- Li, Xue,Bai, Fang,Liu, Chaogan,Ma, Xiaowei,Gu, Chengzhi,Dai, Bin
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supporting information
p. 7445 - 7449
(2021/10/02)
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- Rhodium(III)-Catalyzed Aldehyde C?H Activation and Functionalization with Dioxazolones: An Entry to Imide Synthesis
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A rhodium(III)-based catalytic system has been used to develop a C?H bond activation of benzaldehyde derivatives and subsequent functionalization with dioxazolones in order to afford imides. The importance of the nature of the directing group to perform selectively the aldehydic C?H bond activation has been highlighted. The scope investigation showed that this transformation could be applied to various dioxazolones and many benzaldehyde derivatives as well as an acrolein derivative. Derivatization reactions of the imide products demonstrated the synthetic utility of this rhodium-catalyzed aldehydic C?H amidation.
- Bellière-Baca, Virginie,Clavier, Hervé,Hérault, Damien,Massouh, Joe,Petrelli, Antoine
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supporting information
(2022/01/06)
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- Synthesis and structure-activity relationship studies of hydrazide-hydrazones as inhibitors of laccase from trametes versicolor
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A series of hydrazide-hydrazones 1-3, the imine derivatives of hydrazides and aldehydes bearing benzene rings, were screened as inhibitors of laccase from Trametes versicolor. Laccase is a copper-containing enzyme which inhibition might prevent or reduce the activity of the plant pathogens that produce it in various biochemical processes. The kinetic and molecular modeling studies were performed and for selected compounds, the docking results were discussed. Seven 4-hydroxybenzhydrazide (4-HBAH) derivatives exhibited micromolar activity Ki = 24-674 μM with the predicted and desirable competitive type of inhibition. The structure-activity relationship (SAR) analysis revealed that a slim salicylic aldehyde framework had a pivotal role in stabilization of the molecules near the substrate docking site. Furthermore, the presence of phenyl and bulky tert-butyl substituents in position 3 in salicylic aldehyde fragment favored strong interaction with the substrate-binding pocket in laccase. Both 3- and 4-HBAH derivatives containing larger 3-tert-butyl-5-methyl- or 3,5-di-tert-butyl-2-hydroxy-benzylidene unit, did not bind to the active site of laccase and, interestingly, acted as non-competitive (Ki = 32.0 μM) or uncompetitive (Ki = 17.9 μM) inhibitors, respectively. From the easily available laccase inhibitors only sodium azide, harmful to environment and non-specific, was over 6 times more active than the above compounds.
- Giurg, Miros?aw,Maniak, Halina,Matyja, Konrad,Talma, Micha?,Trusek, Anna
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supporting information
(2020/03/23)
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- Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage-Independent Activation of Strong C-O Bonds
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Despite the prevalence of alcohols and carboxylic acids as functional groups in organic molecules and the potential to serve as radical precursors, C-O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen-centered nucleophile. We show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H atom trapping to afford the deoxygenated products. Using the same method, we demonstrate access to synthetically versatile acyl radicals, which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge C-O, C-N, and C-C bonds in a single step.
- Stache, Erin E.,Ertel, Alyssa B.,Rovis, Tomislav,Doyle, Abigail G.
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p. 11134 - 11139
(2018/11/21)
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- Synthesis and Characterization of meso-Substituted Cobalt Tetradehydrocorrin and Evaluation of Its Electrocatalytic Behavior Toward CO2 Reduction and H2 Evolution
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A meso-aryl substituted cobalt(II) tetradehydrocorrin complex (Co(II)TDHC) has been synthesized and investigated. The corrin framework, determined by X-ray crystallographic analysis, is found to be relatively planar except at the C1 and C19 positions. Cyclic voltammetry (CV) measurements indicate two positively shifted reversible redox couples at -0.53 and -1.70 V vs Fc/Fc+ for [CoII]+/[CoI] and [CoI]/([CoI]?- and/or [CoII]-) ([CoII] = Co(II)TDHC), respectively, compared with the previously reported cobalt porphyrin complex, because the tetradehydrocorrin ligand efficiently promotes the formation of low-valent metal species due to its monoanionic character. Furthermore, it is found that the current in the CV measurement is significantly enhanced upon addition of H2O under a CO2 atmosphere, indicating the progression of electroreductive catalysis by Co(II)TDHC. However, controlled-potential electrolysis (CPE) using Co(II)TDHC under the same conditions shows generation of H2 as a major product and only a small amount of CO as a CO2 reduction product; Faradaic efficiencies are calculated to be 66.8 and 4.5%, respectively. The CPE with a buffer solution under an N2 atmosphere reveals that the selective H2 generation is promoted by the moderate acidification of the solution under CO2 saturation conditions. The present study demonstrates that the significantly stabilized Co(I) species with the monoanionic ligand framework preferentially catalyzes the thermodynamically favored H2 evolution rather than CO2 reduction.
- Ogawa, Ayumu,Oohora, Koji,Hayashi, Takashi
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p. 14644 - 14652
(2018/12/13)
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- Exploring the Strength of the H-Bond in Synthetic Models for Heme Proteins: The Importance of the N?H Acidity of the Distal Base
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The distal hydrogen bond (H-bond) in dioxygen-binding proteins is crucial for the discrimination of O2with respect to CO or NO. We report the preparation and characterization of a series of ZnIIporphyrins, with one of three meso-phenyl rings bearing both an alkyl-tethered proximal imidazole ligand and a heterocyclic distal H-bond donor connected by a rigid acetylene spacer. Previously, we had validated the corresponding CoIIcomplexes as synthetic model systems for dioxygen-binding heme proteins and demonstrated the structural requirements for proper distal H-bonding to CoII-bound dioxygen. Here, we systematically vary the H-bond donor ability of the distal heterocycles, as predicted based on pKavalues. The H-bond in the dioxygen adducts of the CoIIporphyrins was directly measured by Q-band Davies-ENDOR spectroscopy. It was shown that the strength of the hyperfine coupling between the dioxygen radical and the distal H-atom increases with enhanced acidity of the H-bond donor.
- Alberti, Mariza N.,Polyhach, Yevhen,Tzirakis, Manolis D.,T?dtli, Laura,Jeschke, Gunnar,Diederich, Fran?ois
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supporting information
p. 10194 - 10202
(2016/07/19)
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- Formylation of electron-rich aromatic rings mediated by dichloromethyl methyl ether and TiCl4: Scope and limitations
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Here the aromatic formylation mediated by TiCl4 and dichloromethyl methyl ether previously described by our group has been explored for a wide range of aromatic rings, including phenols, methoxy- and methylbenzenes, as an excellent way to produce aromatic aldehydes. Here we determine that the regioselectivity of this process is highly promoted by the coordination between the atoms present in the aromatic moiety and those in the metal core.
- Ramos-Tomillero, Iván,Paradís-Bas, Marta,De Pinho Ribeiro Moreira, Ibério,Bofill, Josep María,Nicolás, Ernesto,Albericio, Fernando
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supporting information
p. 5409 - 5422
(2015/05/13)
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- Pinpoint-fluorinated phenanthrene synthesis based on C-F bond activation of difluoroalkenes Dedicated to Prof. Véronique Gouverneur on the occasion of her receipt of the 2014 ACS Award for Creative Work in Fluorine Chemistry.
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Treatment with a cationic palladium(II) catalyst promoted the Friedel-Crafts-type cyclization of 1,1-difluoro-1-alkenes bearing a biphenyl skeleton to afford regioselectively fluorinated (pinpoint-fluorinated) phenanthrenes via C-F bond activation. The obtained pinpoint-fluorinated phenanthrenes were observed to be organized by π-π and C-H?F interactions to exhibit columnar and layer structures in the solid state.
- Fuchibe, Kohei,Morikawa, Toshiyuki,Ueda, Ryu,Okauchi, Tatsuo,Ichikawa, Junji
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supporting information
p. 106 - 115
(2015/11/10)
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- The Key Role of the Nonchelating Conformation of the Benzylidene Ligand on the Formation and Initiation of Hoveyda-Grubbs Metathesis Catalysts
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Experimental studies of Hoveyda-Grubbs metathesis catalysts reveal important consequences of substitution at the 6-position of the chelating benzylidene ligand. The structural modification varies conformational preferences of the ligand that affects its exchange due to the interaction of the coordinating site with the ruthenium center. As a consequence, when typical S-chelated systems are formed as kinetic trans-Cl2 products, for 6-substituted benzylidenes the preference is altered toward direct formation of thermodynamic cis-Cl2 isomers. Activity data and reactions with tricyclohexylphosphine (PCy3) support also a similar scenario for O-chelated complexes, which display fast trans-Cl2?cis-Cl2 equilibrium observed by NMR EXSY studies. The presented conformational model reveals that catalysts, which cannot adopt the optimal nonchelating conformation of benzylidene ligand, initiate through a high-energy associative mechanism.
- Bieszczad, Bartosz,Barbasiewicz, Micha?
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supporting information
p. 10322 - 10325
(2015/07/07)
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- Rational design and synthesis of novel 2-(substituted-2H-chromen-3-yl)-5-aryl-1H-imidazole derivatives as an anti-angiogenesis and anti-cancer agent
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Based on earlier proven pharmacophore analogues of cancer a novel 2-(substituted-2H-chromen-3-yl)-5-aryl-1H-imidazoles (13-16) were rationally designed and synthesized by the reaction of chromene-3-carboxylic acids (10a-d) with substituted acyl bromides in the presence of TEA followed by refluxing with NH4OAc in toluene. Compounds 13-16 were screened in vitro for the inhibition of KRAS/Wnt and their anti-angiogenesis properties. Compound 16f has been identified as a potent anti-angiogenesis molecule, which can be considered as a new lead structure. The molecular docking analysis displayed the higher binding affinity of 16f with KRAS, Wnt and VEGF.
- Gudipudi, Gopinath,Sagurthi, Someswar R.,Perugu, Shyam,Achaiah,Krupadanam, G. L. David
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p. 56489 - 56501
(2015/02/05)
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- Enantioselective total synthesis of (-)-blennolide A
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Blennolide A can be synthesized through an enantioselective domino-Wacker/carbonylation/methoxylation reaction of 7 a with 96 % ee and an enantioselective Wacker oxidation of 7 b with 89 % ee. Further transformations led to the α,β-unsaturated ester (E)-17, which was subjected to a highly selective Michael addition, introducing a methyl group to give 18 a. After a threefold oxidation and an intramolecular acylation, the tetrahydroxanthenone 4 was obtained, which could be transformed into (-)-blennolide A (ent-1) in a few steps. Domino effect: An enantioselective domino-Wacker/carbonylation/methoxylation process and an enantioselective Wacker oxidation are the key steps in the first total synthesis of the fungal metabolite blennolide A (see scheme). Copyright
- Tietze, Lutz F.,Ma, Ling,Reiner, Johannes R.,Jackenkroll, Stefan,Heidemann, Sven
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supporting information
p. 8610 - 8614
(2013/07/26)
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- Probing dense packed limits of a hyperbranched polymer through ligand binding and size selective catalysis
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In the area of dendritic chemistry (hyperbranched polymers and dendrimers) it is often generalized that dendrimers are the molecule of choice for smart, selective, or technical applications involving encapsulation or controlled/selective environments. This is despite the fact that hyperbranched polymers (HBP)s are generally easier and cheaper to synthesize, making them more amenable to large-scale applications. Dendrimers have been successful in these applications by virtue of a dense packed or dense shell limit. This paper describes the synthesis of a series of narrowly dispersed HBPs possessing binding and catalytic cores with a high and uniform loading. Subsequent binding experiments clearly demonstrated the existence of a dense packed limit with respect to polymer molecular weight and ligand size. A series of catalytic experiments were also performed in an attempt to exploit these molecules and their dense packed limit to the area of shape/size selective catalysis - an area where dendrimers have previously been used with celebrated success. However, although we were able to show the existence of a dense packed limit, we were initially unable to demonstrate any selectivity based on substrate size or shape. Nevertheless, further studies into core branching motif and multiplicity eventually enabled us to obtain a series of HBPs capable of perturbing the shape/size selectivity of a simple oxidation reaction involving two alkenes. Specifically, we were able to demonstrate a 3.5-fold shift in chemoselectivity toward a smaller alkene of lower reactivity. These results compare favorably with those obtained using dendrimers and allow us to conclude that, with careful thought regarding core design, HBPs are indeed capable of being applied to technical/smart applications involving controlled and selective environments.
- Ellis, Adam,Twyman, Lance J.
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p. 7055 - 7074
(2013/09/24)
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- Synthesis of new bulky bis(pyrazolyl)methane carboxylate (heteroscorpionate) ligands and their complexes with iron, manganese and nickel
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Three new sterically demanding ligands based on the bispyrazolylacetic acid motif have been prepared and complexes with Fe(ii), Fe(iii), Ni(ii) and Mn(ii) have been synthesised and characterised. Single crystal X-ray structures are included for two of the ligands in the protonated form and ten other complexes. Additionally, a new general route to amide derivatives has been established, a range of amide derivatives synthesised and their coordination chemistry investigated. Only one metal complex was synthesised from the amide ligands, and was bound via the hydroxylamine groups in preference to the pyrazole and carboxylate donor set. The Royal Society of Chemistry 2012.
- Jones, Michael W.,Baldwin, Jack E.,Cowley, Andrew R.,Dilworth, Jonathan R.,Karpov, Alexei,Smiljanic, Nicolas,Thompson, Amber L.,Adlington, Robert M.
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p. 14068 - 14086
(2013/01/15)
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- Facile preparation of aromatic esters from aromatic bromides with ethyl formate or DMF and molecular iodine via aryllithium
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Various aromatic bromides were treated with n-BuLi and subsequently with ethyl formate, followed by the reaction with ethanol and molecular iodine in the presence of K2CO3 to provide the corresponding aromatic ethyl esters in good yields. Moreover, aromatic bromides could be transformed into the corresponding aromatic methyl esters in good yields by the treatment with n-BuLi and subsequently with DMF, followed by the reaction with methanol, molecular iodine, and K2CO3. Some aromatics could be also converted into the corresponding aromatic esters in good yields by the treatment with n-BuLi, and subsequently with ethyl formate or DMF, followed by the reaction with molecular iodine and K2CO3. The present reactions offer a novel route for the transition-metal-free, carbon-monoxide-free, and therefore environmentally benign one-pot conversion of aromatic bromides and aromatics into aromatic esters.
- Ushijima, Sousuke,Moriyama, Katsuhiko,Togo, Hideo
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experimental part
p. 4701 - 4709
(2012/07/28)
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- 7-alkyl-3-benzylcoumarins: A versatile scaffold for the development of potent and selective cannabinoid receptor agonists and antagonists
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A series of 7-alkyl-3-benzylcoumarins was designed, synthesized, and tested at cannabinoid CB1 and CB2 receptors in radioligand binding and cAMP accumulation studies. 7-Alkyl-3-benzylcoumarins were found to constitute a versatile scaffold for obtaining potent CB receptor ligands with high potency at either CB1 or CB2 and a broad spectrum of efficacies. Fine-tuning of compound properties was achieved by small modifications of the substitution pattern. The most potent compounds of the present series include 5-methoxy-3-(2-methylbenzyl)-7-pentyl-2H-chromen-2-one (19a, PSB-SB-1201), a selective CB1antagonist (Ki CB 1 0.022 μM), 5-methoxy-3-(2-methoxybenzyl)-7-pentyl-2H-chromen-2- one (21a, PSB-SB-1202), a dual CB1/CB2agonist (CB 1Ki 0.032 μM, EC50 0.056 μM; CB 2Ki 0.049 μM, EC50 0.014 μM), 5-hydroxy-3-(2-hydroxybenzyl)-7-(2-methyloct-2-yl)-2H-chromen-2-one (25b, PSB-SB-1203), a dual CB1/CB2 ligand that blocks CB 1 but activates CB2 receptors (CB1Ki 0.244 μM; CB2Ki 0.210 μM, EC50 0.054 μM), and 7-(1-butylcyclopentyl)-5-hydroxy-3-(2-hydroxybenzyl)-2H-chromen-2- one (27b, PSB-SB-1204), a selective CB2 receptor agonist (CB 1Ki 1.59 μM; CB2Ki 0.068 μM, EC50 0.048 μM).
- Rempel, Viktor,Volz, Nicole,Hinz, Sonja,Karcz, Tadeusz,Meliciani, Irene,Nieger, Martin,Wenzel, Wolfgang,Br?se, Stefan,Müller, Christa E.
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p. 7967 - 7977
(2012/11/07)
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- A conductive paste for the conductive paste and metal powder
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A metal powder for a conductive paste has an average particle diameter D50 not greater than 5 mum and an X value defined by equation (1) not greater than 0.5: X value=D50 (mum)/BET specific surface area (m2/g) (1) The metal powder for a conductive paste is particularly preferable when wart-like projections of a diameter not greater than 150 nm are present on the particle surfaces. Typical types of the metal powder include Cu, Ag, Au, Pd, Pt, Ni, Al and alloys thereof. The metal powder for a conductive paste enables fabrication of a conductor having a low void ratio after the paste is fired.
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- Solvent-free oxidation of alcohols with potassium persulphate in the presence of bronsted acidic ionic liquids
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An efficient conversion of alcohols to aldehydes was achieved using potassium persulphate and 3-methylimidazolinium methane sulfonate. Copyright Taylor & Francis Group, LLC.
- Chaskar,Bhandari,Patil,Sharma,Mayeker
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experimental part
p. 366 - 370
(2009/04/07)
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- Very high rate enhancement of benzyl alcohol oxidation by an artificial enzyme
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(Figure Presented) Promoting the atomic dialogue! At neutral pH and ambient temperature, a cyclodextrin-derived ketone causes hydrogen peroxide and benzyl alcohols to meet in its active site and react up to 60 000 times faster than they do outside the cyclodextrin.
- Marinescu, Lavinia G.,Bols, Mikael
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p. 4590 - 4593
(2007/10/03)
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- A scaleable synthesis of fiduxosin
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Fiduxosin (1) has been under development at Abbott Laboratories for the treatment of benign prostatic hyperplasia. A convergent strategy required methodologies for preparation of an enantiomerically pure 3,4-cis-disubstituted pyrrolidine and a 2,3,5-trisubstituted thienopyrazine in a regiospecific manner. A [3+2] cycloaddition of an enantiopure azomethine ylide followed by a diastereoselective crystallization was employed to prepare the benzopyranopyrrolidine in high diastereomeric and enantiomeric purity. Conditions for reduction of an O-aryl lactone susceptible to epimerization were developed, and cyclization of the alcohol/phenol to the ether was accomplished in high yield. The thienopyrazine was prepared by condensation of methyl thioglycolate and a regiospecifically prepared 2-bromo-3-cyano-5-phenylpyrazine. Conditions for effective halogen substitutive deamination to prepare regiospecific trisubstituted pyrazines will be described.
- Haight, Anthony R.,Bailey, Anne E.,Baker, William S.,Cain, Michael H.,Copp, Richard R.,Demattei, John A.,Ford, Kelley L.,Henry, Rodger F.,Hsu, Margaret C.,Keyes, Robert F.,King, Steven A.,McLaughlin, Maureen A.,Melcher, Laura M.,Nadler, William R.,Oliver, Patricia A.,Parekh, Shyamal I.,Patel, Hemant H.,Seif, Louis S.,Staeger, Mike A.,Wayne, Gregory S.,Wittenberger, Steven J.,Zhang, Weijiang
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supporting information
p. 897 - 902
(2013/09/03)
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- Method for orthometalation of a carbocyclic aromatic derivative bearing at least an electron donor group
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The invention concerns a method for orthometalation of a carbocyclic aromatic derivative bearing at least an electron donor group, characterised in that it consists in reacting said carbocyclic aromatic derivative with an efficient amount of at least one alkaline metal in the presence of a compound of formula (I): RX, wherein: R represents a hydrocarbon radical having 1 to 20 carbon atoms which can be a saturated or unsaturated, linear or branched, acyclic aliphatic radical; a saturated or unsaturated, monocyclic or polycyclic cycloaliphatic radical; a saturated or unsaturated, linear or branched aliphatic radical bearing a cyclic substituent; and X represents a bromine or chlorine atom.
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(2010/01/31)
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- Probing the reactivity of photoinitiators for free radical polymerization: Time-resolved infrared spectroscopic study of benzoyl radicals
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A series of substituted benzoyl radicals has been generated by laser flash photolysis of α-hydroxy ketones, α-amino ketones, and acyl and bis(acyl)phosphine oxides, all of which are used commercially as photoinitiators in free radical polymerizations. The benzoyl radicals have been studied by fast time-resolved infrared spectroscopy. The absolute rate constants for their reaction with n-butylacrylate, thiophenol, bromotrichloromethane and oxygen were measured in acetonitrile solution. The rate constants of benzoyl radical addition to n-butylacrylate range from 1.3 x 105 to 5.5 x 105 M-1 s-1 and are about 2 orders of magnitude lower than for the n-butylacrylate addition to the counterradicals that are produced by α-cleavage of the investigated ketones. Density functional theoretical calculations have been performed in order to rationalize the observed reactivities of the initiating radicals. Calculations of the phosphorus-centered radicals generated by photolysis of an acyl and bis(acyl)phosphine oxide suggest that P atom Mulliken spin populations are an indicator of the relative reactivities of the phosphorus-centered radicals. The α-cleavage of (2,4,6-trimethylbenzoyl)phosphine oxide was studied by picosecond pump-probe and nanosecond step-scan time-resolved infrared spectroscopy. The results support a mechanism in which the α-cleavage occurs from the triplet excited state that has a lifetime less than or equal to the singlet excited state.
- Colley, Christopher S.,Grills, David C.,Besley, Nicholas A.,Jockusch, Steffen,Matousek, Pavel,Parker, Anthony W.,Towrie, Michael,Turro, Nicholas J.,Gill, Peter M. W.,George, Michael W.
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p. 14952 - 14958
(2007/10/03)
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- Synthesis and characterization of alkanethiolate-coordinated iron porphyrins and their dioxygen adducts as models for the active center of cytochrome p450: Direct evidence for hydrogen bonding to bound dioxygen
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Two kind of novel cytochrome P450 models, which have alkanethiolate axial ligands and hydroxyl groups inside molecular cavities, were designed and synthesized as functional O2 binding systems. A superstructured porphyrin, designated as "twin-coronet" porphyrin, was used as the common framework of the model complexes. This porphyrin bears four binaphthalene bridges on the both sides and forms two pockets surrounded by the bulky aromatic rings. Thiobenzyloxy and thioglycolate moieties, which contain an alkanethiolate group exhibiting various electron-donating abilities and degrees of bulkiness, were covalently linked to twin-coronet porphyrin to yield thiolate-coordinated hemes, TCP-TB and TCP-TG (twin-coronet porphyrin with thiobenzyloxy and thioglycolate groups), respectively. Both ferric complexes exhibited high stability during usual experimental manipulation under air and were characterized by MS, UV/vis, ESR spectroscopies, and CV. The ESR spectra exhibited low-spin signals (TCP-TB: g = 2.334, 2.210, 1.959; TCP-TG: g = 2.313, 2.209, 1.966). The cyclic voltammogram of TCP-TB in CH3CN gave a quasi-reversible wave which corresponds to the FeIII/FeII redox couple: Ep/2 = -1.35 V (vs Fc/Fc+). On the other hand, TCP-TG showed a fine reversible wave: E1/2 (FeIII/FeII) = -1.12 V. The stable dioxygen adducts were formed in the reaction of the ferric complexes with KO2 under an oxygen atmosphere and characterized by UV/vis and resonance Raman (RR) spectroscopies. In the RR spectra, the v(O-O) bands of the dioxygen adducts were observed at 1138 cm-1 (TCP-TB) and 1137 cm-1 (TCP-TG). The hypothesis that hydrogen bonding between the bound oxygen and the hydroxyl groups of the binaphthyl moieties could increase their stability was verified by RR spectroscopy. When all hydroxyl groups were deuterated, only the frequencies of the v(O-O) bands were upshifted by 2 cm-1 without any perturbation in the porphyrin skeleton. This work shows the first direct evidence for a hydrogen bond to dioxygen in an oxy form of a thiolate-coordinated heme model system. These results are discussed in context of the process of dioxygen binding and activation in cytochrome P450.
- Tani,Matsu-Ura,Nakayama,Ichimura,Nakamura,Naruta
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p. 1133 - 1142
(2007/10/03)
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- 3-Carboxypyridinium chlorochromate: An inexpensive and efficient reagent for cleavage of carbon-nitrogen double bonds under non-aqueous condition
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3-Carboxypyridinium chlorochromate (CPCC) is an inexpensive, easily prepared and stable reagent. With this reagent oximes, phenylhydrazones, p-nitrophenylhydrazones, semicarbazones and azines are converted to their corresponding carbonyl compounds in good to excellent yields.
- Baltork,Pouranshirvani
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- Synthesis and Characterization of a Membrane-Spanning Porphinatoiron(II)
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A new tetraphenylporphinatoiron(II) having a couple of four amphiphilic chains on both sides of the porphyrin ring plane, 5,10,15,20-tetra(2',6'-di(20''-hydroxy-2'',2''-dimethylicosanoyloxy)-phenyl)porphinatiron, was synthesized as a model for membrane intrinsic proteins.It was well incorporated in the liposomal bilayer and characterized.The complex with 1-dodecylimidazole embedded in phospholipid bilayer formed an oxygen adduct in water at 25 deg C.
- Tsuchida, Eishun,Hasegawa, Etsuo,Komatsu, Teruyuki,Nakata, Taisaku,Nishide, Hiroyuki
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p. 389 - 392
(2007/10/02)
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- Titanium- or Zirconium-Catalyzed Selective Dehydrogenation of Benzyl Alcohols to Aldehydes and Ketones with tert-Butyl Hydroperoxide
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Primary and secondary benzyl alcohols are selectively converted in high yields into the corresponding aldehydes or ketones using tert-butyl hydroperoxides and catalytic amounts of titanium or (better) zirconium alcoholates.Aliphatic hydroxy groups, double bonds (except those in allylic position to hydroxy groups), and phenolic hydroxy groups (except those in the ortho position to the benzylic alcohol) are not attacked.
- Krohn, Karsten,Khanbabaee, Karamali,Rieger, Hagen
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p. 1357 - 1364
(2007/10/02)
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- Regioselective Reductive Electrophilic Substitution of 1,2,3-Trimethoxybenzene and Its 5-Alkyl-Substituted Homologues
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The methoxy group in the 2-position of 1,2,3-trimethoxybenzene (1) can be regioselectively removed by electron transfer from alkali metals and replaced with a variety of electrophiles in a one-pot procedure, affording 2-substituted resorcinol dimethyl ethers.The usefulness of this synthetic method is illustrated by numerous examples.This reaction procedure has been successfully extended to the 5-methyl-substituted homologue (2), but limitations occur with the higher homologue 1-pentyl-3,4,5-trimethoxybenzene (3).Investigations on the mechanism of demethoxylation, with the aid of labeling experiments, provided clear evidence for the intermediacy of aryl radicals and explained the low yields obtained in the reductive electrophilic substitution of compound 3.
- Azzena, Ugo,Denurra, Teresa,Melloni, Giovanni,Piroddi, Anna Maria
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p. 5386 - 5390
(2007/10/02)
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- 3-METHOXYBENZYL (3-MPM) AND 3,5-DIMETHOXYBENZYL (3,5-DMPM) PROTECTING GROUPS FOR THE HYDROXY FUCTION LESS READILY REMOVABLE THAN 4-METHOXYBENZYL (MPM) AND 3,4-DIMETHOXYBENZYL (DMPM) PROTECTING GROUPS BY DDQ OXIDATION
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New protecting groups for the hydroxy fuction, 3-methoxybenzyl (3-MPM) and 3,5-dimethoxybenzyl (3,5-DMPM) groups are slowly removed by DDQ oxidation at room temperature and distinguished from readily removable 4-methoxybenzyl (MPM).They are stable to strong acids.KEYWORDS-- protecting group; hydroxy function; DDQ oxidation; selective deprotection; 3-methoxybenzyl; 3,5-dimethoxybenzyl
- Nakajima, Noriyuki,Abe, Reiko,Yonemitsu, Osamu
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p. 4244 - 4247
(2007/10/02)
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- THE 1,4-ADDITION OF SINGLET OXYGEN TO 2,6-DIMETHOXY-1-(2-METHOXYETHENYL)-BENZENE AND 2-METHOXY-1-(2-METHOXYETHENYL)NAPHTHALENE. THE 1,4-ENDO-PEROXIDES AS EQUIVALENTS OF 6-OXO-2,4-CYCLOHEXADIENYLIDENACETATES.
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The sensitized photooxygenation of vinylarenes 1 and 2 gave the corresponding 1,4-endoperoxides which were decomposed under mild conditions into quinone methides bearing ester function at the exocyclic carbon.
- Matsumoto, Masakatsu,Kuroda, Keiko,Suzuki, Yoshito
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p. 3253 - 3256
(2007/10/02)
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- The Chemistry of Fungi. Part 76. The Synthesis and Transformations of Three Steroisomeric 2-(2,6-Dimethoxybenzoyl)-3-methoxycarbonyl-7-oxabicycloheptanes
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Condensation of 1-lithio-2,6-dimethoxybenzene with the anhydride (10) of 7-oxabicycloheptane-2β,3β-dicarboxylic acid and subsequent esterification of the product gave 2β-(2,6-dimethoxybenzoyl)-3β-methoxycarbonyl-7-oxabicycloheptane (8; R1=H, R2=Me).The isomeric 2α-(2,6-dimethoxybenzoyl)-3α-methoxycarbonyl-7-oxabicycloheptane (11; R=Me) was prepared similarly using the anhydride (9) from 7-oxabicycloheptane-2α,3α-dicarboxylic acid.Epimerisation of (11; R=Me) or of (8; R1=H, R2=Me) gave 2α-(2,6-dimethoxybenzoyl)-3β-methoxycarbonyl -7-oxabicycloheptane (12).Treatment with boron trichloride of (11; R=Me) gave 1α-chloro-4β-hydroxy-2α-(2-hydroxy-6-methoxybenzoyl)-3α-methoxycarbonylcyclohexane (13; R=H) and 1,7α-dihydroxy-8β-methoxycarbonyl-5aα,5,6,7,8,8aα-hexahydroxanthone (23; R=H); similarly (8; R1=H, R2=Me) gave 4β-hydroxy-2β-(2-hydroxy-6-methoxybenzoyl)cyclohexane-1β,3β-carbolactone (24; R=H) and 1,7α-dihydroxy-8α-methoxycarbonyl-5aα,5,6,7,8,8aα-hexahydroxanthone (25; R=H).The third isomer (12) formed 4α-chloro-1β-hydroxy-2α-(2-hydroxy-6-methoxybenzoyl)-3β-methoxycarbonylcyclohexane (31; R=H) together with 1,7α-dihydroxy-8α-methoxycarbonyl-5aα,5,6,7,8,8aα-hexahydroxanthone (32; R=H).Hydrogenolysis of (1; R1=R2=Me) or treatment of (11; R=Me) with acid yielded 2-(2,6-dimethoxybenzoyl)-4β-hydroxy-3α-methoxycarbonylcyclohexene (15; R=H); the corresponding acetate (15; R=Ac) was hydroxylated to form 4β-acetoxy-2α-(2,6-dimethoxybenzoyl)-1β,2β-dihydroxy-3α-methoxycarbonylcyclohexane (18) as the major product.The steroisomeric cyclohexene (34; R=H) was similarly obtained.Bromination of the ketone (11; R=Me) gave the α-bromoketone (33): similarly the α-bromoketone (8; R1=Br, R2=Me) was obtained from (8; R1=H, R2=Me).Dehydrobromination of each of these bromoketones formed 2-(2,6-dimethoxybenzoyl)-3-methoxycarbonyl-7-oxabicyclohept-2-ene (1, R1=R2=Me).Various further transformations of these products are described.
- Borthwick, Alan D.,Curry, David J.,Poynton, Alan,Whalley, W. Basil,Hooper, John W.
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p. 2435 - 2444
(2007/10/02)
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