- Direct conversion of chiral cyanohydrins to chiral nitrones by transimination
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A new method for the preparation of enantiomerically pure N-benzyl nitrones is described. By using either a one-pot reduction-transimination or a one-pot Grignard addition-transimination sequence chiral O-protected α-hydroxynitriles can be converted into chiral aldo- and ketonitrones, respectively.
- Hulsbos, Edith,Marcus, Jan,Brussee, Johannes,Van der Gen, Arne
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Read Online
- Boronic Acid Mediated Coupling of Catechols and N-Hydroxylamines: A Bioorthogonal Reaction to Label Peptides
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An irreversible, three-component assembly with 2-formylphenylboronic acid, catechol, and N-hydroxylamines was achieved in aqueous media. The boronate ester product was formed with substituted catechols including l-DOPA. Assembly was found to be orthogonal to common biological functional groups and both copper(I)-catalyzed alkyne-azide cycloaddition and aminoether/carbonyl condensations. Boronate ester formation and aminoether condensation were achieved in one pot with a hexameric peptide.
- Meadows, Margaret K.,Roesner, Emily K.,Lynch, Vincent M.,James, Tony D.,Anslyn, Eric V.
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Read Online
- Sc(OTf)3-catalyzed [3 + 2]-cycloaddition of nitrones with ynones
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An efficient approach to access functionalized (2,3-dihydroisoxazol-4-yl) ketones has been developed by reacting nitrones 4 with ynones 7 or terminal ynones 10 in a one-pot fashion. The reaction went through a formal Sc(OTf)3-catalyzed [3 + 2]-cycloaddition process to generate a number of functionalized (2,3-dihydroisoxazol-4-yl) ketones 11aa-11aw, 11ba-11la and 12aa-12ae in moderate to good yields. This journal is
- He, Chun-Ting,Han, Xiao-Li,Zhang, Yan-Xue,Du, Zhen-Ting,Si, Chang-Mei,Wei, Bang-Guo
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p. 457 - 466
(2021/01/29)
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- Chemoselective and Site-Selective Reductions Catalyzed by a Supramolecular Host and a Pyridine-Borane Cofactor
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Supramolecular catalysts emulate the mechanism of enzymes to achieve large rate accelerations and precise selectivity under mild and aqueous conditions. While significant strides have been made in the supramolecular host-promoted synthesis of small molecules, applications of this reactivity to chemoselective and site-selective modification of complex biomolecules remain virtually unexplored. We report here a supramolecular system where coencapsulation of pyridine-borane with a variety of molecules including enones, ketones, aldehydes, oximes, hydrazones, and imines effects efficient reductions under basic aqueous conditions. Upon subjecting unprotected lysine to the host-mediated reductive amination conditions, we observed excellent ?-selectivity, indicating that differential guest binding within the same molecule is possible without sacrificing reactivity. Inspired by the post-translational modification of complex biomolecules by enzymatic systems, we then applied this supramolecular reaction to the site-selective labeling of a single lysine residue in an 11-amino acid peptide chain and human insulin.
- Morimoto, Mariko,Cao, Wendy,Bergman, Robert G.,Raymond, Kenneth N.,Toste, F. Dean
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p. 2108 - 2114
(2021/02/06)
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- TRICYCLIC INHIBITORS OF HEPATITIS B VIRUS
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The present invention relates to compounds that are inhibitors of hepatitis B virus (HBV). Compounds of this invention are useful alone or in combination with other agents for treating, ameliorating, preventing or curing HBV infection and related conditions. The present invention also relates to pharmaceutical compositions containing said compounds.
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Page/Page column 54; 56
(2020/03/02)
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- Indazole compounds and application thereof to preparation of IDO inhibitors
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The invention discloses indazole compounds as shown in a formula (i) or (II) which is described in the specification, and a preparation method thereof, and application of the compounds as IDO inhibitors. The compounds provided by the invention can be used for preventing and/or treating a plurality of diseases, such as Alzheimer's disease, cataract, infections related to cellular immune activation,autoimmune diseases, AIDS, cancers, depression, the metabolic disorder of tryptophan or the like.
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- Chemoselective Synthesis of Amines from Ammonium Hydroxide and Hydroxylamine in Continuous Flow
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The chemoselective amination of alkyl bromides and chlorides with aqueous ammonia and hydroxylamine was achieved in continuous flow to produce primary ammonium salts and hydroxylamines in high yields. An in-line workup was designed to isolate the corresponding primary amine, which was also telescoped in further reactions, such as acylation and Paal-Knorr pyrrole synthesis. Monosubstituted epoxides are also compatible with the reaction conditions.
- Audubert, Clément,Bouchard, Alexanne,Mathieu, Gary,Lebel, Hélène
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p. 14203 - 14209
(2019/01/21)
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- Synthesis and characterization of N-methyl and N-benzyl cinnamohydroxamic acids
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N-methyl and N-benzyl cinnamohydroxamic acid was prepared by coupling reaction between N-methyl hydroxylamine and N-benzyl hydroxylamine with cinnamoyl chloride. The compounds were structurally characterized with 1H NMR, IR and elemental analysis.
- Rajput, Surendra K.,Patel, Anita,Bapat, Kishor N.
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p. 885 - 887
(2017/02/10)
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- SUBSTITUTED PYRROLIDINE COMPOUNDS
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The present disclosure provides substituted pyrrolidine compounds having Formula (I): and the pharmaceutically acceptable salts and solvates thereof, wherein R1, B, X, and Z are defined as set forth in the specification. The present disclosure is also directed to the use of compounds of Formula (I) to treat a disorder responsive to the blockade of SMYD proteins such as SMYD3 or SMYD2. Compounds of the present disclosure are especially useful for treating cancer.
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- The peculiar behavior of Picha in the formation of metallacrown complexes with Cu(ii), Ni(ii) and Zn(ii) in aqueous solution
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The thermodynamic stability of the metallacrown complexes formed by picolinehydroxamic acid (Picha) with Cu(ii), Ni(ii) and Zn(ii) in aqueous solution has been determined by potentiometry, and the speciation models were validated by ESI-MS and UV-visible spectrophotometry. Cu(ii) and Zn(ii) form 12-MC-4 species as the unique metallacrowns present in the solution. While for Cu(ii) the 12-MC-4 is slightly less stable than that obtained with alaninehydroxamic acid (Alaha), the opposite was found for Zn(ii). Moreover, with Cu(ii) unprecedented 15-MC-5 and 18-MC-6 species were identified under ESI-MS conditions. Picha with Ni(ii) forms, in contrast, a 15-MC-5 complex as a unique metallacrown species. Structural studies of the framework of the 12-MC-4 complexes by ab initio methods were also carried out. The results of our investigations allowed us to rationalize not only the different behaviour of Picha in the formation of metallacrowns with the three metal ions, but also the reasons which underpin the strategies for stabilization of these species reported in the literature using ancillary ligands such as pyridine. This journal is
- Marchi, Luciano,Marchetti, Nicola,Atzeri, Corrado,Borghesani, Valentina,Remelli, Maurizio,Tegoni, Matteo
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p. 3237 - 3250
(2015/03/05)
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- O-trifluoromethylation of N,N-disubstituted hydroxylamines with hypervalent iodine reagents
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A mild trifluoromethylation reaction of N,N-disubstituted hydroxylamines that is tolerant towards a variety of functional groups, including nitriles, alcohols, ketones, esters, amides, imides, and nitrogen heterocycles, is reported. The key feature of this reaction is the activation of the CF 3 reagent with either trimethylsilyl triflate or LiClO4 and partial or full deprotonation of the substrate with tetramethylguanidine or lithium diisopropylamide. Products were obtained in up to 80 % yield. Preliminary mechanistic studies suggested that the reaction follows a radical pathway in which the deprotonated hydroxylamine and a Lewis or Bronsted acid activated CF3 reagent engages in a single-electron-transfer step to generate a pair of radicals that recombine to afford the desired product. The trifluoromethylation procedure was successfully used in the modification of secondary nitrogen groups of pharmaceutically relevant targets (Fluoxetine and Mefloquine), which afforded new derivatives containing a novel N-trifluoromethoxy moiety. Copyright
- Matousek, Vaclav,Pietrasiak, Ewa,Sigrist, Lukas,Czarniecki, Barbara,Togni, Antonio
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supporting information
p. 3087 - 3092
(2014/06/09)
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- One-pot synthesis of dihydrobenzisoxazoles from hydroxylamines, acetylenedicarboxylates, and arynes via in situ generation of nitrones
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Aryne [3 + 2] cycloaddition with nitrones generated in situ from the addition of hydroxylamines to acetylenedicarboxylates affords moderate to good yields of dihydrobenzisoxazoles. This reaction extends the current scope of aryne cycloaddition to include in situ generated nitrones and produces functionalized dihydrobenzisoxazoles with a quaternary center.
- Li, Pan,Wu, Chunrui,Zhao, Jingjing,Li, Yang,Xue, Weichao,Shi, Feng
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- Synthesis and cytotoxic evaluation of novel platinum(II) complexes with C2-asymmetric and C2-symmetric chiral vicinal diamines
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A series of new platinum(II) complexes with C2-asymmetric and C2-symmetric 1,2-diamines were designed and synthesized by convenient methods, involving samarium diiodide induced reductive coupling as the key step. The results of cytotoxicity showed that compounds (R,R)-11a and (S,S)-11a, two novel platinum(II) complexes with asymmetric 1,2-diamines, exhibited more potent cytotoxicity than that of oxaliplatin against all leukemia cell lines. Interestingly, (R,R)-11a and (S,S)-11a demonstrated less potent activity against three solid cancer cell lines than that of oxaliplatin, which indicated that these two compounds may only selectively inhibit the leukemia cell lines. In contrast, (R,R)-15a and (S,S)-15a, two platinum(II) complexes with symmetric 1,2-diamines, showed similar cytotoxicity to that of oxaliplatin against all leukemia cell lines and more potent activity against solid cancer cell lines. Further flow cytometry data indicated that (R,R)-11a could obviously arrest leukemia K562 cells in G2/M phases. A series of new platinum(II) complexes with C2-asymmetric and C2-symmetric 1,2-diamines were designed and synthesized by convenient methods, involving samarium diiodide induced reductive coupling as the key step. The cytotoxicity of these analogs against four leukemia and three solid cancer cell lines was evaluated and the preliminary structure-activity relationship is also discussed. Flow cytometry data indicated that (R,R)-11a could obviously arrest leukemia K562 cells in G2/M phases. Copyright
- Zhang, Chen,Liu, Hongrui,Yang, Qing,Chang, Jun,Sun, Xun
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p. 154 - 158
(2013/08/24)
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- Oxyazapeptides: Synthesis, structure determination, and conformational analysis
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Herein we report the synthesis, X-ray structure determination, and conformational analysis of a novel class of heteroatom-modified peptidomimetics, which we shall call "oxyazapeptides". Substituting the typical native N-Cα bond with an O-Nα bond creates a completely new, previously unknown family of peptidomimetics, which are hydrolytically stable and display very interesting conformational behavior. Force field calculations revealed that the barrier to rotation around the O-Nα bond in oxyazapeptides is five times lower than that around the N-Nα bond in azapeptides. Also, conformational analysis supported by X-ray suggests that the oxyaza moiety can effectively induce β-turns, which can make the newly discovered oxyazapeptide scaffold a useful tool for drug discovery and for design of biologics.
- Biswas, Suvendu,Abo-Dya, Nader E.,Oliferenko, Alexander,Khiabani, Amir,Steel, Peter J.,Alamry, Khalid A.,Katritzky, Alan R.
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p. 8502 - 8509
(2013/09/24)
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- A magnetoclick imidazolidinone nanocatalyst for asymmetric 1,3-dipolar cycloadditions
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A 1,3-dipolar azide-alkyne cycloaddition has been used to prepare a magnetic nanoparticle immobilized MacMillan catalyst that catalyzes the enantioselective 1,3-dipolar cycloaddition between nitrones and α,β-unsaturated aldehydes. The catalyst can be recovered and recycled for five consecutive runs without any significant loss in yields and diastereo- and enantioselectivities of the isoxazolidines. Copyright
- Pagoti, Sreenivasarao,Dutta, Debasish,Dash, Jyotirmayee
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p. 3532 - 3538
(2014/01/06)
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- Highly enantioselective intermolecular hydroamination of allylic amines with chiral aldehydes as tethering catalysts
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Chirally LinkedIn: Chiral aldehydes are effective tethering catalysts for enantioselective intermolecular hydroamination, which provides access to vicinal diamine motifs in good yields and excellent enantioselectivities (see scheme). This work highlights simple chiral α-oxygenated aldehydes as effective organocatalysts capable of efficiently inducing asymmetry through transient intramolecularity. Copyright
- MacDonald, Melissa J.,Hesp, Colin R.,Schipper, Derek J.,Pesant, Marc,Beauchemin, André M.
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supporting information
p. 2597 - 2601
(2013/03/14)
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- Catalysis through temporary intramolecularity: Mechanistic investigations on aldehyde-catalyzed cope-type hydroamination lead to the discovery of a more efficient tethering catalyst
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Mechanistic investigations on the aldehyde-catalyzed intermolecular hydroamination of allylic amines using N-alkylhydroxylamines are presented. Under the reaction conditions, the presence of a specific aldehyde catalyst allows formation of a mixed aminal intermediate, which permits intramolecular Cope-type hydroamination. The reaction was determined to be first-order in both the aldehyde catalyst (α-benzyloxyacetaldehyde) and the allylic amine. However, the reaction displays an inverse order behavior in benzylhydroxylamine, which reveals a significant off-cycle pathway and highlights the importance of an aldehyde catalyst that promotes a reversible aminal formation. Kinetic isotope effect experiments suggest that hydroamination is the rate-limiting step of this catalytic cycle. Overall, these results enabled the elaboration of a more accurate catalytic cycle and led to the development of a more efficient catalytic system for alkene hydroamination. The use of 5-10 mol % of paraformaldehyde proved more effective than the use of 20 mol % of α-benzyloxyacetaldehyde, leading to high yields of intermolecular hydroamination products within 24 h at 30 °C.
- Guimond, Nicolas,MacDonald, Melissa J.,Lemieux, Valerie,Beauchemin, Andre M.
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supporting information
p. 16571 - 16577,7
(2020/09/15)
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- Towards the synthesis of 1-deoxy-1-nitropiperidinoses
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In the course of the first of several attempts to elaborate methods for the synthesis of 1-nitropiperidinoses, lincosamine was transformed into lactam 6 via hemiacetal 1, lactone 2, amide 3, oxo amide 4, and its cyclic tautomer 5. Treatment of the N-Boc-protected lactam oxime 9, obtained from lactam 6, with brominating agents failed to provide the bromonitroso carbamate 10. The N-Boc-protected lactam 13 derived from 6 was reduced to hemiacetal 14, but the corresponding N-Boc-aminooxime did not tautomerise to the C(1)-hydroxylamine, and nitrone 17, a potential precursor of the nitropiperidine 12, was not formed. Oxidation of the anomeric azide 20 with HOF·MeCN failed to provide the expected nitropiperidine 21. The phosphinimines 22 derived from 20 did not react with O3. In the next approach to 1-nitropiperidinoses, we treated the N-Boc-protected hemiacetal 25, obtained from the known gluconolactam 23 with N-benzylhydroxylamine. The resulting nitrone 26 exits in equilibrium with the anomeric N-benzyl-glycosylhydroxylamine that was oxidized to the anomeric nitrone 28. Ozonolysis of 28 led to the hemiacetal 25, resulting from the desired, highly reactive protected nitropiperidinose 29, that was evidenced by an IR band at 1561 cm-1. Similarly to the synthesis of nitrone 26, reaction of the N-tosyl-protected hemiacetal 31 with N-benzylhydroxylamine and oxidation provided the anomeric N-benzylhydroxylamines 33 via the p-toluenesulfonamido nitrone 32. Their oxidation with MnO2 led to the anomeric nitrone 34. Ozonolysis of 34 as evidenced by 1H-NMR and ReactIR spectroscopy led to the highly reactive nitropiperidinose 35. Like 29, 35 was transformed during workup, and only the hemiacetal 31 was isolated. The similarly prepared lincosamine-derived nitrone 17 was subjected to ReactIR-monitored ozonolysis that evidenced the formation of the protected nitropiperidinose 12, but only led to the isolation of 14. The facile transformation of the nitropiperidinoses to hemiacetals is rationalised by heterolysis of the anomeric C,N bond, recombination of the ion pair, and denitrosation of the resulting anomeric nitrite by a nucleophile. Attempts to convert the 1-deoxy-1-nitropiperidinose 35 to uloses 43 by base-catalysed Michael additions or Henry reactions were unsuccessful.
- Collin, Marie-Pierre,Vasella, Andrea
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experimental part
p. 2297 - 2317
(2011/02/18)
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- Cycloaddition of nitrones with arynes generated from benzobisoxadisilole or 2,3-naphthoxadisilole
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1,3-Dipolar cycloaddition of nitrones with arynes generated in situ from benzobisoxadisilole or 2,3-naphthoxadisilole afforded the oxadisilole fused benzo[d]isoxazoline or the naphtho[2,3-d]isoxazoline derivatives at room temperature in good yields.
- Wu, Kaicheng,Chen, Yali,Lin, Yibei,Cao, Weiguo,Zhang, Min,Chen, Jie,Lee, Albert W.M.
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experimental part
p. 578 - 582
(2010/09/05)
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- Intermolecular Cope-type hydroamination of alkenes and alkynes using hydroxylamines
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The development of the Cope-type hydroamination as a method for the metal- and acid-free intermolecular hydroamination of hydroxylamines with alkenes and alkynes is described. Aqueous hydroxylamine reacts efficiently with alkynes in a Markovnikov fashion to give oximes and with strained alkenes to give N-alkylhydroxylamines, while unstrained alkenes are more challenging. N-Alkylhydroxy-lamines also display similar reactivity with strained alkenes and give modest to good yields with vinylarenes. Electron-rich vinylarenes lead to branched products while electron-deficient vinylarenes give linear products. A beneficial additive effect is observed with sodium cyanoborohydride, the extent of which is dependent on the structure of the hydroxylamine. The reaction conditions are found to be compatible with common protecting groups, free OH and NH bonds, as well as bromoarenes. Both experimental and theoretical results suggest the proton transfer step of the N-oxide intermediate is of vital importance in the intermolecular reactions of alkenes. Details are disclosed concerning optimization, reaction scope, limitations, and theoretical analysis by DFT, which includes a detailed molecular orbital description for the concerted hydroamination process and an exhaustive set of calculated potential energy surfaces for the reactions of various alkenes, alkynes, and hydroxylamines.
- Moran, Joseph,Gorelsky, Serge I.,Dimitrijevic, Elena,Lebrun, Marie-Eve,Bedard, Anne-Catherine,Seguin, Catherine,Beauchemin, Andre M.
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supporting information; experimental part
p. 17893 - 17906
(2009/07/18)
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- Phase-transfer catalysis for the synthesis of hydroxylamines from oximes using benzyltriethylammonium borohydride in methanol and under solid-phase conditions
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Effective phase-transfer catalysis methodologies for the reduction of oximes to hydroxylamines by a selective and versatile reducing agent, benzyltriethylammonium borohydride (BTEABH), in methanol and under solid-phase conditions are presented.
- Gopalakrishnan, Mannathusamy,Anandabaskaran, Thirunavukkarasu,Sureshkumar, Purusothaman,Thanusu, Jayaraman,Kumaran, Arumugam K.,Kanagarajan, Vijayakumar
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- Enantioselective nitrone cycloadditions of α,β-unsaturated 2-acyl imidazoles catalyzed by bis(oxazolinyl)pyridine-cerium(IV) triflate complexes
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Enantioselective nitrone cycloadditions with β-substituted α,β-unsaturated 2-acyl imidazoles catalyzed by bis(oxazolinyl) pyridine-cerium(IV) triflate complexes 1 have been reported. The isoxazolidine products were efficiently transformed into densely functionalized β′-hydroxy-β-amino acid derivatives.
- Evans, David A.,Song, Hyun-Ji,Fandrick, Keith R.
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p. 3351 - 3354
(2007/10/03)
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- Reduction of 2,3-dihydroisoxazoles to β-amino ketones and β-amino alcohols
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(Chemical Equation Presented) We report the reduction of 2,3-dihydroisoxazoles to β-amino ketones and β-amino alcohols. The latter are obtained in high diastereoselectivity with preference for the syn isomer.
- Aschwanden, Patrick,Kvaerno, Lisbet,Geisser, Roger W.,Kleinbeck, Florian,Carreira, Erick M.
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p. 5741 - 5742
(2007/10/03)
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- Selective complexation of metals with isoxazolidine-containing fluorophores
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A series of 1,3-dipolar cycloaddition products of functionalized nitrones with 1,3-propene sultone and maleimide was synthesized through a multi-step scheme. Their fluorescent response to different metal ions was examined. Selective quenching of the fluorescent materials by Cu(II), Fe(III), and Ru(III) in acetonitrile was demonstrated, providing access to new chemosensor design for selected transition metals.
- Fang, Lei,Chan, Wing-Hong,He, Yong-Bing
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p. 173 - 176
(2007/10/03)
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- Non-covalent inhibitors of urokinase and blood vessel formation
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Novel compounds having activity as non-covalent inhibitors of urokinase and having activity in reducing or inhibiting blood vessel formation are provided. These compounds have P1 a group having an amidino or guanidino moiety or derivative thereof. These compounds are useful in vitro for monitoring plasminogen activator levels and in vivo in treatment of conditions which are ameliorated by inhibition of or decreased activity of urokinase and in treating pathologic conditions wherein blood vessel formation is related to a pathologic condition.
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- Novel peptides as NS3-serine protease inhibitors of hepatitis C virus
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The present invention discloses novel compounds which have HCV protease inhibitory activity as well as methods for preparing such compounds. In another embodiment, the invention discloses pharmaceutical compositions comprising such compounds as well as methods of using them to treat disorders associated with the HCV protease.
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- A ratiometric fluorescent sensor for Ag1 with high selectivity and sensitivity
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A bicyclic cycloadduct 1 bearing a pyrenyl moiety has been synthesized and investigated as a ratiometric fluorescent sensor for AgI. In an aqueous ethanol solution of 1, the presence of silver ion induces the formation of a 1:2 metal-ligand complex, which exhibits a strong intensity enhancement of the pyrene excimer emission at the expense of the emission of monomeric pyrene. Copyright
- Yang, Rong-Hua,Chan, Wing-Hong,Lee, Albert W. M.,Xia, Ping-Fang,Zhang, Hong-Kui,Li, Ke'An
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p. 2884 - 2885
(2007/10/03)
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- Non-covalent inhibitors of urokinase and blood vessel formation
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Novel compounds having activity as non-covalent inhibitors of urokinase and having activity in reducing or inhibiting blood vessel formation are provided. These compounds have Pi a group having an amidino or guanidino moiety or derivative thereof. These compounds are useful in vitro for monitoring plasminogen activator levels and in vivo in treatment of conditions which are ameliorated by inhibition of or decreased activity of urokinase and in treating pathologic conditions wherein blood vessel formation is related to a pathologic condition.
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- BF3-promoted hydrostannation of N-heteroatom-substituted imines for the reduction of C=N bond
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Hydrostannation of N-heteroatom-substituted imines such as oxime ethers, hydrazones, oximes, nitrones, and N-sulfonyl imines using a combination of Bu3SnH and BF3·OEt2 has been systematically studied. Not only aromatic aldimines but also kitimines and aliphatic imines were reduced to give the corresponding amines.
- Ueda, Masafumi,Miyabe, Hideto,Namba, Megumi,Nakabayashi, Toshiki,Naito, Takeaki
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p. 4369 - 4371
(2007/10/03)
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- Synthesis of N-substituted N-nitrosohydroxylamines as inhibitors of mushroom tyrosinase
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A series of N-substituted N-nitrosohydroxylamines including six new compounds were synthesized and examined for inhibition of mushroom tyrosinase. Corresponding hydroxylamines were reacted with n-butyl nitrite to give substituted nitrosohydroxylamines as their ammonium salt. The N-substituted hydroxylamines were prepared from the primary amines via the oxaziridine, or from the carbonyl compounds via the oxime. Most of the nitrosohydroxylamines tested inhibited mushroom tyrosinase. Among them, N-cyclopentyl-N-nitrosohydroxylamine exhibited the most potent activity (IC50=0.6 μM), as powerful as that of tropolone, one of the most powerful inhibitors. As removal of nitroso or hydroxyl moiety, the enzyme inhibitory activity was completely diminished. Both N-nitroso group and N-hydroxy group were suggested to be essential for the activity, probably by interacting with the copper ion at the active site of the enzyme. Lineweaver-Burk plotting showed that cupferron was a competitive inhibitor but that N-cyclopentyl-N-nitrosohydroxylamine was not.
- Shiino, Mitsuhiro,Watanabe, Yumi,Umezawa, Kazuo
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p. 1233 - 1240
(2007/10/03)
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- A survey of suitable protecting groups for the synthesis of hydroxylamines by Mitsunobu reactions
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A variety of protecting groups, commonly associated with peptide synthesis, are suitable for the N,O-protection of hydroxylamine; the resulting reagents are all suitable for N-alkylhydroxylamine synthesis using the Mitsunobu method.
- Knight, David W.,Leese, Mathew P.
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p. 2593 - 2595
(2007/10/03)
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- Butyltriphenylphosphonium tetraborate (BTPPTB) as a selective reducing agent for the reduction of imines, enamines and oximes and reductive alkylation of aldehydes or ketones with primary amines in methanol or under solid-phase conditions
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Butyltriphenylphosphonium tetraborate (BTPPTB) 1, generated as white solid from butyltriphenylphosphonium bromide and sodium borohydride, is found to be a selective and versatile reducing agent. The reagent in methanol or under solvent-free conditions is very useful for the reduction of imines, enamines and oximes or reductive amination of aldehydes and ketones. Under solvent-free conditions the reactions are faster and the yields of the products are higher.
- Hajipour,Mohammadpoor-Baltork,Noroallhi
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p. 152 - 156
(2007/10/03)
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- A novel transformation of primary amines to N-monoalkylhydroxylamines
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A novel transformation of primary amines to the corresponding N-monoalkylhydroxylamines is described. The three-step protocol involves selective mono-cyanomethylation of primary amines, regioselective formation of nitrones by m-CPBA oxidation, and hydroxylaminolysis of the nitrones with hydroxylamine hydrochloride. The method is applicable for a wide range of primary amines, including alkyl, benzyl, and chiral.
- Tokuyama,Kuboyama,Amano,Yamashita,Fukuyama
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p. 1299 - 1304
(2007/10/03)
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- Chelated complexes of paramagnetic metals with low toxicity
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Compounds of formulae (I) and (II) wherein the R, R1, R2, R3 and R4 groups have the meanings defined in the disclosure, are useful chelants for metal ions. The complexes of compounds (I) and (II) with paramagnetic ions are useful as contrast agents for M.R.I. imaging.
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- Asymmetric synthesis of β-amino acids by addition of chiral enolates to nitrones via N-acyloxyiminium ions
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N-Acyloxyiminium ions, generated by the reaction of nitrones with acyl halides, are highly reactive species and undergo facile reaction with a wide range of nucleophiles, such as ketene silyl acetals, titanium(IV) and boron enolates, hydrido- and allyltin(IV) reagents, and alkynyltitanium(IV) reagents, to give α-substituted amine derivatives. Optically active β-amino acids can be prepared by the reaction of N-acyloxyiminium ions with both boron and titanium(IV) enolates bearing chiral auxiliaries. Reversal of diastereoselectivity was observed by the reactions of the boron and titanium(IV) enolates. Using these reactions, all of the four stereoisomers of α-methyl-β-phenylalanines, for example, can be prepared highly diastereoselectively. Cyclic N-acyloxyiminium ions are useful for the asymmetric synthesis of pyrrolidine and piperidine alkaloids; (5R,8R,8aS)-5-cyano-8-methylindolizidine, which is a common key intermediate for synthesis of 5-substituted 8-methylindolizidines, was prepared selectively.
- Kawakami,Ohtake,Arakawa,Okachi,Imada,Murahashi
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p. 2423 - 2444
(2007/10/03)
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- Synthesis of 2,3-dihydroisoxazoles from propargylic N-hydroxylamines via Zn(II)-catalyzed ring-closure reaction
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(equation presented) A novel cyclization reaction of propargylic N-hydroxylamines to 2,3,5-trisubstituted 2,3-dihydroisoxazoles in the presence of catalytic amounts (10 mol %) of ZnI2 and DMAP is reported. The methodology provides a mild new approach to this useful class of substituted heterocycles that complements extant methods. The unique reactivity of the propargylic N-hydroxylamine substrates in the presence of Zn(II) and DMAP may have additional applications in other, related alkyne cyclization reactions.
- Aschwanden, Patrick,Frantz, Doug E.,Carreira, Erick M.
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p. 2331 - 2333
(2007/10/03)
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- 1-Benzyl-1-azonia-4-azabicyclo[2.2.2]octane tetrahydroborate (BAAOTB) as a selective reducing agent
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1-Benzyl-1-azonia-4-azabicyclo[2.2.2]octane tetrahydroborate (BAAOTB) 1 generated as white solid from commercially available DABCO and sodium borohydride is found to be a selective and versatile reducing agent. The reagent in t-butanol is very useful for reduction of imines, enamines, oximes, reductive amination of aldehydes and ketones and reductive methylation of amines.
- Hajipour,Mohammadpoor-Baltork,Rahi
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p. 239 - 242
(2007/10/03)
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- Chelated complexes of paramagnetic metals with low toxicity
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Compounds of formulae (I) and (II) wherein the R, R1, R2, R3and R4groups have the meanings defined in the disclosure, are useful chelants for metal ions. The complexes of compounds (I) and (II) with paramagnetic ions are useful as contrast agents for M.R.I. imaging.
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- Excess-acidity analysis for the acidic hydrolysis of some para-substituted N-benzylbenzohydroxamic acids
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The excess-acidity method has been applied to the hydrolysis reactions of some para substituted N-benzylbenzohydroxamic acids.X.C6H4C(O)N(OH).C6H5CH2 (X = H; p-CH3; p-NO2; p-F) in hydrochloric acid solutions in 10percent (v/v) dioxane water medium.The rate maxima observed are shown to be consistent with an A-2 mechanism.The mechanistic conclusions are fully supported by the activation parameters i.e. ΔH(excit.) and ΔS(excit.).
- Ghosh, Kallol K.,Ghosh, Sharmistha
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p. 315 - 319
(2007/10/02)
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- OXIDATION OF AMINES WITH 4a-FlEt-OOH: AN ENZYME MODEL OF FAD-CONTAINING MONOOXYGENASE
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Unlike the real enzyme, FAD-containing monooxygenase, 4a-FlEt-OOH, oxidizes most of common primary, secondary and tertiary water-soluble amines, such as N-methylmorpholine and n-octylamine.Both kinetic rates and products of the oxidation were obtained.The plots of rates vs. pKa values gave three different correlations lines depending upon the types of amines.
- Oae, Shigeru,Asada, Kaoru Ogawa,Yoshimura, Toshiaki,Fujimori, Ken
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p. 189 - 194
(2007/10/02)
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- N-NITROSOHYDROXYLAMINES I. ACETOLYSIS AND ACID-CATALYZED HYDROLYSIS OF N,O-DIBENZYL-N-NITROSOHYDROXYLAMINES. REACTION WITH POTASSIUM t-BUTOXIDE
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The major products of the hydrolysis of N,O-dibenzyl-N-nitrosohydroxylamines (3) are the denitrosated parent hydroxylamines (6); under more forcing conditions, products of the further hydrolysis of 6 are obtained.Acetolysis in acetic acid gives the benzyl acetates derived from both N- and O-substituents.With potassium tert-butoxide, the major path is abstraction of an O-benzyl hydrogen followed by fragmentation to the aldehyde and the benzyldiazotate ion.Possible mechanisms for the formation of the products are discussed.
- Kano, Kunio,Anselme, Jean-Pierre
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p. 10075 - 10086
(2007/10/02)
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- Synthesis and X-ray Analysis of Dihydro-1,2,4,5-trioxazine. Evidence of a Steowise Mechanism for the Cycloaddition of Carbonyl Oxides with Nitrones
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Carbonyl oxides, derived by ozonolysis of vinyl ethers, readily undergo cycloaddition reactions with nitrones affording dihydro-1,2,4,5-trioxazines in fair to excellent yield.The structures of dihydro-3,5,6-triphenyl-1,2,4,5-trioxazine (5f) and dihydro-3-cyclohexyl-5-methyl-6,6-diphenyl-1,2,4,5-trioxazine (5t) were unambiguously determined by X-ray analysis.Ozonolysis of 1-cyclohexyl-2-methoxyethene in the presence of either (E)- or (Z)-α-(4-methylphenyl)-α-phenyl-N-methylnitrone gave a 1:1 mixture of two stereoisomeric cycloadducts.This result, in conjunction with the structure of the relevant 5t, suggests that the cycloaddition proceeds by a stepwise mechanism.
- Mori, Mitsuyuki,Sugiyama, Tomohito,Nojima, Masatomo,Kusabayashi, Shigekazu,McCullough, Kevin J.
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p. 2285 - 2294
(2007/10/02)
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- Amino acid derivatives, and their production
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An amino acid derivative of the formula: STR1 wherein R1 is a protective group for hydroxyl, which is useful as an intermediate for production of antimicrobial agent.
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- Solvolysis of Benzyl Azoxytosylate and the Effect of Added Bases and Nucleophiles in Aqueous Trifluoroethanol and Aqueous Acetonitrile
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The rates and products of reaction of benzyl azoxytosylate (1b) in 1:1 (v/v) aqueous trifluoroethanol containing sodium perchlorate, sodium thiocyanate, sodium iodide, sodium bromide, sodium chloride, sodium hydroxide, sodium acetate, perchloric acid, and imidazole (buffered and unbuffered) have been measured at 42 deg C as part of an investigation into its mechanism of solvolysis.Nonbasic solutes give only small rate effects (some rate enhancing, others rate retarding), but, if nucleophilic, they lead to substitution products-the classic evidence of an SN1 reaction mechanism.After the initial rate-determining fragmentation, about half of the total solvolytic reaction proceeds through an electrophilic benzylic intermediate which is sufficiently long-lived to be trapped by nucleophilic solutes such as thiocyanate and the halide anions to give benzyl thiocyanate and benzyl halides.The other half gives the solvent-derived products benzyl alcohol and benzyl trifluoroethyl ether by a route which is not affected by dilute nonbasic solutes.Sodium acetate, which leads to negligible formation of benzyl acetate, and imidazole lead to the formation of trifluoroethyl tosylate; imidazole also produces N-tosylimidazole.These two base-induced bimolecular reactions involve nucleophilic attack at the sulfur of the tosyl group and involve electronic polarization of 1b in the opposite sense from that in the unimolecular fragmentation.One of the minor products in the presence of bases from the trappable intermediate of the solvolysis reaction is benzaldehyde, which suggests that the intermediate is C6H5CH2ON2+, a new type of reactive electrophile.It is not yet certain whether the half of the unimolecular fragmentation reaction which does not proceed through the trappable intermediate involves another electrophilic intermediate which is simply too short-lived to be intercepted by dilute nucleophiles or whether about half of the initial fragmentation is followed by a concerted uncoupled capture of the nascent benzyl cation by solvent.Replacing a small proportion of the trifluoroethanol in the reaction medium by the more nucleophilic ethanol does not have a drastic effect upon the overall course of the reaction, and a very similar mechanism also appears to be operative in aqueous acetonitrile.
- Maskill, H.,Jencks, William P.
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p. 2062 - 2070
(2007/10/02)
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- AN EFFICIENT SYNTHESIS OF N-MONOALKYLATED HYDROXYLAMINES
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A general method for the preparation of N-alkylated hydroxylamines from alkyl halides is reported.
- Doleschall, Gabor
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p. 2993 - 2994
(2007/10/02)
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- Amino acid derivative
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Derivatives having the general formula: STR1 in which the various radicals A,B,X,R1, R2, R3 and n have indicated definitions. These compounds have in particular enkephalinase-inhibiting, antalgic, antidepressive, antidiarrhea and hypotensive activities.
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- The Stereoselectivity of Addition of N-Benzyl-C-alkylnitrones to Methyl Crotonate. X-Ray Crystal Structure of (3RS,4SR,5RS)-2-Benzyl-4-methoxycarbonyl-5-methyl-3-isoxazolidine
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The addition of N-benzyl-C-alkyl- and N-benzyl-C-β-alkoxyalkyl-nitrones (1a-d) to methyl crotonate gave predominantly the 3,5-trans-substituted isoxazolidines (2a-d), selectivity ca. 3:1, whereas N-benzyl-C-α-alkoxyalkylnitrones (1e,f) gave more of the 3,5-cis-substituted isoxazolidines (3e,f) with selectivities of ca. 1:4. The chiral dimethyldioxolanyl nitrone (4) showed only modest diastereoface selectivity in its addition to methyl crotonate.However the more hindered tetramethyldioxolanyl nitrone (13) was more stereoselective, providing adduct (14) as the only significant product.The structure of this adduct was established by X-ray diffraction.
- Fray, M. Jonathan,Jones, Richard H.,Thomas, Eric J.
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p. 2753 - 2762
(2007/10/02)
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- Reaction of Sydnones with Oxygen
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The reaction of 3-benzyl- and 3-(p-chlorobenzyl)-4-phenylsydnones (1a and 1b) and of 3-benzylsydnone (1c) with oxygen at room temperature in the dark is described.Possible rationalizations for the formation of the products obtained are suggested.
- Nakajima, Masayuki,Anselme, Jean-Pierre
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p. 1444 - 1448
(2007/10/02)
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