- Direct conversion of azides and benzyl carbamates to t-butyl carbamates using polymethylhydrosiloxane and Pd-C
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One step direct conversion of azides and benzyl carbamates to t-butyl carbamales is achieved using inexpensive and safe hydride source namely polymethylhydrosiloxane (PMHS) under Pd-C catalysis.
- Chandrasekhar,Chandraiah,Raji Reddy,Venkat Reddy
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- Nitrogen-Doped Carbon Enables Heterogeneous Asymmetric Insertion of Carbenoids into Amines Catalyzed by Rhodium Nanoparticles
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Development of stable heterogeneous catalyst systems is a crucial subject to achieve sustainable society. Though metal nanoparticles are robust species, the study of asymmetric catalysis by them has been restricted because methods to activate metal nanopa
- Kobayashi, Shū,Masuda, Ryusuke,Yamashita, Yasuhiro,Yasukawa, Tomohiro
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supporting information
p. 12786 - 12790
(2021/05/07)
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- Carbon Dioxide-Mediated C(sp2)-H Arylation of Primary and Secondary Benzylamines
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C-C bond formation by transition metal-catalyzed C-H activation has become an important strategy to fabricate new bonds in a rapid fashion. Despite the pharmacological importance of ortho-arylbenzylamines, however, effective ortho-C-C bond formation of free primary and secondary benzylamines using PdII remains an outstanding challenge. Presented herein is a new strategy for constructing ortho-arylated primary and secondary benzylamines mediated by carbon dioxide (CO2). The use of CO2 with Pd is critical to allowing this transformation to proceed under relatively mild conditions, and mechanistic studies indicate that it (CO2) is directly involved in the rate-determining step. Furthermore, the milder temperatures furnish free amine products that can be directly used or elaborated without the need for deprotection. In cases where diarylation is possible, an interesting chelate effect is shown to facilitate selective monoarylation.
- Kapoor, Mohit,Chand-Thakuri, Pratibha,Young, Michael C.
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supporting information
p. 7980 - 7989
(2019/05/22)
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- Structure-based design of inhibitors of the aspartic protease endothiapepsin by exploiting dynamic combinatorial chemistry
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Structure-based design (SBD) can be used for the design and/or optimization of new inhibitors for a biological target. Whereas de novo SBD is rarely used, most reports on SBD are dealing with the optimization of an initial hit. Dynamic combinatorial chemistry (DCC) has emerged as a powerful strategy to identify bioactive ligands given that it enables the target to direct the synthesis of its strongest binder. We have designed a library of potential inhibitors (acylhydrazones) generated from five aldehydes and five hydrazides and used DCC to identify the best binder(s). After addition of the aspartic protease endothiapepsin, we characterized the protein-bound library member(s) by saturation-transfer difference NMR spectroscopy. Cocrystallization experiments validated the predicted binding mode of the two most potent inhibitors, thus demonstrating that the combination of de novo SBD and DCC constitutes an efficient starting point for hit identification and optimization. The dynamic duo: The combination of de novo structure-based design and dynamic combinatorial chemistry has been applied to the identification of novel acylhydrazone-based inhibitors for the aspartic protease endothiapepsin. 1H-STD-NMR spectroscopy has been used to identify the binders from the dynamic combinatorial libraries. Proposed binding modes of the most potent inhibitors have been confirmed by X-ray crystallography.
- Mondal, Milon,Radeva, Nedyalka,Koester, Helene,Park, Ahyoung,Potamitis, Constantinos,Zervou, Maria,Klebe, Gerhard,Hirsch, Anna K. H.
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supporting information
p. 3259 - 3263
(2014/04/03)
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- Synthesis of α-amino acid derivatives and peptides via enantioselective addition of masked acyl cyanides to imines
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A general, asymmetric synthesis of amino acid derivatives is reported. Masked acyl cyanide (MAC) reagents are shown to be effective umpolung synthons for enantioselective additions to N-Boc-aldimines. The reactions are catalyzed by a modified cinchona alkaloid, which can function as a bifunctional, hydrogen bonding catalyst, and afford adducts in excellent yields (90-98%) and high enantioselectivities (up to 97.5:2.5 er). Unmasking the addition products gives acyl cyanide intermediates that are intercepted by a variety of nucleophiles to afford α-amino acid derivatives. Notably, the methodology provides an alternative method for peptide bond formation.
- Yang, Kin S.,Rawal, Viresh H.
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supporting information
p. 16148 - 16151
(2015/02/02)
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- OXAZOLIDINONE COMPOUNDS AND DERIVATIVES THEREOF
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Compounds of Formula (I) and Formula (II) are useful inhibitors of tankyrase. Compounds of Formula (I) and Formula (II) have the following structure: where the definitions of the variables are provided herein.
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Paragraph 0429-0430
(2013/09/26)
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- Highly enantioselective reduction of β-amino nitroolefins with a simple n-sulfinyl urea as bifunctional catalyst
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Simple but effective: A structurally simple N-sulfinyl urea was found to be a highly efficient bifunctional catalyst, which allows for the development of a novel pathway for the construction of chiral β-amino nitroalkanes through enantioselective reduction of β-amino nitroolefins by trichlorosilane. High yields and excellent enantioselectivities were obtained for a broad range of β-arylamino nitroolefin substrates (see scheme). Copyright
- Liu, Xiang-Wei,Yan, Yan,Wang, Yong-Qiang,Wang, Chao,Sun, Jian
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supporting information; experimental part
p. 9204 - 9207
(2012/08/27)
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- Synthesis of arylglycine and mandelic acid derivatives through carboxylations of α-amido and α-acetoxy stannanes with carbon dioxide
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Incorporation reactions of carbon dioxide (CO2) with N-Boc-α-amido and α-acetoxy stannanes were developed using CsF as a mild tin activator. Monoprotected α-amido stannanes could be used, and the corresponding arylglycine derivatives were obtained in moderate-to-high yields under 1 MPa (10 atm) of CO2 pressure. α-Acetoxy stannanes also underwent carboxylation to afford mandelic acid derivatives in excellent yields under ambient CO2 pressure. Both transformations enabled the synthesis of α-tertiary and α-quaternary carboxylic acid derivatives. In addition, the chirality of (S)-N-tert-butylsulfonyl-α- amido stannanes was transferred with up to 90% inversion of configuration at 100 °C.
- Mita, Tsuyoshi,Sugawara, Masumi,Hasegawa, Hiroyuki,Sato, Yoshihiro
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scheme or table
p. 2159 - 2168
(2012/06/01)
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- ZnO nanorods as an efficient and heterogeneous catalyst for N-Boc protection of amines and amine derivatives
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An efficient ZnO nano catalyst, which was readily prepared from Zn(CH3CO2)2, 2H2O and PVP by a chemical solution approach has successfully catalyzed N-tertbutoxy carbonylation of amines. The ZnO nanorods were successful and gave promising results for highly active and chemoselective as well as easily recyclable catalyst for the NBoc protection reaction of a wide variety of amines. The catalyst could be easily recycled for five times without noticeable decrease in catalytic activity. The ZnO nanocatalyst was characterized with XRD and SEM.
- Nouria, Azita,Akbari, Jafar,Heydaric, Akbar,Nouri, Arezu
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experimental part
p. 38 - 42
(2012/05/04)
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- Asymmetric Ni-H insertion reaction cooperatively catalyzed by rhodium and chiral spiro phosphoric acids
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So near so SPA: Achiral dirhodium(II) carboxylates and chiral spiro phosphoric acids (SPA) cooperatively catalyzed asymmetric Ni-H insertion reactions with high enantioselectivity, high yields, and fast reaction rates at low catalyst loading (see scheme;
- Xu, Bin,Zhu, Shou-Fei,Xie, Xiu-Lan,Shen, Jun-Jie,Zhou, Qi-Lin
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supporting information; experimental part
p. 11483 - 11486
(2012/01/11)
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- Thioglycoluril as a highly efficient, recyclable and novel organocatalyst for N-Boc protection of amines
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A simple and efficient protocol for the chemoselective mono-N-Boc protection of various structurally diverse amines with di-tert-butyl dicarbonate using thioglycoluril as the catalyst is described. The catalyst can be readily separated from the reaction products by simple filtration and recovered for reuse. No competitive side reactions, such as formation of isocyanate, urea, oxazolidinone, and N,N-di-Boc derivatives were observed.
- Khaksar, Samad,Vahdat, Seyed Mohammad,Tajbakhsh, Mahmood,Jahani, Fatemeh,Heydari, Akbar
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experimental part
p. 6388 - 6391
(2011/01/03)
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- Protic ionic liquid [TMG][Ac] as an efficient, homogeneous and recyclable catalyst for Boc protection of amines
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An efficient and practical protocol for the chemoselective N-Boc protection of various structurally different aryl, aliphatic and heterocyclic amines was carried out with (Boc)2O using protic 1, 1, 3, 3-tetra-methylguanidinium acetate (10 mol%) as recyclable catalyst under solvent free condition at ambient temperature. No competitive side reactions (isocyanate, urea and N, N-di-Boc) were observed. α-Amino alcohols afforded the N-Boc-derivative without oxazolidinone formation.
- Akbari, Jafar,Heydari, Akbar,Ma'mani, Leila,Hassan Hosseini, Seyed
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experimental part
p. 544 - 547
(2010/11/05)
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- A practical synthesis of optically active arylglycines via catalytic asymmetric Strecker reaction
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A practical procedure for catalytic asymmetric synthesis of optically active arylglycine derivatives via optically active α-aminonitriles has been developed. The N-benzhydryl α-arylaminonitrile intermediates were prepared in excellent yield (89-99%) and enantiomeric purity (96 to >98% ee) by enantioselective cyanation of aldimines with TMSCN/iPrOH in the presence of 2.5 mol % of an easily prepared Ti/chiral amino alcohol complex at 0 °C, without requiring slow addition of the cyanating agent. The easily racemized α-aminonitrile intermediates were efficiently hydrolyzed by an aqueous HCl/TFA mixture to give the arylglycine derivatives in good yield (60-92%) and moderate to excellent enantiomeric purity (85-98% ee).
- Banphavichit, Vorawit,Mansawat, Woraluk,Bhanthumnavin, Worawan,Vilaivan, Tirayut
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experimental part
p. 5849 - 5854
(2009/12/01)
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- An efficient synthesis of new 2-aminomethyl-1,3,4-oxadiazoles from enantiomeric phenylglycine hydrazides
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New derivatives of 2-aminomethyl-1,3,4-oxadiazole were synthesized in the reactions of N-protected phenylglycine hydrazides and triethyl orthoesters (orthoformate, orthoacetate, orthopropionate, orthobenzoate) in the presence of glacial acetic acid. Studies on the cleavage reactions of the acid-sensitive N-BOC and N-Ac 1,3,4-oxadiazoles are presented. Spectral characteristics of the compounds and attempts to elucidate the racemization phenomenon observed in products are also discussed.
- Kudelko, Agnieszka,Zieliński, Wojciech
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experimental part
p. 1200 - 1206
(2009/04/10)
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- 6-And 7-amino isoquinoline compounds and methods for making and using the same
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6- and 7-amino isoquinoline compounds are provided that influence, inhibit or reduce the action of a kinase. Pharmaceutical compositions including therapeutically effective amounts of the 6- and 7-aminoisoquinoline compounds and pharmaceutically acceptabl
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Page/Page column 11
(2009/07/25)
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- Hydrogen bond catalyzed chemoselective N-tert-butoxycarbonylation of amines
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A novel, chemoselective mono-N-Boc protection of various structurally diverse amines with di-tert-butoxypyrocarbonate (Boc)2O is described that relies on selective carbonyl activation by hydrogen bond formation. This mild, acid- and metal-free process requires only catalytic amounts of thiourea as hydrogen bond donor.
- Khaksar, Samad,Heydari, Akbar,Tajbakhsh, Mahmood,Vahdat, Seyed Mohammad
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p. 3527 - 3529
(2008/09/21)
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- 1,1,1,3,3,3-Hexafluoroisopropanol: A recyclable organocatalyst for N-Boc protection of amines
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A simple and efficient protocol for the chemoselective mono-N-Boc protection of various structurally diverse amines with di-tert-butyl dicarbonate using 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) as solvent and catalyst is described. The catalyst can be readily separated from the reaction products and recovered for direct reuse. No competitive side reactions such as formation of isocyanate, urea, and N,N-di-Boc were observed. α-Amino alcohols afforded the N-Boc derivatives without oxazolidinone formation. Georg Thieme Verlag Stuttgart.
- Heydari, Akbar,Khaksar, Samad,Tajbakhsh, Mahmood
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experimental part
p. 3126 - 3130
(2009/04/06)
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- Enantioselective aza-Henry reactions assisted by ZnII and N-methylephedrine
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(Chemical Equation Presented) Hooray aza-Henry! A combination of zinc triflate, an amine base, and (-)-N-methylephedrine (NME), which can be easily recovered and reused, leads to high enantioselectivities in the aza-Henry reaction of N-Boc-protected aldimines and nitromethane (see scheme; Boc = tert-butyloxycarbonyl).
- Palomo, Claudio,Oiarbide, Mikel,Halder, Rajkumar,Laso, Antonio,Lopez, Rosa
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p. 117 - 120
(2007/10/03)
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- Bifunctional-thiourea-catalyzed diastereo- And enantioselective Aza-Henry reaction
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Bifunctional thiourea 1a catalyzes aza-Henry reaction of nitroalkanes with N-Boc-imines to give syn-β-nitroamines with good to high diastereo- and enantioselectivity. Apart from the catalyst, the reaction requires no additional reagents such as a Lewis acid or a Lewis base. The N-protecting groups of the imines have a determining effect on the chirality of the prod ucts, that is, the reaction of N-Bocimines gives R adducts as major products, whereas the same reaction of N-phosphonoylimines furnishes the corresponding S adducts. Various types of nitroalkanes bearing aryl, alcohol, ether, and ester groups can be used as nucleophiles, providing access to a wide range of useful chiral building blocks in good yield and high enantiomeric excess. Synthetic versatility of the addition products is demonstrated by the transformation to chiral piperidine derivatives such as CP-99,994.
- Xu, Xuenong,Furukawa, Tomihiro,Okino, Tomotaka,Miyabe, Hideto,Takemoto, Yoshiji
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p. 466 - 476
(2008/09/20)
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- Electrophilic amination of enolates with oxaziridines: Effects of oxaziridine structure and reaction conditions
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A range of N-alkoxycarbonyl- and N-carboxamido-oxaziridines has been prepared to test the effects of oxaziridine structure on yields of enolate amination product. Side-products arising from reaction of aldehyde-derived oxaziridines with base were identified, while a ketone-derived oxaziridine afforded moderate yields of amination product with stabilised carbanions.
- Armstrong, Alan,Edmonds, Ian D.,Swarbrick, Martin E.,Treweeke, Nigel R.
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p. 8423 - 8442
(2007/10/03)
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- Lithium perchlorate-catalyzed Boc protection of amines and amine derivatives
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A new mild and chemoselective method for mono-N-protection of amines and amine derivatives as tert-butoxycarbonyl derivatives is reported. The reaction proceeds with lithium perchlorate (20 mol %) and pyrocarbonates, and shows general applicability. The catalytic action of LiClO4 is specific for the activation of Boc2O, thus acid-sensitive functionalities of the starting materials remain unchanged in the protection process. This procedure works well for sterically hindered primary amine as well as electron-deficient primary arylamines, primary and secondary amino alcohols, α-amino acid esters, hydroxylamines, hydrazines and sulfonamides.
- Heydari, Akbar,Hosseini, Seyed Esmaeil
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p. 1929 - 1932
(2007/10/03)
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- Indium-mediated facile cleavage of the t-butoxycarbonyl group from di-t-butylimidodicarbonate
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Di-t-butylimidodicarbonates are selectively and efficiently deprotected to the corresponding mono-BOC protected amines in high yields using indium or zinc metal in refluxing methanol. Simple BOC and CBz protected amines are unaffected by these conditions.
- Yadav,Reddy,Reddy, K.Srinivasa,Reddy, K.Bhaskar
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p. 1549 - 1551
(2007/10/03)
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- Synthesis of optically active α-arylglycines: Stereoselective Mannich-type reaction with a new chiral template
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Mannich-type reaction of phenols with iminolactone 4, readily prepared from commercially available phenylglycine, proceeded with high stereoselectivity to give α-arylglycine derivatives. The reaction was also applicable to other electron-rich aromatic compounds and aryl boronic acids. These adducts could be readily converted to the corresponding optically active α-arylglycines.
- Tohma,Endo,Kan,Fukuyama
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p. 1179 - 1181
(2007/10/03)
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- Does water suppress the racemization and decomposition of amino acids?
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Several neutral free amino acids, phenylglycine, leucine, phenylalanine and tryptophan, are heated at 100-130 °C under alkaline or acidic conditions in water or various polar organic solvents. Although serious racemization and decomposition occur in polar organic solvents such as DMF, DMSO, or ethylene glycol under alkaline conditions (K2CO3, KOH, Et3N), these phenomena do not occur, or are largely decreased, in water or water-containing organic solvents under the same alkaline conditions. Serious racemization and decomposition of free phenylglycine are also observed in AcOH, while water or aqueous AcOH (90%) largely suppress the racemization and decomposition. We discuss the possible reasons for this suppression effect of water in terms of differential solvation of bases and states of dissociation of amino acids in aqueous and organic solvents.
- Yokoyama,Hikawa,Murakami
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p. 1431 - 1434
(2007/10/03)
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- Synthesis of enantiomerically pure 2-amino alcohols from amino acids mediated by sulfoxides
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Enantiomerically pure (R1,S2)- and (S1,S2)-2-amino alcohols can be easily synthesized by stereodivergent reduction of α'-(N-Boc)amino β-keto sulfoxides (easily synthesized from readily available N-Boc amino este
- Yuste, Francisco,Ortiz, Benjamin,Carrasco, Alejandra,Peralta, Martha,Quintero, Leticia,Sanchez-Obregon, Ruben,Walls, Fernando,Garcia Ruano, Jose L.
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p. 3079 - 3090
(2007/10/03)
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- Asymmetric alkylations using SuperQuat auxiliaries - An investigation into the synthesis and stability of enolates derived from 5,5-disubstituted oxazolidin-2-ones
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Studies on the alkylation of enolates derived from a range of N-acyl-5,5-dimethyloxazolidin-2-ones and N-acyl-5,5-diphenyloxazolidin-2-ones reveal that high yields and high diastereoselectivities are best obtained when homochiral 4-isopropyl-5,5-dimethyloxazolidin-2-one is employed as a chiral auxiliary.
- Bull, Steven D.,Davies, Stephen G.,Jones, Simon,Sanganee, Hitesh J.
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p. 387 - 398
(2007/10/03)
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- Chiral electrophilic 'glycinal' equivalents. New synthons for optically active α-amino acids and 4-substituted 2-oxazolidinones
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The thermal reaction of 3-[(1S)-2-alkoxy-1-apocamphanecarbonyl]-2-oxazolones (21a-c) with dialkyl azodicarboxylates (9) results in exclusive formation of [4 + 2] type cycloadducts (22 and 23) with moderate levels of diastereofacial selection (up to 72% d.e.). The diastereomers thus obtained were readily purified and subsequent treatment with acidic methanol followed by removal of the auxiliary with LiBH4/MeOH (1:2) gave optically pure 4-methoxy-5-hydrazino-2-oxazolidinones (26 and 27), which serve as α-aminoaldehyde templates useful for the synthesis of a wide variety of optically active α-amino acids as well as 4-alkyl and 4-aryl-2-oxazolidinones.
- Matsunaga, Hirofumi,Ishizuka, Tadao,Kunieda, Takehisa
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p. 1275 - 1294
(2007/10/03)
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- SYNTHESIS OF 2-INDOLYL-1,4-BENZODIAZEPIN-5-ONES UTILIZING A MANNICH TYPE CYCLIZATION
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2-Indolyl-1,4-benzodiazepin-5-ones (3) have been efficiently synthesized from Boc-α-amino acids (4), 3-hydroxyanthranilic acid (8), and indole; the key step is a Mannich type cyclization accompanied with introduction of indole.
- Matsunaga, Nobuyuki,Harada, Hiroshi,Aoyama, Toyohiko,Shioiri, Takayuki
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p. 235 - 255
(2007/10/02)
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