- The Synthesis of Chiral α-Aryl α-Hydroxy Carboxylic Acids via RuPHOX-Ru Catalyzed Asymmetric Hydrogenation
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A ruthenocenyl phosphino-oxazoline-ruthenium complex (RuPHOX?Ru) catalyzed asymmetric hydrogenation of α-aryl keto acids has been successfully developed, affording the corresponding chiral α-aryl α-hydroxy carboxylic acids in high yields and with up to 97% ee. The reaction could be performed on a gram scale with a relatively low catalyst loading (up to 5000 S/C) and the resulting products can be transformed to several chiral building blocks, biologically active compounds and chiral drugs. (Figure presented.).
- Guo, Huan,Li, Jing,Liu, Delong,Zhang, Wanbin
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p. 3665 - 3673
(2017/09/11)
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- Chemoenzymatic Preparation of Enantiomerically Enriched (R)-(–)-Mandelic Acid Derivatives: Application in the Synthesis of the Active Agent Pemoline
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The enantioselective resolution of several racemic derivatives of mandelic acid methyl ester catalyzed by lipases from Pseudomonas fluorescens (Amano AK) or Burkholderia cepacia (Amano PS-C II and Amano PS-IM) has been achieved. A gram-scale lipase-mediated kinetic resolution approach has been developed that allows the facile synthesis of the corresponding methyl (R)-(–)-mandelates with excellent enantiomeric excesses (up to >99 % ee) and reaction enantioselectivity (E values up to >200). The dopaminergic agent pemoline, used in the treatment of attention-deficit hyperactivity disorder (ADHD) and narcolepsy, was synthesized with 98 % ee in a straightforward route by condensing the prepared methyl (R)-(–)-mandelate with guanidine hydrochloride under basic conditions. The desired (R)-(+)-pemoline in optically pure form (>99 % ee) was obtained after two recrystallizations from ethanol. However, it was confirmed by chiral HPLC that optically active pemoline undergoes racemization in methanol solution.
- Potera?a, Marcin,Dranka, Maciej,Borowiecki, Pawe?
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p. 2290 - 2304
(2017/05/01)
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- Stereomodulating effect of remote groups on the NADH-mimetic reduction of alkyl aroylformates with 1,4-dihydronicotinamide-β-lactam amides
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Conformationally restricted NADH peptidomimetics 4a-e, characterized by the presence of a (1,4-dihydronicotinamide)-(β-lactam) moiety, have been synthesized and used to study the Mg2+ cation-promoted asymmetric reduction of alkyl aroylformates
- Aizpurua, Jesus M.,Palomo, Claudio,Fratila, Raluca M.,Ferrón, Pablo,Miranda, José I.
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experimental part
p. 3187 - 3194
(2010/06/12)
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- Chiral cobalt-catalyzed enantioselective aerobic oxidation of α-hydroxy esters
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A chiral cobalt-catalyzed enantioselective aerobic oxidative kinetic resolution of (±)-α-hydroxy esters, using molecular oxygen as a sole oxidant, is reported and a maximum of selectivity factor (s) 31.9 was achieved with >99% enantiomeric excess for unreacted α-hydroxy esters.
- Alamsetti, Santosh Kumar,Sekar, Govindasamy
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supporting information; experimental part
p. 7235 - 7237
(2010/12/24)
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- Convenient divergent strategy for the synthesis of TunePhos-type chiral diphosphine ligands and their applications in highly enantioselective Ru-catalyzed hydrogenations
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(Chemical Equation Presented) A convenient, divergent strategy for the synthesis of a series of modular and fine-tunable C3-TunePhos-type chiral diphosphine ligands and their applications in highly efficient Rucatalyzed asymmetric hydrogenations were explored. Up to 97 and 99% ee values were achieved for the enantioselective synthesis of β-methyl chiral amines and α-hydroxy acid derivatives, respectively.
- Sun, Xianfeng,Zhou, Le,Li, Wei,Zhang, Xumu
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p. 1143 - 1146
(2008/09/18)
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- Highly enantioselective hydrogenation of α-keto esters catalyzed by Ru-tunephos complexes
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Various enantiomerically pure α-hydroxy esters were synthesized by asymmetric hydrogenation of α-keto esters catalyzed by Ru-C n-Tunephos complex. Up to 97.1% ee has been achieved for both α-aryl and α-alkyl substituted α-keto esters. Georg Thieme Verlag Stuttgart.
- Wang, Chun-Jiang,Sun, Xianfeng,Zhang, Xumu
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p. 1169 - 1172
(2007/10/03)
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- Enantioselective homoallyl-cyclopropanation of dibenzylideneacetone by modified allylindium halide reagents-rapid access to enantioenriched 1-styryl-norcarene
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Dibenzylideneacetone (8) reacts with in situ-generated allylindium halide reagents to yield the product of a homoallyl-cyclopropanation reaction: 2-(3″-butenyl)-1,1-bis[(E)-2′-phenylethenyl]cyclopropane (9), which proceeds via step-wise cleavage of the C{double bond, long}O bond and delivery of two allyl fragments from the reagent. A range of enantiomerically enriched ligands have been tested as stoichiometric asymmetric modifiers for this process. Enantiopure compounds such as cinchona alkaloids, ephedra, aminoalcohols and tartaric acid derivatives, which have proven of utility as asymmetric modifiers for the indium-mediated allylation of aldehydes and ketones, were very inefficient in the process 8→9. However, mandelic acid derivatives, in particular mandelates, were found to be of significant potential. The absolute stereochemistry of the cyclopropane 9 has been determined by degradation to 1,1-dicarboxymethyl-2-butylcyclopropane, converging with an independent enantioselective synthesis starting from hexene. Under optimised conditions, viz. using allylindium iodide reagents and working-up with aqueous Na2SO3 to avoid iodine-mediated polymerisation, (S)-9 can be generated in 86% yield and with (S)-methyl mandelate as modifier useful enantiopurity (94/6 er) was observed. The cyclopropane product ((S)-9) undergoes RCM using standard conditions to afford a norcarene unit ((1S,6S)-1-(E)-2′-(phenylethenyl)-bicyclo[4.1.0]hept-2-ene) without loss of enantiopurity.
- Lloyd-Jones, Guy C.,Wall, Philip D.,Slaughter, Jennifer L.,Parker, Alexandra J.,Laffan, David P.
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p. 11402 - 11412
(2007/10/03)
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- Vanadium-catalyzed asymmetric oxidation of α-hydroxy esters using molecular oxygen as stoichiometric oxidant
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A vanadium-catalyzed method for the oxidative kinetic resolution of α-hydroxyesters, using oxygen as the terminal oxidant, is described. The catalyst is generated in situ from vanadium(V) tri-iso-propoxyoxide in combination with a tridentate ligand derived from 3,5-di-tert-butylsalicylaldehyde and (S)-tert-leucinol. The reaction allows for the enantioselective synthesis of both aromatic and aliphatic secondary alcohols, including those containing olefins and alkynes. Copyright
- Radosevich, Alexander T.,Musich, Christine,Toste, F. Dean
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p. 1090 - 1091
(2007/10/03)
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- Highly efficient chemo- and enantioselective enzymatic resolution of (+/-)-methyl O-acetylmandelates
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Chemo- and enantioselective enzymatic hydrolysis of (+/-)-methyl O-acetylmandelates using AmanoPS has been described with very high yields and optical purity of the products.
- Desai, Shrivallabh B.,Ganesh, Krishna N.,Argabe, Narshinha P.
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p. 918 - 920
(2007/10/03)
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- Cationic BINAP-Ru(II) Halide Complexes: Highly Efficient Catalysts for Stereoselective Asymmetric Hydrogenation of α- and β-Functionalized Ketones
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Cationic ruthenium-BINAP complexes 5, 7, and 10 of the formula Y, where X = Cl, Br, I; Y = Cl, Br, I, BF4, B(C6H5)4; arene = benzene, p-cymene, ethyl benzoate, and their enantiomers have been prepared by the reaction of arene-ruthenium halide complexes 4, 6, and 9 with (S)-BINAP or (R)-BINAP.Structures of the complexes were established by spectroscopy, conductivity, and a single-crystal X-ray analysis (5d: orthorhombic, P21212; a=20.141(2) Angstroem, b=18.504(1) Angstroem, c=12.241(1) Angstroem, V=4562.0(7) Angstroem3, Z=4, R=0.078 for unique 4177 reflections).BINAP derivatives with various substituents at the para and meta positions of four phenyl rings on phosphorus atoms and their cationic Ru(II) complexes have also been synthesized.These BINAP-Ru(II) complexes have been used as catalysts for the asymmetric hydrogenation of various unsaturated organic compounds such as α- and β-keto esters, allylic alcohols, and α,β-unsaturated carboxylic acids in excellent diastereo- and/or enantioselectivities.Catalytic activities and stereoselectivities depend highly on reaction conditions such as solvent, temperature, and additives.Variation of halogen ligands bound to ruthenium atom and substituents on four phenyl rings of BINAP also have exerted remarkable effects on the efficiency of the catalysis.Asymmetric hydrogenation of methyl (+/-)-2-(benzamidomethyl)-3-oxobutanoate catalyzed by the species derived from 9c and 3,5-(t-Bu)2-BINAP afforded the corresponding syn-(2S,3R)-17 in 98percent de and 99percent ee.
- Mashima, Kazushi,Kusano, Koh-hei,Sato, Naomasa,Matsumura, Yoh-ichi,Nozaki, Kyoko,et al.
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p. 3064 - 3076
(2007/10/02)
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- Resolution of Mandelic Acids by Lipase-catalysed Transesterifications in Organic Media: Inversion of Enantioselectivity mediated by the Acyl Donor
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The lipase-catalysed highly enantioselective deacylation and acylation of mandelic acid derivatives and the inversion of enantioselectivity mediated by the acyl donor are described.
- Miyazawa, Toshifumi,Kurita, Sota,Ueji, Shinichi,Yamada, Takashi,Kuwata, Shigeru
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p. 2253 - 2258
(2007/10/02)
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- Enantioselectivity of carbonic anhydrase catalyzed hydrolysis of mandelic methyl esters
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We report the first enantioselective hydrolysis of esters catalyzed by caebonic anhydrase.We found that mandelic methyl esters are good substrates for carbonic anhydrase.The R enantiomers are better substrates and enantiomeric excess values are moderate (40-51percent).
- Chenevert, Robert,Letourneau, Martin
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p. 314 - 316
(2007/10/02)
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