- Study on the (R)-oxynitrilase activity of Pouteria sapota
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Mamey (Pouteria sapota) defatted meal was used to catalyze the enantioselective addition of HCN to α,β-unsaturated aldehydes. Using a biphasic system of diisopropyl ether and citrate buffer (0.1 M, pH 5.0, 10% v/v), the (R)-cyanohydrins obtained showed go
- Solís, Aida,Luna, Héctor,Manjarrez, Norberto,Pérez, Herminia I.
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- A Facile Synthesis of Optically Active γ-Cyanoallylic Alcohols Using Asymmetric Hydrocyanation of α,β-Alkenyl Aldehydes Followed by Stereospecific Sigmatroopic Chirality Transfer of the Cyanohydrin Acetates
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Optically active γ-cyanoallylic alcohols were synthesised by using asymmetric hydrocyanation of α,β-alkenyl aldehydes catalyzed by peptide-titanium complex to give α-cyanoallylic alcohols (cyanohydrins) with high optical yields followed by palladium compl
- Abe, Hiroshi,Nitta, Hideaki,Mori, Atsunori,Inoue, Shohei
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- Regio- and Stereospecific C- and O-Allylation of Phenols via φ-Allyl Pd Complexes Derived from Allylic Ester Carbonates
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Two complementary strategies have been developed for the C- and O-allylation of phenols via a common φ-allyl Pd complex. While O-allylation of phenols by this method is a well-recognized reaction of general utility, the associated para-selective C-allylation reaction is still in its infancy. Cationic φ-allyl Pd intermediates, derived from allylic ester carbonates and palladium(0) catalyst, were found to undergo the Friedel-Crafts-type para-selective C-allylations with nine different phenols. Both C- and O-allylated products were obtained in good to excellent yields following a metal-catalyzed regio- and stereospecific substitutive 1,3-transposition. Conditions were also identified that control access to either allylated product. Finally, a study of the equilibrium established between the two allylation products revealed that the O-allylated compound was the kinetic product and the C-allylated compound the thermodynamic product.
- Discolo, Christopher A.,Graves, Alexander G.,Deardorff, Donald R.
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- Carving the active site of almond R-HNL for increased enantioselectivity
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Structure-guided redesign of the active site of almond (R)-PaHNL5 for increased enantioselectivity resulted in four improved muteins. In particular, mutation V360I gave enhanced conversion rates and enantioselectivities higher than 96% ee for two structur
- Weis, Roland,Gaisberger, Richard,Skranc, Wolfgang,Gruber, Karl,Glieder, Anton
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- 'Gelozymes' in organic synthesis. (Part 3): Lipase mediated synthesis of enantiomerically pure (R)- and (S)-enantiomers of 2-acetoxy-4-phenyl-(E)-but-3- enenitrile
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Lipases such as Candida rugosa lipase and Pseudomonas cepacia (Amano Ps) lipase immobilized in gelatin gels (gelozymes) exhibit very high enantioselectivities (E>200) during alcoholysis of racemic 2-acetoxy-4-phenyl-(E)-but-3-enenitrile with n-butanol in hexane and diisopropyl ether. C. rugosa lipase in n-hexane shows selectivity towards the (R)-ester while P. cepacia (Amano Ps) lipase shows selectivity towards the (S)-ester producing the corresponding cyanohydrins. After decomposition of the cyanohydrin by treatment with 1M imidazole solution to cinnamaldehyde and its removal by bisulfite treatment, (R)- or (S)-enantiomer of 2-acetoxy-4-phenyl-(E) -but-3-enenitrile can be obtained in high yields (90%) and high enantiomeric excess (>99%).
- Fadnavis, Nitin W.,Radhika, Kasiraman R.,Madhuri, Kallakunta Vasantha
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- Enantioselective hydrocyanation of aldehydes catalyzed by [Li{Ru(phgly)2(binap)}]X (X = Cl, Br)
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Novel bimetallic complexes [Li{Ru[(S)-phgly]2[(S)-binap]}]X (X = Cl, Br) are readily synthesized by mixing Ru[(S)-phgly]2[(S)-binap] and LiX. A single-crystal X-ray analysis reveals the structure. These bimetallic complexes efficient
- Kurono, Nobuhito,Yoshikawa, Tatsuya,Yamasaki, Mikio,Ohkuma, Takeshi
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supporting information; experimental part
p. 1254 - 1257
(2011/05/02)
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- α-Pinene-type chiral Schiff bases as tridentate ligands in asymmetric addition reactions
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A group of tridentate Schiff bases derived from (+)-α-pinene were synthesized. The steric effects in the transition state, the importance of π-π stacking interactions as well as the electronic effects of aryl aldehydes according to Hammett constant values in the enantioselective addition of Et2Zn to aldehydes with the use of Schiff bases as chiral ligands are described. Also, a variety of aldehydes were cyanated using a catalyst prepared in situ from titanium tetraisopropoxide and chiral Schiff bases. The influence of a conjugated double-bond in the cyanation substrates on enantioselectivity was observed. The chemical structures of the chiral Schiff base-titanium alkoxide complexes are discussed based on their 1H and 13C NMR spectra. 3D models of the Zn2-complex catalyst and Ti-complex catalyst containing α-pinane-type Schiff bases based on X-ray diffraction experiments are postulated. The models presented were consistent with the reported chirality of the addition product and observed ee.
- Jaworska, Magdalena,Blocka, Ewelina,Kozakiewicz, Anna,Welniak, Miroslaw
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experimental part
p. 648 - 657
(2011/07/08)
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- Asymmetric synthesis of a new salen type-titanium complex as the catalyst for asymmetric trimethylsilylcyanation of aldehydes
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This work describes the asymmetric synthesis of a new salen-type ligand via a Diels-Alder reaction and Curtius rearrangement. The ligand with a norbornane skeleton was used in the trimethylsilylcyanation of aldehydes, but the enantioselectivity was 55%ee. The norborane skeleton was cleaved to destroy this rigidity, and the eanatioselectivity was thereby increased to 85%ee.
- Lin, Zheng-Chang,Chen, Chinpiao
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experimental part
p. 726 - 737
(2011/04/23)
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- [Ru(phgly)2(binap)]/Li2CO3: A Highly Active, Robust, and Enantioselective Catalyst for the Cyanosilylation of Aldehydes
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The right combination: A series of aromatic, heteroaromatic, aliphatic, and α,β-unsaturated aldehydes can be converted into the desired silylated cyanohydrins by reaction with (CH3)3SiCN and a catalyst system consisting of the combination of a chiral ruthenium complex and Li2CO3 (see scheme). The reaction is highly enantioselective and affords the R products with up to 98% ee within 24 h at a substrate-tocatalyst ratio of 10000:1. (Chemical Equation Presented).
- Kurono, Nobuhito,Arai, Kenta,Uemura, Masato,Ohkuma, Takeshi
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supporting information; experimental part
p. 6643 - 6646
(2009/03/12)
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- A novel chiral (salen)AlIII complex catalyzed asymmetric cyanosilylation of aldehydes
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A novel chiral (salen)AlIII complex was synthesized through the reaction of Et2AlCl and salen (R,R)-1 derived from (R,R)-11,12-diamino-9,10-dihydro-9,10-ethanoanthracene. This complex is an efficient catalyst for the asymmetric trimethylsilylcyanation of aldehydes in the presence of tributylphosphane oxide as an additive. The use of 1 mol-% of the complex led to the corresponding cyanohydrins in high yields (85-94%) with good-to-excellent enantioselectivities (42-92%ee). Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Zeng, Zebing,Zhao, Guofeng,Zhou, Zhenghong,Tang, Chuchi
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experimental part
p. 1615 - 1618
(2009/04/11)
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- Synthesis of the bifunctional BINOL ligands and their applications in the asymmetric additions to carbonyl compounds
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Efficient one-step syntheses of the bifunctional BINOL and H8BINOL ligands (S)-6 and (S)-8 have been developed from the reaction of BINOL and H8BINOL with morpholinomethanol, respectively. The X-ray analyses of these compounds have revealed their structural similarity and difference. The bifunctional H8BINOL (S)-8 is found to be highly enantioselective for the reaction of diphenylzinc with many aliphatic and aromatic aldehydes and especially is the most enantioselective catalyst for linear aliphatic aldehydes. Unlike other catalysts developed for the diphenylzinc addition which often require the addition of a significant amount of diethylzinc with cooling (or heating) the reaction mixture in order to achieve high enantioselectivity, using (S)-8 needs no additive and gives excellent results at room temperature. (S)-8 in combination with diethylzinc and Ti(OiPr)4 can catalyze the highly enantioselective phenylacetylene addition to aromatic aldehydes. It can also promote the phenylacetylene addition to acetophenone at room temperature though the enantioselectivity is not very high yet. Without using Ti(OiPr)4 and a Lewis base additive, (S)-8 in combination with diethylzinc can catalyze the reaction of methyl propiolate with an aldehyde to form the highly functional γ-hydroxy-α,β-acetylenic esters except that the enantioselectivity is low at this stage. The bifunctional BINOL ligand (S)-6 in combination with Me2AlCl is found to be a highly enantioselective catalyst for the addition of TMSCN to both aromatic and aliphatic aldehydes.
- Qin, Ying-Chuan,Liu, Lan,Sabat, Michal,Pu, Lin
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p. 9335 - 9348
(2007/10/03)
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- Cross-linked aggregates of the hydroxynitrile lyase from Manihot esculenta: Highly active and robust biocatalysts
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The precipitation and cross-linking into CLEAs of the hydroxynitrile lyase (E.G. 4.1.2.10) from Manihot esculenta was investigated and an optimized procedure, which involved precipitation with (NH4)2SO 4, was developed. It
- Chmura, Andrzej,Van Der Kraan, Geert M.,Kielar, Filip,Van Langen, Luuk M.,Van Rantwijk, Fred,Sheldon, Roger A.
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p. 1655 - 1661
(2007/10/03)
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- Cross-linked aggregates of (R)-oxynitrilase: A stable, recyclable biocatalyst for enantioselective hydrocyanation
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(Chemical Equation Presented) The (R)-oxynitrilase from almonds was immobilized as a cross-linked enzyme aggregate (CLEA) via precipitation with 1,2-dimethoxyethane and subsequent cross-linking using glutaraldehyde. The resulting preparation was a highly
- Van Langen, Luuk M.,Selassa, Rhoderick P.,Van Rantwijk, Fred,Sheldon, Roger A.
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p. 327 - 329
(2007/10/03)
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- The substrate spectrum of mandelate racemase: Minimum structural requirements for substrates and substrate model
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Mandelate racemase (EC 5.1.2.2) is one of the few biochemically well-characterized racemases. The remarkable stability of this cofactor-independent enzyme and its broad substrate tolerance make it an ideal candidate for the racemization of non-natural α-hydroxycarboxylic acids under physiological reaction conditions to be applied in deracemization protocols in connection with a kinetic resolution step. This review summarizes all aspects of mandelate racemase relevant for the application of this enzyme in preparative-scale biotransformations with special emphasis on its substrate tolerance. Collection and evaluation of substrate structure-activity data led to a set of general guidelines, which were used as basis for the construction of a general substrate model, which allows a quick estimation of the expected activity for a given substrate.
- Felfer, Ulfried,Goriup, Marian,Koegl, Marion F.,Wagner, Ulrike,Larissegger-Schnell, Barbara,Faber, Kurt,Kroutil, Wolfgang
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p. 951 - 961
(2007/10/03)
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- Asymmetric cyanohydrin synthesis catalyzed by Al(salen)/triphenylphosphane oxide
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Various aldehydes undergo asymmetric trimethylsilylcyanation with (CH 3)3SiCN (TMSCN) in the presence of a chiral Al(salen) complex and Ph3PO as the catalyst. This is a double activation where Al(salen) plays the role of Lewis acd and POPh3 acts as a Lewis base. Various kind of aldehydes were subjected to the enantioselective addition of (CH3)3SiCN at temperatures between -40 °C and -50 °C. Hydrolysis of the adducts gave cyanohydrins with over 90 % yield and 80 % ee in most cases. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Kim, Sung Soo,Song, Dae Ho
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p. 1777 - 1780
(2007/10/03)
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- Highly enantioselective cyanosilylation of aldehydes catalyzed by novel β-amino alcohol-titanium complexes
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The β-amino alcohol 1b-Ti(Oi-Pr)4 complex has been shown to catalyze the enantioselective cyanosilylation of aldehydes efficiently. In the presence of 5 mol % of 1b-Ti(Oi-Pr)4 complex catalyst, the aromatic, conjugated, heteroaromatic, and aliphatic aldehydes were converted to their corresponding trimethylsilyl ethers of cyanohydrins in 90-99% yields with up to 94% ee under mild conditions.
- Li, Yan,He, Bin,Qin, Bo,Feng, Xiaoming,Zhang, Guolin
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p. 7910 - 7913
(2007/10/03)
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- Enantioselective addition of trimethylsilyl cyanide to aldehydes catalysed by bifunctional BINOLAM-AlCl versus monofunctional BINOL-AlCl complexes
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A highly enantioselective cyanation of aldehydes takes place by using a bifunctional catalyst derived from 3,3′-bis(diethylaminomethyl) substituted binaphthol (BINOLAM) and dimethylaluminium chloride. The addition is of wide scope and runs best in toluene at temperatures ranging from -20 to -40°C, in the presence of 4 A? MS and triphenylphosphine oxide as additives. The (R)- or (S)-cyanohydrins result when using (S)- or (R)-BINOLAM-AlCl complexes, respectively. The valuable ligand can be recovered by simple extractive work-up and recycled without loss of efficiency (both in terms of chemical and stereochemical yields). This methodology is applied to the Shibasaki synthesis of epothilone A. All the evidence available for the BINOLAM-AlCl enantioselective addition of TMSCN to aldehydes call for the intervention of a hydrocyanation reaction, addition of a catalytic amount of hydrogen cyanide, generated in situ, to an aldehyde, followed by O-silylation. In order to determine the role of the basic amino groups of BINOLAM, comparative studies are carried out with the monofunctional 1,1′-binaphthol-derived complex BINOL-AlCl. Graphical Abstract.
- Casas, Jesús,Nájera, Carmen,Sansano, José M.,Saá, José M.
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p. 10487 - 10496
(2007/10/03)
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- Evaluation of guanabana (Annona muricata) seed meal as a source of (S)-oxynitrilase
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Guanabana seed meal is a source of (S)-oxynitrilase which biocatalyzes the enantioselective addition of HCN to aromatic, heteroaromatic and α,β-unsaturated aldehydes to produce cyanohydrins.
- Solis, Aida,Luna, Hector,Perez, Herminia I.,Manjarrez, Norberto
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p. 2351 - 2353
(2007/10/03)
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- Design of a new bifunctional asymmetric catalyst from carbohydrates: Application to catalytic asymmetric cyanosilylation of aldehydes and acetophenone
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A new active Lewis acid-Lewis base bifunctional asymmetric catalyst 7 was developed using carbohydrate as a scaffold and this catalyst was applied to the asymmetric cyanosilylation of aldehydes and acetophenone. The β-Ph group at the 6-position of 7 was found to be important for a high asymmetric induction (up to 80% ee) by bringing the Al and the phosphine oxide at optimum positions for a dual activation of carbonyl compounds and TMSCN. (C) 2000 Elsevier Science Ltd.
- Kanai, Motomu,Hamashima, Yoshitaka,Shibasaki, Masakatsu
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p. 2405 - 2409
(2007/10/03)
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- Development of a family of β-amino alcohol ligands with two stereocenters for highly efficient enantioselective trimethylsilylcyanation of aldehydes
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The asymmetric addition of Me3SiCN to aldehydes catalyzed by titanium(IV) complexes of N-sulfonylated derivatives of β-amino alcohols gave excellent ee's up to 96% ee.
- You,Gau,Choi
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p. 1963 - 1964
(2007/10/03)
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- Enzymatic Synthesis of (R)-Cyanohydrins by Three (R)-Oxynitrilase Sources in Micro-aqueous Organic Medium
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The enantioselective synthesis of optically active (R)-cyanohydrins generated from several aromatic, heteroaromatic and aliphatic aldehydes and methyl ketones was carried out using almond, peach or loquat meal as (R)-oxynitrilase sources in diisopropylether under micro-aqueous conditions The micro-aqueous reaction system, which is superior to the conventionally used water-organic biphase reaction system, performed well over the temperature range of 4 deg C to 30 deg C.
- Lin, Guoqiang,Han, Shiqing,Li, Zuyi
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p. 3531 - 3540
(2007/10/03)
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- Synthesis of (R)- and (S)-2-hydroxy-3-enoic acid esters
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The synthesis of (R)- and (S)-2-hydroxy-3-enoic acid esters [(R)-1a-d and (S)-1a-c] is described. The (R) enantiomers were prepared by a Pinner synthesis from the corresponding (R)-cyanohydrins [(R)-2a-d], which in turn were obtained by R-oxynitrilase- (E.C. 4.1.2.10)-catalyzed addition of HCN to the α,β-unsaturated aldehydes 3a-d. For the preparation of the (5) enantiomers an inversion of the configuration had to be implemented. A critical evaluation of the two possible sequences: inversion of the configuration of the cyanohydrins followed by solvolysis of the nitrile function, and solvolysis of the cyanohydrins followed by inversion of the configuration of the resulting α-hydroxy esters, came out in favor of the latter pathway.
- Warmerdam,Van Den Nieuwendijk,Kruse,Brussee,Van Der Gen
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- Preparation of optically active cyanohydrins using the (S)-hydroxynitrile lyase from Hevea brasiliensis
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Several aliphatic, aromatic and heteroaromatic aldehydes have been converted into the chiral cyanohydrins using the (S) hydroxynitrile lyase from Hevea brasiliensis. The corresponding cyanohydrins were obtained in moderate to good yield and high enantiomeric excess with the exeption of phenyloxyacetaldehyde, benzyloxyacetaldehyde and the pyrrole-, pyridine- and indolealdehydes investigated. In contrast to previously reported results, cinnamaldehyde could be converted into (S)-(-)-2-hydroxy-4-phenyl-(E)-but-3- enenitrile with good selectivity by means of optimized reaction conditions.
- Schmidt, Michael,Herve, Stephanie,Klempier, Norbert,Griengl, Herfried
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p. 7833 - 7840
(2007/10/03)
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- Sulfoximine-titanium reagents in enantioselective trimethylsilylcyanations of aldehydes
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Chiral titanium reagents derived from optically active sulfoximines and Ti(O-i-Pr)4 promote the asymmetric addition of trimethysilyl cyanide to aldehydes affording cyanohydrins in high yields with good enantioselectivities (up to 91% ee). The ligand structure and the reaction conditions have been optimized. With substoichiometric amounts of the sulfoximine-titanium reagent the product is obtained in decreased yield with lower enantiomeric excess. The molecular structures of (R)-S-(2-hydroxypheny)-S-methyl sulfoximine [(R)-4a] and (R)-S-(2-hydroxyphenyl)-S-(1.1-dimethylethyl) sulioximine [(R)-4d) have been determined by X-ray diffraction analysis. Acta Chemica Scandinavica 1996.
- Bolm, Garsten,Mueller, Peter,Harms, Klaus
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p. 305 - 315
(2007/10/03)
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- Enantioselective trimethylsilylcyanation of aldehydes
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A chiral titanium reagent derived from optically active sulfoximine (R)-3 and Ti(O-i-Pr)4 promotes the asymmetric addition of trimethylsilylcyanide to aldehydes affording cyanohydrins in high yields with good enantioselectivities (up to 91% ee).
- Bolm, Carsten,Mueller, Peter
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p. 1625 - 1628
(2007/10/02)
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- Asymmetric Carbon-Carbon Bond Forming Reactions Catalyzed by Chiral Schiff Base-Titanium Alkoxide Complexes
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The enantioselective addition of trimethylsilyl cyanide to a variety of aldehydes proceeded by the aid of a catalyst prepared in situ from titanium tetraisopropoxide and chiral Schiff bases and gave the corresponding cyanohydrins in high optical yield (up to 96percent e.e.).A remarkable rate enhancement was brought about by the addition of the Schiff base to the titanium alkoxide mediated silylcyanation of aldehydes.This catalyst system also promoted the highly enantioselective reaction of diketene with aldehydes, which led to the formation of optically active 5-hydroxy-3-oxoesters.
- Hayashi, Masahiko,Inoue, Tetsuya,Miyamoto, Yasunori,Oguni, Nobuki
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p. 4385 - 4398
(2007/10/02)
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- Enantioselective Trimethylsilylcyanation of Some Aldehydes Catalyzed by Chiral Schiff Base-Titanium Alkoxide Complexes
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A variety of aldehydes (aromatic, heteroaromatic, α,β-unsaturated, and nonconjugate aliphatic aldehydes) has been trimethylsilylcyanated in highly enantiomeric excess (ee) with a catalyst prepared in situ from titanium tetraisopropoxide and chiral Schiff bases.A remarkable rate enhancement was brought about by the addition of the Schiff base into the titanium alkoxide mediated silylcyanation of aldehydes.The chemical structure of chiral Schiff base-titanium alkoxide complexes is discussed based on their 13C NMR spectra, field desorption (FD) mass spectra, and molecular weights.
- Hayashi, Masahiko,Miyamoto, Yasunori,Inoue, Tetsuya,Oguni, Nobuki
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p. 1515 - 1522
(2007/10/02)
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- Peptide-titanium complex as catalyst for asymmetric addition of hydrogen cyanide to aldehyde
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The complex of titanium ethoxide and an acyclic dipeptide ester whose terminal amino group is modified to a salicylal-type Schiff base catalyzes the asymmetric addition of hydrogen cyanide to aldehydes with high enantioselectivity. In the reaction of benzaldehyde and hydrogen cyanide, (R)-mandelonitrile is obtained with an enantiomeric excess of 90% when N-((2-hydroxy-1-naphthyl)methylene)-(S)-valyl-(S)-tryptophan methyl ester is employed. In place of the dipeptide, the amide derivatives of an amino acid modified by substituted salicylaldehyde, such as N-(3,5-dibromosalicylidene)-(S)-valine piperidide, exhibit an entirely opposite stereoselectivity to yield S-cyanohydrins with optical purities up to 97% ee. This novel peptide-titanium complex, therefore, enables us to afford optically active cyanohydrins of both absolute configurations by using natural S-amino acids as chiral auxiliaries.
- Nitta, Hideaki,Yu, Donghai,Kudo, Masanobu,Mori, Atsunori,Inoue, Shohei
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p. 7969 - 7975
(2007/10/02)
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- Asymmetric Addition of Hydrogen Cyanide to Substituted Benzaldehydes Catalyzed by a Synthetic Cyclic Peptide, Cyclo((S)-phenylalanyl-(S)-histidyl)
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Using cyclo((S)-phenylalanyl-(S)-histidyl) as catalyst, optically active cyanohydrins from substituted benzaldehydes with p-methyl, m-methyl, o-methyl, m-methoxyl, or m-phenoxyl group were obtained with optical yield of 82-33percent.For the asymmetric cyanohydrin synthesis, nonpolar solvent such as benzene or carbon tetrachloride was advantageous, while on asymmetric synthesis took place in methanol or dimethyl sulfoxide.
- Kobayashi, Yoshiyuki,Asada, Shoichi,Watanabe, Ichigen,Hayashi, Hiroaki,Motoo, Yoshiyuki,Inoue, Shohei
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p. 893 - 896
(2007/10/02)
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