- Highly Diastereoselective Addition of Organometallics to Novel Chiral α-Ketoamides of (S)-2-Methoxymethylindoline
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The stereocontrolled nucleophilic addition of organometallics to novel chiral α-ketoamides which were synthesized from (S)-2-methoxymethylindoline as a chiral auxiliary was carried out to obtain α-hydroxyamides with extremely high diastereoselectivities (up to dr 99:1).
- Kim, Yong Hae,Byun, Il Suk,Choi, Jun Young
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- La1?xSrxFeO3 perovskite electrocatalysts for asymmetric electrocarboxylation of acetophenone with CO2
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The use of La1?xSrxFeO3 (x= 0, 0.1, 0.2, 0.3, 0.4 and 0.5) cathodes in asymmetric electrocarboxylation of acetophenone with CO2 induced by chiral auxiliary CoII-(salen) was investigated for the first time. Optically active 2-hydroxy-2-phenylpropionic acid with 94% enantiomeric excess and 68% yield were obtained. The superior asymmetric electrocarboxylation performance may derive from the Fe4+ species and the increased lattice oxygen concentration on the surface of La0.7Sr0.3FeO3 (LSF-0.3) induced by Sr-doping, together with an accelerated electron transfer and an increased electrochemically active surface area. Here, perovskite oxide catalyst has an acid function, which is supplied by Fe4+ ions, can participate in the reaction by coordinating with acetophenone. Moreover, the LSF-0.3 has considerable stability and reusability. By cyclic voltammograms and contrast experiments, a mechanism was proposed for the asymmetric electrocarboxylation reaction.
- Yang, Li-Rong,Zhang, Jing-Jie,Zhao, Yi-Jun,Wang, Zhuo-Lin,Wang, Huan,Lu, Jia-Xing
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- Solvent-induced chirality switching in the enantioseparation of regioisomeric hydroxyphenylpropionic acids via diastereomeric salt formation with (1R,2S)-2-amino-1,2-diphenylethanol
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The enantioseparation of three hydroxyphenylpropionic acid isomers via diastereomeric salt formation with (1R,2S)-2-amino-1,2-diphenylethanol has been demonstrated. The racemates of all three acid isomers were successfully separated with high efficiency (0.56–0.84) after single crystallization. For 2-hydroxy-3-phenylpropionic acid 4, the configuration of the less-soluble salt was controlled by the crystallization solvent: the (R)-4 salt was crystallized from water, while 2-propanol afforded the (S)-4 salt. The chiral recognition mechanism of the three acids was discussed based on the crystal structures of the diastereomeric salts.
- Kodama, Koichi,Nagata, Jun,Kurozumi, Nobuhiro,Shitara, Hiroaki,Hirose, Takuji
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supporting information
p. 460 - 466
(2017/03/23)
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- Entrapment of a chiral cobalt complex within silver: A novel heterogeneous catalyst for asymmetric carboxylation of benzyl bromides with CO2
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A novel way to accommodate heterogeneous catalysis, CO2 fixation and asymmetric synthesis on one catalyst is reported. The [Co]@Ag composite was prepared for the first time and used for asymmetric carboxylation of benzyl bromides with CO2. All the procedures were performed under mild conditions. Moreover, the [Co]@Ag composite has terrific stability and reusability.
- Yang, Heng-Pan,Yue, Ying-Na,Sun, Qi-Long,Feng, Qiu,Wang, Huan,Lu, Jia-Xing
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supporting information
p. 12216 - 12219
(2015/07/27)
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- Development of a new family of chiral auxiliaries
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A new family of chiral auxiliaries designed on a conformationally restricted version of (-)-8-phenylmenthol has been developed. Both enantiomers are available from an inexpensive synthesis conducted on multigram scale. A first application has showed compa
- Gelat, Fabien,Richard, Vincent,Berger, Olivier,Montchamp, Jean-Luc
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p. 1819 - 1821
(2015/04/27)
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- Absolute configuration and enantiomeric composition of partially resolved mandelic,atrolactic and lactic acids by 1H NMR of their (S)-2-methylbutyl esters
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The mandelic,atrolactic and lactic acid esters of the (S)-2-methyl-1- butanol were examined as diastereomeric derivatives for the stereochemical analysis of the mentioned acids by 1H nuclear magnetic resonance (NMR) at 300 MHz. The diastereomer
- Da C. Andrade, Francisco A.,De L. Mendes, Maricleide P.,Da Fonseca, Neuracy C.
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p. 1006 - 1011
(2013/08/23)
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- Evaluation of dalbavancin as chiral selector for HPLC and comparison with teicoplanin-based chiral stationary phases
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Dalbavancin is a new compound of the macrocyclic glycopeptide family. It was covalently linked to 5 lm silica particles using two different binding chemistries. Approximately 250 racemates including (a) heterocyclic compounds, (b) chiral acids, (c) chiral amines, (d) chiral alcohols, (e) chiral sulfoxides and sulfilimines, (f) amino acids and amino acid derivatives, and (g) other chiral compounds were tested on the two new chiral stationary phases (CSPs) using three different mobile phases. As dalbavancin is structurally related to teicoplanin, the same set of chiral compounds was screened on two commercially available teicoplanin CSPs for comparison. The dalbavancin CSPs were able to separate some enantiomers that were not separated by the teicoplanin CSPs and also showed improved separations for many racemates. However, there were other compounds only separated or better separated on teicoplanin CSPs. Therefore, the dalbavancin CSPs are complementary to the teicoplanin CSPs.
- Zhang, Xiaotong,Bao, Ye,Huang, Ke,Barnett-Rundlett, Kimber L.,Armstrong, Daniel W.
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experimental part
p. 495 - 513
(2010/08/20)
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- B-allenyl- and B-(γ-trimethylsilylpropargyl)-10-phenyl-9- borabicyclo[3.3.2]decanes: Asymmetric synthesis of propargyl and α-allenyl 3°-carbinols from ketones
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Simple and efficient Grignard procedures are reported for the syntheses of B-allenyl-10-(phenyl)-9-borabicyclo[3.3.2]decane (1) and its B-(γ-trimethylsilylpropargyl) counterpart (2) in both enantiomeric forms. Both add selectively to ketones, providing propargyl- and α-silylallenyl 3°-carbinols, respectively (i.e., 6 (61-93% ee) and 9 (64-98% ee)). The air-stable boron byproduct is efficiently recovered and recycled back to either 1 or 2. The ozonolysis and bromination of 9 provide nonracemic α-hydroxy acids and γ-bromopropynyl carbinols, respectively.
- Hernandez, Eliud,Burgos, Carlos H.,Alicea, Eyleen,Soderquist, John A.
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p. 4089 - 4091
(2007/10/03)
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- Enantioselective synthesis of either enantiomer of α-alkyl-α- hydroxy-α-phenylacetic acids using chiral auxiliaries
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The enantioselective synthesis of either enantiomer of α-alkyl- α-hydroxy-α-phenylacetic acids was achieved by using 2-acyloxathianes 1a-c and the mixed acyl-S,O-acetals 7 and 8 as chiral auxiliaries, which can straightforwardly be prepared from (1R)-(-)-myrtenal. This procedure allowed the preparation of the title compounds in >95% enantiomeric excess (ee).
- Perez-Estrada, Salvador,Lagunas-Rivera, Selene,Vargas-Diaz, Maria Elena,Velazquez-Ponce, Pedro,Joseph-Nathan, Pedro,Zepeda, L. Gerardo
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p. 1837 - 1843
(2007/10/03)
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- Stereoselective synthesis of α-alkyl-α-hydroxylphenylacetic acid. Part (I): Asymmetric alkylation of (S)-mandelic acid
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An effective asymmetric synthesis of α-alkyl-α-hydroxyl phenyl acetic acid using benzaldehyde as steric hindrance agent has been accomplished by utilising the readily available and inexpensive chiral starting material, (S)-mandelic acid. The ee was determined by 1H NMR with Eu(hfc) 3 as shift reagent.
- Han, Xiang-Yu,Liu, He,Liu, Chun-He,Wu, Bo,Zhong, Bo-Hua,Liu, Ke-Liang
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p. 816 - 817
(2007/10/03)
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- New S,O-acetals from (1R)-(-)-myrtenal as chiral auxiliaries in nucleophilic additions
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Treatment of hydroxythiol 4 with α,α-diethoxyacetophenone at room temperature yielded a mixture of epimeric S,O-acetals 6 and 7 (1:4, 92% yield), which were efficiently separated by flash chromatography. The OTBS derivatives 8 and 9 were treated with several Grignard reagents to afford carbinols 10 and 13 respectively (85-99% yield, >95% dr). After successive hydrolysis and reduction of 10 and 13 it is possible to obtain either enantiomer of diols 16 in high optical purity (>95% er).
- Chacón-García, Luis,Lagunas-Rivera, Selene,Pérez-Estrada, Salvador,Vargas-Díaz, M. Elena,Joseph-Nathan, Pedro,Tamariz, Joaquín,Zepeda, L. Gerardo
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p. 2141 - 2145
(2007/10/03)
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- 7-Mesityl-2,2-dimethylindan-1-ol: A novel alcohol which serves as both a chiral auxiliary and a protective group for carboxy functions
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A novel chiral indanol 11 is conveniently synthesized by using a stepwise displacement of the methoxy groups of 2,6-dimethoxybenzoic ester 1 by a vinyl and then an aryl Grignard reagent as the key step. The racemic indanol 11 is optically resolved as the diastereomeric (Sa)-2′-methoxy-1,1′-binaphthyl-2-carboxylic esters 12 by column chromatography. The absolute stereochemistry of the indanol (+)-11 is established to be S by an X-ray crystallographic analysis of the ester (Sa,S)-12. Performance of the indanol 11 as a chiral auxiliary, and as a protective group for the carboxy function, is examined in the atrolactic acid synthesis from phenylglyoxylic ester 13 and methylmagnesium iodide and in the biphenyl coupling reaction of 2,3-dimethoxybenzoic ester 15 with 2-methoxy-4,6-dimethylphenylmagnesium bromide, resulting in quantitative formations of atrolactic ester 14 with up to 83% de and biphenyl 16 with 72% de, respectively.
- Koshiishi, Eiji,Hattori, Tetsutaro,Ichihara, Naoki,Miyano, Sotaro
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p. 377 - 383
(2007/10/03)
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- A novel enantioselective synthetic route to omuralide analogues with the potential for species selectivity in proteasome inhibition.
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[reaction in text] The building blocks shown can be combined for an enantioselective construction of the simplified omuralide analogue 4 in nine steps, with the use of (R)-atrolactic acid as a recoverable chiral controller.
- Crane,Corey
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p. 1395 - 1397
(2007/10/03)
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- Grignard reactions of 4-substituted-2-keto-1,3-dioxanes: Highly diastereoselective additions controlled by a remote alkyl group
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(matrix presented) The reactions of Grignard reagents with a representative series of simple cis-2-keto-4-substituted-1,3-dioxanes have been investigated. The stereochemical outcome of these highly diastereoselective additions (dr > 90:10) is consonant wi
- Bailey, William F.,Reed, David P.,Clark, Daniel R.,Kapur, Gabriel N.
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p. 1865 - 1867
(2007/10/03)
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- Asymmetric reactions of α-ketoacid-derived hemiacetals: Stereoselective synthesis of α-hydroxy acids
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N-Acylation of prolinol with α-ketoacid chlorides results in concomitant hemiacetalization of the α-keto amide by the prolinol hydroxyl group. (R) or (S) α-hydroxy acids are obtained with good enantiomeric excess by stereodivergent reduction of these hemiacetals. Reaction with Grignard reagents at ambient temperature furnishes (R) α-alkyl mandelic acids with good stereoselectivity.
- Pansare, Sunil V.,Ravi, R. Gnana
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p. 14549 - 14564
(2007/10/03)
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- Diastereoselectivity in addition of methylmagnesium halide to benzoylformate of chiral 1,1'-binaphthalene-2,2'-diol
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The Grignard reactions of mono-benzoylformate ester of 1,1'-binaphthalene-2,2'-diol were examined to investigate the complex-induced proximity effect of the phenolic hydroxyl at C-2' under different reaction conditions. This hydroxyl group exerted a significant neighboring group participation in the reaction. The nucleophilic addition reaction proceeded with higher diastereoselectivity than that of a series of sterically similarly sized binaphthyl esters recently reported. The halogen ligand in methyl Grignard reagents plays a crucial role in controlling the degree and sense of diastereoselectivity. A plausible mechanism is also proposed.
- Fuji,Tanaka,Ahn,Mizuchi
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p. 957 - 959
(2007/10/02)
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- Chemoenzymatic Preparation of Atrolactic and Mosher's Acid using Aspergillus oryzae Protease
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Sterically demanding α-methyl- and α-trifluoromethyl-mandelic esters 5a and 6a were conveniently resolved on a large scale by a protease from Aspergillus oryzae leading to both enantiomers of atrolactic acid 5b and a precursor of Mosher's acid 6b in 75-88 percent e.e.Single recrystallisation led to optically pure material.
- Feichter, Clemens,Faber, Kurt,Griengl, Herfried
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p. 653 - 654
(2007/10/02)
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- SYNTHESE D'α-HYDROXYACIDES OPTIQUEMENT ACTIFS PAR ADDITION D'ORGANOZINCIQUES SUR LE PHENYLGLYOXALATE DE (-) MENTHYLE
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Organozinc compounds readily obtained in situ from Grignard reagents and solutions of ZnCl2 or ZnBr2 in diethylether or THF add selectively to the keto group of (-) menthyl phenylglyoxalate.A variety of α-substituted mandelic acids o
- Boireau, G.,Deberly, A.,Abenhaim, D.
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p. 5837 - 5844
(2007/10/02)
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- Direct Optical Resolution of Carboxylic Acids by Chyral HPLC on Tris(3,5-dimethylphenylcarbamate)s of Cellulose and Amylose
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A variety of racemic carboxylic acids have been for the first time directly resolved by normal-phase, high-performance liquid chromatography using a hexane-2-propanol eluting system containing a small amount (ca. 1percent) of a strong carboxylic acid, like formic acid, trichloroacetic acid, and trifluoroacetic acid.
- Okamoto, Yoshio,Aburatani, Ryo,Kaida, Yuriko,Hatada, Koichi
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p. 1125 - 1128
(2007/10/02)
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- Highly Enantioselective Claisen-Type Acylation and Dieckmann Annulation
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Enantioselective Claisen condensation reactions between various esters 1a-f and 3-acyl-4(S)-IPTT 2a,b employing lithium isopropylcyclohexylamide and HMPA gave acylated products 3a-j in 29-77percent yield and in 22-97percent ee.Asymmetric Dieckmann-type an
- Nagao, Yoshimitsu,Hagiwara, Yuichi,Tohjo, Toshiaki,Hasegawa, Yukari,Ochiai, Masahito
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p. 5983 - 5986
(2007/10/02)
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- UTILISATION DE LA SYNTHESE ATROLACTIQUE POUR L'EVALUATION DE L'EFFICACITE D'INDUCTEURS DE SYNTHESE ASYMETRIQUE.
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Atrolactic syntheses have been carried out to evaluate the potentiality, in asymmetric syntheses, of chiral inducers.The (dl)-hydroxyhelicenes 1, 2, the (dl) sec. alcohols 3-12 and the (dl)phenolic binaphtyl compound 15 have been used as inducers.The d.e. are collected in table I (6-100percent).The atrolactic asymmetric synthesis has also been carried out using three optically active inducers, namely : (-)-quinine 13, (-)-10,11-dihydroquinine 14, and R(-)-2,2,2-trifluoro-1-(9-anthryl)ethanol 6.Diastereometric and enantiomeric excesses equal or greater than 88percent have been obtained in six cases out of sixteen : (dl)-2-hydroxyheptahelicene 1 (d.e = 100percent +/-2), (1-naphtyl)-(9-anthryl)methanol 3 (d.e = 90percent) ; 2,2,2-trichloro-1-(9-anthryl)ethanol 7 (d.e = 100percent +/-2), 2,2,2-tribromo-1-(9-anthryl)ethanol 8 (d.e = 100percent +/-2), (-)-quinine 13 (e.e = 95.5percent), and (-)-2,2,2-trifluoro-1-(9-anthryl)ethanol 6 (e.e = 88percent).
- Hassine, B. Ben,Gorsane, M.,Geerts-Evrard, F.,Pecher, J.,Martin, R. H.,Castelet, D.
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p. 557 - 566
(2007/10/02)
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- SYNTHESIS OF (+)S-α-PERFLUOROETHYL-α-HYDROXYPHENYL ACETIC ACID AND HIGHLY EFFECTIVE AUXILIARIES FOR USE IN ASYMMETRIC INDUCTION
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Optically pure arene-chromium-tricarbonyl alcohols 2 and 3 (readily available in both enantiomeric forms) which are powerful inducers of chirality in Prelog-type synthesis are presented. 88percent optically pure (+)S-α-perfluoroethyl-α-hydroxyphenylacetic acid is synthesized for the first time in 3 steps and 73percent yield.
- Solladie-Cavallo, A.,Suffert, J.
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p. 1897 - 1900
(2007/10/02)
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- Optical Resolution of 2-Amino-1,2-diphenylethanol by Preferential Crystallization and Its Utilization in Fractional Crystallization and Enantioselective Reduction of Prochiral Ketones
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(-/+)-erythro-2-Amino-1,2-diphenylethanol prepared from benzoin oxime by catalytic reduction was successfully resolved into pair of optically active forms by preferential crystallization.The optically active amino alcohol was found to be useful as a basic resolving agent for optical resolution of tartaric acid, trans-2,3-oxiranedicarboxylic acid, 2-hydroxy-2-phenylpropionic acid, and 3-endo-benzamido-5-norbornene-2-endo-carboxylic acid.Chiral hydrides prepared from lithium aluminium hydride and optical active threo- and erythro-2-amino-1,2-diphenylethanol derivatives were applied to the enantioface differentiating reduction of prochiral ketones to give the corresponding optically active alcohols in the 26-72percent optical purities.
- Saigo, Kazuhiko,Ogawa, Shigeo,Kikuchi, Shigetoshi,Kasahara, Atsushi,Nohira, Hiroyuki
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p. 1568 - 1573
(2007/10/02)
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- Preferential Cryatallization of 2-Amino-2-phenylethanol and Its Application as a Resolving Agent
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(+/-)-2-Amino-2-phenylethanol (phenylglycinol) prepared from (+/-)-2-amino-2-phenylacetic acid (DL-phenylglycine) by lithium aluminium hydride reduction was efficiently resolved into a pair of optically active forms by preferential crystallization.The optically active amino alcohol was successfully applied as a basic resolving agent to the resolution of tartaric acid, 2-hydroxy-2-phenylpropionic acid, 2-hydroxy-3-phenylpropionic acid, 2-phenylpropionic acid, and 2-phenyl-2-ureidoacetic acid.
- Saigo, Kazuhiko,Miura, Hisao,Ishizaki, Kozi,Nohira, Hiroyuki
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p. 1188 - 1190
(2007/10/02)
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- SYNTHESIS OF ENANTIOMERICALLY ENRICHED ATROLACTIC ACID AND OTHER α-HYDROXY ACIDS
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The α-anions of 2-substituted 1,3-dioxolan-4-ones derived from chiral mandelic and lattic acid (2a, 2b; 3a; 10a, 10b) were alkylated with high stereoselectivity, The products formed were hydrolysed to α-hydroxy acids with 65-85percent e.e. ((S)(+)-5,7,9, (R)(-)-13).
- Frater, Gy.,Mueller, U.,Guenther, W.
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p. 4221 - 4224
(2007/10/02)
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