- 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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- 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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- Improved practical asymmetric synthesis of α-alkylmandelic acids utilizing highly diastereoselective alkylation of 5-aryl-2-(1-naphthyl)-1,3- dioxolan-4-ones
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A practical method for the synthesis of optically pure α- alkylmandelic acids 1 is described. The present improved robust method involved two reactions: a mild, convenient, stereo-selective preparation of chiral cis-5-aryl-2-(1-naphthyl)-1,3-dioxolan-4-ones, 9a-c, and highly diastereoselective alkylation of 9a-c, followed by the hydrolysis.
- Misaki, Tomonori,Ureshino, Satoko,Nagase, Ryohei,Oguni, Yumiko,Tanabe, Yoo
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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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- 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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- 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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- Me2Zn-Mediated Catalytic Enantio- and Diastereoselective Addition of TosMIC to Ketones
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The first catalytic asymmetric addition of TosMIC to unactivated ketones is presented. A combination of Me2Zn and aminoalcohol catalyst promoted the aldol addition/cyclization reaction to render oxazolines possessing a fully substituted stereocenter with excellent yields (up to 92 %), high enantioselectivities (up to 96 %), and complete diastereoselectivity. The chiral oxazolines were then used to give, after a straightforward acid hydrolysis, enantioenriched building blocks bearing tertiary alcohol motifs such as hydroxylaldehydes, hydroxylacids, and hydroxylesters without racemization.
- Keeri, Abdul Raheem,Gualandi, Andrea,Mazzanti, Andrea,Lewinski, Janusz,Cozzi, Pier Giorgio
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supporting information
p. 18949 - 18952
(2016/01/26)
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- An efficient synthetic approach towards fully functionalized tetronic acids: The use of 1,3-dioxolane-2,4-diones as novel protected-activated synthons of α-hydroxy acids
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A new strategy for the synthesis of tetronic acids with control over the regioselective introduction of substituents at the C-5 position has been developed. The construction of the densely functionalized quaternary carbon center within these molecules is of great importance. The key element for the proposed protocol was the utilization of O-carboxyanhydrides (OCA's) of optically active α-hydroxy acids, as promising bidentate protective/activating precursors. The structure of the new compounds was investigated by using NMR spectral data and X-ray structural analyses.
- Prousis, Kyriakos C.,Markopoulos, John,Mckee, Vickie,Igglessi-Markopoulou, Olga
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p. 8637 - 8648
(2015/10/19)
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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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- 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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- 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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- Investigation of the Diastereoselectivity in the Addition of Organometallics to the α-Keto Esters of Axially Chiral 1,1'-Binaphthalen-2-ol Derivatives
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The inherent chiral induction abilities of axially chiral 2'-substituted 1,1'-binaphthalen-2-ols 2a-f as the chiral auxiliary for the addition of organometallics to their α-keto acid esters were examined as a function of the following reaction variables: size of the 2'-substituent, nature of the organometallic reagent, solvent, and temperature.In the addition of MeMgI to the phenylglyoxylates 3a-f of the alcohols 2a-f, the corresponding atrolactic acid esters 5a-f and 6a-f were obtained with up to 52percent diastereoisomeric excess (d.e.).The preferred diastereoisomer depended on the size of the 2'-substituent, and thus could not solely be determined by the helicity of the 1,1'-binaphthalene framework.By using MeZnI as the nucleophile, the selectivity increased up to 84percent d.e. with the same diastereofacial selectivity as that of MeMgI.On the other hand, the diastereofacial selection was reversed when MeTiCl3 was employed as the nucleophile, with low selectivity (14percent d.e.).It is concluded that MeMgI or MeZnI, as a nucleophile of low Lewis acidity, adds to the keto ester moiety in the s-trans conformation, while the strong Lewis acid MeTiCl3 mainly adds to the s-cis conformer from the same direction as that of the Grignard addition, thus giving the opposite diastereoisomer.
- Tamai, Yasufumi,Nakano, Tomoyuki,Miyano, Sotaro
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p. 439 - 446
(2007/10/02)
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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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- 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 SYNTHESES OF α-HYDROXYACIDS USING N-BENZYL-4,4,7α-TRIMETHYL-TRANS-OCTAHYDRO-1,3-BENZOXAZINE AS A CHIRAL ADJUVANT
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Addition of Grignard and organolithium reagents to as well as hydride reduction of 2α-benzoyl-N-benzyl-4,4,7α-trimethyl-trans-octahydro-1,3-benzoxazine (2, Y = C6H5CO) and addition of phenylmagnesium bromide to the corresponding 2-acetyl analog (11) proceed in highly diastereoselective fashion to produce virrtually exclusively the diastereomer predicted on the basis of Cram's chelate rule if chelation involves the ring oxygen atom.Mild acid hydrolysis of the adducts followed by selective oxidation produces highly enantiomerically pure α-hydroxyacids with clean recovery of the chiral adjuvant.
- He, Xu-Chang,Eliel, Ernest L.
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p. 4979 - 4988
(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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- Asymmetric Syntheses Based on 1,3-Oxathianes. 2. Synthesis of Chiral Tertiary α-Hydroxy Aldehydes, α-Hydroxy Acids, Glycols (RR'C(OH)CH2OH), and Carbinols (RR'C(OH)CH3) in High Enantiomeric Purity
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A chiral 1,3-oxathiane (5) prepared from (+)-pulegone in three steps is converted to diastereomerically pure equatorial 2-acyl derivatives by lithiation, condensation with aldehydes, and Me2SO oxidation.Reaction of the resulting ketones with Grignard reagents at -78 deg C again proceeds highly stereoselectively (diastereomer excess generally above 90percent) according to Cram's rule (cyclic model).The resulting tertiary carbinols when cleaved with NCS/AgNO3 give chiral tertiary α-hydroxy aldehydes, RR'C(OH)CHO, plus a mixture of epimeric sultines which may be readily reconverted to the starting oxathiane.The hydroxy aldehydes have been oxidized to chiral tertiary α-hydroxy acids, RR'C(OH)CO2H, and reduced to primary-tertiary glycols, RR'C(OH)CH2OH, and further to tertiary carbinols, RR'C(OH)CH3, all with over 90percent ee.The opposite enantiomers of these compounds (again >90percent ee) may be obtained by starting with a diastereomeric 1,3-oxathiane (6), also available from (+)-pulegone.The configurations of the chiral products may be deduced from the manner of preparation and the assumption that Cram's rule is valid and agree with prior assignments in the literature.
- Lynch, Joseph E.,Eliel, Ernest L.
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p. 2943 - 2948
(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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- 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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