- Synthesis method of chiral trans-2-substituted naphthenic alcohol
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The invention relates to a synthesis method of chiral trans-2-substituted naphthenic alcohol. The invention provides a method for synthesizing chiral trans-cycloalkanol through asymmetric hydrogenation of palladium-catalyzed 2-substituted cyclic ketone. According to the method,a chiral diphosphine P-P * complex of metal palladium is taken as a catalyst, an acid additive is used in cooperation, asymmetric hydrogenation is carried out on a 2-substituted cyclic ketone compound to obtain a corresponding chiral trans-cycloalkanol compound. the enantiomeric excess of the chiral trans-cycloalkanol compound can reach 97% at most, and the trans-selectivity of the chiral trans-cycloalkanol compound is up to 20: 1. The method is simple and convenient to operate, practical, easy to implement, high in yield, high in atom economy and environment-friendly; the catalyst is commercially available; the reaction conditions are mild; and the method has a potential practical application value.
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Paragraph 0041-0045; 0050-0051; 0060-0061
(2021/09/08)
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- Aqueous chemoenzymatic one-pot enantioselective synthesis of tertiary α-aryl cycloketonesviaPd-catalyzed C-C formation and enzymatic C=C asymmetric hydrogenation
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An aqueous chemoenzymatic cascade reaction combining Pd-catalyzed C-C formation and enzymatic C=C asymmetric hydrogenation (AH) was developed for enantioselective synthesis of tertiary α-aryl cycloketones in good yields and excellent enantioselectivities. The stereopreference of the enzyme in AH of α-aryl cyclohexenones was studied. An enantiocomplementary enzyme was obtained by site-directed mutation.
- Luan, Pengqian,Liu, Yunting,Li, Yongxing,Chen, Ran,Huang, Chen,Gao, Jing,Hollmann, Frank,Jiang, Yanjun
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p. 1960 - 1964
(2021/03/26)
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- Palladium-catalyzed asymmetric hydrogenation of 2-aryl cyclic ketones for the synthesis oftranscycloalkanols through dynamic kinetic resolution under acidic conditions
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The first efficient palladium-catalyzed asymmetric hydrogenation of 2-aryl cyclic ketones has been described through dynamic kinetic resolution under acidic conditions, providing a facile access to chiraltranscycloalkanol derivatives with excellent enantioselectivities.
- Li, Xiang,Zhao, Zi-Biao,Chen, Mu-Wang,Wu, Bo,Wang, Han,Yu, Chang-Bin,Zhou, Yong-Gui
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supporting information
p. 5815 - 5818
(2020/06/03)
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- Preparation method of (1S, 2R)-2-phenylcyclohexanol
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The invention provides a preparation method of (1S, 2R)-2-phenylcyclohexanol. The preparation method specifically comprises the following steps: mixing and reacting a cyclohexene oxide solution, a tetrahydrofuran solution of phenyl magnesium bromide, and cuprous chloride or cuprous bromide for 1-3 h, and performing quenching treatment with an aqueous saturated ammonium chloride or saturated ammonium sulfate solution; and collecting the obtained upper organic layer, carrying out concentration, distillation and recrystallization treatment to obtain a raceme of chiral 2-phenylcyclohexanol, and carrying out resolution treatment on the raceme of chiral 2-phenylcyclohexanol to obtain (1S, 2R)-2-phenylcyclohexanol. The method allows the ee value of the obtained product to reach 98% or above, theprocess is simple, and the product purity is high.
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Paragraph 0011-0013; 0015-0018
(2020/06/02)
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- A Practical and Stereoselective In Situ NHC-Cobalt Catalytic System for Hydrogenation of Ketones and Aldehydes
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Homogeneous catalytic hydrogenation of carbonyl groups is a synthetically useful and widely applied organic transformation. Sustainable chemistry goals require replacing conventional noble transition metal catalysts for hydrogenation by earth-abundant base metals. Herein, we report how a practical in situ catalytic system generated by easily available pincer NHC precursors, CoCl2, and a base enabled efficient and high-yielding hydrogenation of a broad range of ketones and aldehydes (over 50 examples and a maximum turnover number [TON] of 2,610). This is the first example of NHC-Co-catalyzed hydrogenation of C=O bonds using flexible pincer NHC ligands consisting of a N-H substructure. Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized by fine-tuning of the steric bulk of pincer NHC ligands. Additionally, a bis(NHCs)-Co complex was successfully isolated and fully characterized, and it exhibits excellent catalytic activity that equals that of the in-situ-formed catalytic system. Catalytic hydrogenation is a powerful tool for the reduction of organic compounds in both fine and bulk chemical industries. To improve sustainability, more ecofriendly, inexpensive, and earth-abundant base metals should be employed to replace the precious metals that currently dominate the development of hydrogenation catalysts. However, the majority of the base-metal catalysts that have been reported involve expensive, complex, and often air- and moisture-sensitive phosphine ligands, impeding their widespread application. From a mixture of the stable CoCl2, imidazole salts, and a base, our newly developed catalytic system that formed easily in situ enables efficient and stereoselective hydrogenation of C=O bonds. We anticipate that this easily accessible catalytic system will create opportunities for the design of practical base-metal hydrogenation catalysts. A practical in situ catalytic system generated by a mixture of easily available pincer NHC precursors, CoCl2, and a base enabled highly efficient hydrogenation of a broad range of ketones and aldehydes (over 50 examples and up to a turnover number [TON] of 2,610). Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized in high selectivities. Moreover, the preparation of a well-defined bis(NHCs)-Co complex via this pincer NHC ligand consisting of a N-H substructure was successful, and it exhibits equally excellent catalytic activity for the hydrogenation of C=O bonds.
- Zhong, Rui,Wei, Zeyuan,Zhang, Wei,Liu, Shun,Liu, Qiang
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supporting information
p. 1552 - 1566
(2019/06/14)
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- Synthesis of Chiral Cyclic Alcohols from Chiral Epoxides by H or N Substitution with Frontside Displacement
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Diverse examples are provided of enantioselective sequences for the transformation of cycloalkenes to either chiral trans-β-substituted cycloalkanols or chiral α-amino ketones.
- Da Silva Gomes, Roberto,Reddy, Karla Mahender,Corey
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supporting information
p. 6310 - 6313
(2018/10/09)
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- (Poly)cationic λ3-Iodane-Mediated Oxidative Ring Expansion of Secondary Alcohols
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Herein, a simplified approach to the synthesis of medium-ring ethers through the electrophilic activation of secondary alcohols with (poly)cationic λ3-iodanes (N-HVIs) is reported. Excellent levels of selectivity are achieved for C–O bond migration over established α-elimination pathways, enabled by the unique reactivity of a novel 2-OMe-pyridine-ligated N-HVI. The resulting hexafluoroisopropanol (HFIP) acetals are readily derivatized with a range of nucleophiles, providing a versatile functional handle for subsequent manipulations. The utility of this methodology for late-stage natural product derivatization was also demonstrated, providing a new tool for diversity-oriented synthesis and complexity-to-diversity (CTD) efforts. Preliminary mechanistic investigations reveal a strong effect of alcohol conformation on the reactive pathway, thus providing a predictive power in the application of this approach to complex molecule synthesis.
- Walters, Jennifer C.,Tierno, Anthony F.,Dubin, Aimee H.,Wengryniuk, Sarah E.
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supporting information
p. 1460 - 1464
(2018/04/06)
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- Diastereoselective and enantioselective alkaline-hydrolysis of 2-aryl-1-cyclohexyl acetate: a CAL-B catalyzed deacylation/acylation tandem process
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Candida antarctica lipase proved to be a particularly efficient lipase for the resolution of racemic 2-arylcyclohexyl acetate in hydrolysis reaction with Na2CO3 in an organic medium. The (1R,2S)-trans-2-arylcyclohexanols 2a–2d were obtained with high ee values (up to >99%) and the selectivity reached E > 200. The influence of the enol ester and the solvent on (±)-trans-2-arylcyclohexanol in the CAL-B catalyzed acylation was also studied and compared with the deacylation. The CAL-B exhibits a better affinity for the alkaline hydrolysis reaction compared with acylation with the enol esters in the same organic solvents. The best conditions were applied to resolve a stereoisomeric mixture cis/trans-2-phenyl-1-cyclohexanol and its corresponding acetate by acylation and deacylation. The obtained results show a highly enantio- and diastereoselectivity of the CAL-B during the acylation and the deacylation in favor of the trans-(R)-enantiomer product. The resolution of a mixture of cis/trans-2-arylcyclohexanols was an easy, convenient approach to provide only one stereoisomer of a mixture of four with high enantiomeric excess.
- Belkacemi, Fatma Zahra,Merabet-Khelassi, Mounia,Aribi-Zouioueche, Louisa,Riant, Olivier
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supporting information
p. 1644 - 1650
(2017/10/12)
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- Synthetically useful variants of industrial lipases from: Burkholderia cepacia and Pseudomonas fluorescens
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Industrial enzymes lipase PS (LPS) and lipase AK (LAK), which originate from Burkholderia cepacia and Pseudomonas fluorescens, respectively, are synthetically useful biocatalysts. To strengthen their catalytic performances, we introduced two mutations into hot spots of the active sites (residues 287 and 290). The LPS-L287F/I290A double mutant showed high catalytic activity and enantioselectivity for poor substrates for which the wild-type enzyme showed very low activity. The LAK-V287F/I290A double mutant was also an excellent biocatalyst with expanded substrate scope, which was comparable to the LPS-L287F/I290A double mutant. Thermodynamic parameters were determined to address the origin of the high enantioselectivity of the double mutant. The ΔΔH? term, but not the ΔΔS? term, was predominant, which suggests that the enantioselectivity is driven by a differential energy associated with intermolecular interactions around Phe287 and Ala290. A remarkable solvent effect was observed, giving a bell-shaped profile between the E values and the log&P or ? values of solvents with the highest E value in i-Pr2O. This suggests that an organic solvent with appropriate hydrophobicity and polarity provides the double mutant with some flexibility that is essential for excellent catalytic performance.
- Yoshida, Kazunori,Ono, Masakazu,Yamamoto, Takahiro,Utsumi, Takashi,Koikeda, Satoshi,Ema, Tadashi
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supporting information
p. 8713 - 8719
(2017/11/03)
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- Directed β C-H Amination of Alcohols via Radical Relay Chaperones
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A radical-mediated strategy for β C-H amination of alcohols has been developed. This approach employs a radical relay chaperone, which serves as a traceless director that facilitates selective C-H functionalization via 1,5-hydrogen atom transfer (HAT) and enables net incorporation of ammonia at the β carbon of alcohols. The chaperones presented herein enable direct access to imidate radicals, allowing their first use for H atom abstraction. A streamlined protocol enables rapid conversion of alcohols to their β-amino analogs (via in situ conversion of alcohols to imidates, directed C-H amination, and hydrolysis to NH2). Mechanistic experiments indicate HAT is rate-limiting, whereas intramolecular amination is product- and stereo-determining.
- Wappes, Ethan A.,Nakafuku, Kohki M.,Nagib, David A.
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p. 10204 - 10207
(2017/08/10)
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- Kinetic resolution of secondary carbinols by a chiral N,N-4-dimethylaminopyridine derivative containing a 1,1′-binaphthyl unit: Hydrogen bonding affects catalytic activity and enantioselectivity
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We developed an acylative kinetic resolution of secondary carbinols using a binaphthyl-based N,N-4-dimethylaminopyridine (DMAP) derivative 1d with tert-Alcohol substituents. The reaction proceeded with a wide range of carbinols with moderate to high selectivity (s) (up to s = 79.5). Kinetic studies revealed that catalyst 1d was more catalytically active than the corresponding bis-methyl ether 1d′ or DMAP. Hydrogen bonding between tert-Alcohols of the catalyst and secondary carbinols was responsible for the enhanced reaction rate and high enantioselectivity.
- Fujii, Kazuki,Mitsudo, Koichi,Mandai, Hiroki,Suga, Seiji
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p. 1081 - 1092
(2016/10/11)
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- Highly Active Titanocene Catalysts for Epoxide Hydrosilylation: Synthesis, Theory, Kinetics, EPR Spectroscopy
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A catalytic system for titanocene-catalyzed epoxide hydrosilylation is described. It features a straightforward preparation of titanocene hydrides that leads to a reaction with low catalyst loading, high yields, and high selectivity of radical reduction. The mechanism was studied by a suite of methods, including kinetic studies, EPR spectroscopy, and computational methods. An unusual resting state leads to the observation of an inverse rate order with respect to the epoxide.
- Henriques, Dina Schwarz G.,Zimmer, Katharina,Klare, Sven,Meyer, Andreas,Rojo-Wiechel, Elena,Bauer, Mirko,Sure, Rebecca,Grimme, Stefan,Schiemann, Olav,Flowers, Robert A.,Gans?uer, Andreas
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supporting information
p. 7671 - 7675
(2016/07/07)
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- Diastereoselective and Enantioselective Silylation of 2-Arylcyclohexanols
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The silylation-based kinetic resolution of trans 2-arylcyclohexanols was accomplished by employing a triaryl silyl chloride as the derivatizing reagent with a commercially available isothiourea catalyst. The methodology is selective for the trans diastereomer over the cis, which provides an opportunity to selectively derivatize one stereoisomer out of a mixture of four. By employing this technology, a facile, convenient method to form a highly enantiomerically enriched silylated alcohol was accomplished through a one-pot reduction-silylation sequence that started with a 2-aryl-substituted ketone.
- Wang, Li,Akhani, Ravish K.,Wiskur, Sheryl L.
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supporting information
p. 2408 - 2411
(2015/05/27)
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- Enantioselective cross-coupling of meso -epoxides with aryl halides
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The first enantioselective cross-electrophile coupling of aryl bromides with meso-epoxides to form trans-β-arylcycloalkanols is presented. The reaction is catalyzed by a combination of (bpy)NiCl2 and a chiral titanocene under reducing conditions. Yields range from 57 to 99% with 78-95% enantiomeric excess. The 30 examples include a variety of functional groups (ether, ester, ketone, nitrile, ketal, trifluoromethyl, sulfonamide, sulfonate ester), both aryl and vinyl halides, and five- to seven-membered rings. The intermediacy of a carbon radical is strongly suggested by the conversion of cyclooctene monoxide to an aryl [3.3.0]bicyclooctanol.
- Zhao, Yang,Weix, Daniel J.
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supporting information
p. 3327 - 3340
(2015/03/30)
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- Highly enantioselective organocatalytic oxidative kinetic resolution of secondary alcohols using chiral alkoxyamines as precatalysts: Catalyst structure, active species, and substrate scope
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The development and characterization of enantioselective organocatalytic oxidative kinetic resolution (OKR) of racemic secondary alcohols using chiral alkoxyamines as precatalysts are described. A number of chiral alkoxyamines have been synthesized, and their structure-enantioselectivity correlation study in OKR has led us to identify a promising precatalyst, namely, 7-benzyl-3-n-butyl-4-oxa-5-azahomoadamantane, which affords various chiral aliphatic secondary alcohols (ee up to >99%, krel up to 296). In a mechanistic study, chlorine-containing oxoammonium species were identified as the active species generated in situ from the alkoxyamine precatalyst, and it was revealed that the chlorine atom is crucial for high reactivity and enantioselectivity. The present OKR is the first successful example applicable to various unactivated aliphatic secondary alcohols, including heterocyclic alcohols with high enantioselectivity, the synthetic application of which is demonstrated by the synthesis of a bioactive compound.
- Murakami, Keiichi,Sasano, Yusuke,Tomizawa, Masaki,Shibuya, Masatoshi,Kwon, Eunsang,Iwabuchi, Yoshiharu
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supporting information
p. 17591 - 17600
(2015/02/19)
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- Oxidative kinetic resolution of racemic alkyl aryl carbinols by an electronically tuned chiral nitroxyl radical
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A method for oxidative kinetic resolution of racemic alcohols catalyzed by chiral nitroxyl radical (R,R)-1 has been developed. This method is especially effective for the kinetic resolution of tert-butyl aryl carbinols (s = up to 23).
- Hamada, Shohei,Wada, Yoshiyuki,Sasamori, Takahiro,Tokitoh, Norihiro,Furura, Takumi,Kawabata, Takeo
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supporting information
p. 1943 - 1945
(2014/03/21)
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- Nickel-catalyzed regiodivergent opening of epoxides with aryl halides: Co-catalysis controls regioselectivity
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Epoxides are versatile intermediates in organic synthesis, but have rarely been employed in cross-coupling reactions. We report that bipyridine-ligated nickel can mediate the addition of functionalized aryl halides, a vinyl halide, and a vinyl triflate to epoxides under reducing conditions. For terminal epoxides, the regioselectivity of the reaction depends upon the cocatalyst employed. Iodide cocatalysis results in opening at the less hindered position via an iodohydrin intermediate. Titanocene cocatalysis results in opening at the more hindered position, presumably via TiIII-mediated radical generation. 1,2-Disubstituted epoxides are opened under both conditions to form predominantly the trans product.
- Zhao, Yang,Weix, Daniel J.
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supporting information
p. 48 - 51
(2014/01/23)
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- Kinetic resolution of secondary alcohols catalyzed by chiral phosphoric acids
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Acid instead of base: Kinetic resolution of secondary alcohols is realized using chiral Bronsted acid catalyzed acylation instead of the conventional basic conditions. A broad range of functional groups are tolerated, such as aldehydes, carboxylic acids, and enoates. The selectivity factor (s) reaches up to 215 at ambient temperature. Copyright
- Harada, Shingo,Kuwano, Satoru,Yamaoka, Yousuke,Yamada, Ken-Ichi,Takasu, Kiyosei
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supporting information
p. 10227 - 10230
(2013/10/21)
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- Synthesis of PDE IV inhibitors. First asymmetric synthesis of two of GlaxoSmithKline's highly potent Rolipram analogues
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Asymmetric syntheses of two of GlaxoSmithKline's highly potent phosphodiesterase IV inhibitors CMPI 1 and CMPO 2 have been accomplished from nitroethane and simple precursors in 8 and 7 steps, respectively. The suggested synthetic strategy involves as a key stage the silylation of enantiopure six-membered cyclic nitronates. In vitro studies of PDE IVB1 inhibition revealed a significant difference in the activity of CMPI 1 and CMPO 2 enantiomers.
- Zhmurov, Petr A.,Sukhorukov, Alexey Yu.,Chupakhin, Vladimir I.,Khomutova, Yulia V.,Ioffe, Sema L.,Tartakovsky, Vladimir A.
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p. 8082 - 8091
(2013/12/04)
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- (S)-proline-derived catalysts for the acylative kinetic resolution of alcohols: A remote structural change allows a complete selectivity switch
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A systematic preliminary study has identified a suite of catalysts, all readily prepared and derived from (S)-proline, which differ by a remote substituent only. If this substituent is capable of hydrogen-bond donation the catalyst will promote the resolu
- Gleeson, Oliver,Gun'Ko, Yurii K.,Connon, Stephen J.
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supporting information
p. 1728 - 1734
(2013/09/02)
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- A nonenzymatic kinetic resolution of (±)-trans-2-arylcyclohexanols via esterification using polymer-supported DCC, DMAP, and 3 β- acetoxyetienic acid
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A nonenzymatic kinetic resolution of (±)-trans-2-arylcyclohexanols was carried out by esterification using polymer-supported N,N′- dicyclohexylcarbodiimide (DCC), dimethylaminopyridine (DMAP), and 3β-acetoxyetienic acid. The efficiency of the kinetic resolution was comparable to the enzymatic method when arylcyclohexanols bearing a condensed-aromatic ring were used. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communication to view the free supplemental file.
- Shamoto, Kengo,Miyazaki, Atsushi,Matsukura, Mika,Kobayashi, Yuki,Shioiri, Takayuki,Matsugi, Masato
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supporting information
p. 1425 - 1431
(2013/05/22)
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- Kinetic resolution of secondary alcohols by chiral dmap derivatives prepared by the Ugi multicomponent reaction
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The kinetic resolution of secondary alcohols was examined by new chiral DMAP derivatives, which can readily be prepared by the Ugi multicomponent reaction in a one-pot operation. The initial screening of DMAP derivatives indicated that the catalyst bearing L-valine with an S configuration at the a-position of amide showed the best stereoselectivity factor. After the reaction conditions were optimized with (S,S)-4a in the kinetic resolution of secondary alcohols, various acyclic and cyclic secondary alcohols could be resolved with an s -factor of up to 12.
- Mandai, Hiroki,Irie, Shunsuke,Akehi, Masaru,Yuri, Kazunobu,Yoden, Masaaki,Mitsudo, Koichi,Suga, Seiji
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p. 329 - 340
(2013/03/28)
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- Synthesis of PDE IVb inhibitors. 3. Synthesis of (+)-, (-)-, and (±)-7-[3-(cyclopentyloxy)-4-methoxyphenyl]hexahydro-3 H -pyrrolizin-3-one via reductive domino transformations of 3-β-carbomethoxyethyl-substituted six-membered cyclic nitronates
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Simple three-step asymmetric and racemic syntheses of GlaxoSmithKline's highly potent PDE IVb inhibitor 1 were developed. The suggested approach is based on reductive domino transformations of 3-β-carbomethoxyethyl- substituted six-membered cyclic nitronates, which are easily accessed by a stereoselective [4 + 2] cycloaddition of an appropriate nitroalkene to vinyl ethers. In vitro studies of PDE IVb inhibition by enantiomeric pyrrolizidinones (+)-1 and (-)-1 were performed.
- Sukhorukov, Alexey Yu.,Boyko, Yaroslav D.,Nelyubina, Yulia V.,Gerard, Stephane,Ioffe, Sema L.,Tartakovsky, Vladimir A.
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experimental part
p. 5465 - 5469
(2012/10/07)
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- Influence of chiral thiols on the diastereoselective synthesis of γ-lactams from cyclic anhydrides
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The synthesis of γ-lactams from both four-component and imine-anhydride reactions is reported. The synthesis of 2-phenylcyclohexanethiol is described and this compound was evaluated along with an additional seven chiral thiols. A range of selectivity and yields was observed and comparisons to established reactions are made in order to account for the observed reactivity.
- Younai, Ashkaan,Fettinger, James C.,Shaw, Jared T.
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scheme or table
p. 4320 - 4327
(2012/07/28)
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- Synthesis and reactions of enantiopure substituted benzene cis-hexahydro-1,2-diols
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Enantiopure dis-dihydro-1,2-diol metabolites, obtained from toluene dioxygenase-catalysed dis-dihydroxylation of six monosubstituted benzene substrates, have been converted to their corresponding dis-hexahydro-1,2-diol derivatives by catalytic hydrogenation via their dis-tetrahydro-1,2-diol intermediates. Optimal reaction conditions for total catalytic hydrogenation of the dis-dihydro-1,2-diols have been established using six heterogeneous catalysts. The relative and absolute configurations of the resulting benzene dis-hexahydro-1,2-diol products have been unequivocally established by X-ray crystallography and NMR spectroscopy. Methods have been developed to obtain enantiopure dis-hexahydro-1,2diol diastereoisomers, to desymmetrise a meso-cishexahydro-1,2-diol and to synthesise 2-substituted cyclohexanols. The potential of these enantiopure cyclohexanols as chiral reagents was briefly evaluated through their application in the synthesis of two enantiomerically enriched phosphine oxides from the corresponding racemic phosphine precursors.
- Boyd,Sharma,Berberian,Dunne,Hardacre,Kaik,Kelly,Malone,McGregor,Stevenson
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experimental part
p. 855 - 868
(2010/07/05)
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- Effects of methyl substituents on the activity and enantioselectivity of homobenzotetramisole-based catalysts in the kinetic resolution of alcohols
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Substitution of the tetrahydropyrimidine ring in the enantioselective acyl transfer catalyst homobenzotetramisole (HBTM) 6 with methyl groups exerts a dramatic influence on its performance in the kinetic resolution of secondary alcohols. The syn-3-methyl analogue of HBTM (9a) has proved to be superior to the parent compound in terms of catalytic activity, enantioselectivity, and synthetic accessibility.
- Zhang, Yuhua,Birman, Vladimir B.
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supporting information; scheme or table
p. 2525 - 2529
(2009/12/28)
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- Gold-Catalyzed Electrophilic Addition to Arylalkynes. A Facile Method for the Regioselective Synthesis of Substituted Naphthalenes
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An interesting gold-catalyzed electrophilic addition to arylalkyne to synthesize substituted naphthalenes has been presented. Different metal hexafluoroantimonates have also been found to effect the transformation. Counter anion and oxo- and alkynophilicities of catalytic gold species might play an important role in this annulation reaction.
- Balamurugan, Rengarajan,Gudla, Vanajakshi
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supporting information; experimental part
p. 3116 - 3119
(2009/12/05)
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- Highly enantioselective organocatalytic oxidative kinetic resolution of secondary alcohols using chirally Modified AZADOs
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A highly enantioselective organocatalytic oxidative kinetic resolution (OKR) of racemic secondary alcohols has been accomplished using asymmetric organocatalysis. A panel of chirally modified 2-azaadamantane N-oxyls (AZADOs) exhibit superior catalytic act
- Tomizawa, Masaki,Shibuya, Masatoshi,Iwabuchi, Yoshiharu
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supporting information; experimental part
p. 1828 - 1831
(2009/09/06)
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- Homobenzotetramisole: An effective catalyst for kinetic resolution of aryl-cycloalkanols
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Homobenzotetramisole (HBTM), a ring-expanded analogue of the previously reported catalyst BTM, displays higher catalytic activity and a different structure-selectivity profile. It displays good enantioselectivities in kinetic resolution of secondary benzylic alcohols but is particularly effective for 2-aryl-substituted cycloalkanols.
- Birman, Vladimir B.,Li, Ximin
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supporting information; experimental part
p. 1115 - 1118
(2009/04/07)
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- Palladium-catalyzed enantioselective oxidation of chiral secondary alcohols: Access to both enantiomeric series
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(Chemical Equation Presented) Rapid resolution: A new catalyst system for the oxidative kinetic resolution of secondary alcohols leads to dramatic rate increases. This system allows the use of a diamine to provide access to either enantiomer of a range of alcohols with good selectivity factors (see scheme). This method has been applied to the formal total synthesis of (-)-amurensinine.
- Ebner, David C.,Trend, Raissa M.,Genet, Cedric,McGrath, Matthew J.,O'Brien, Peter,Stoltz, Brian M.
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scheme or table
p. 6367 - 6370
(2009/03/11)
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- Organolithium/chiral Lewis base/BF3: A versatile combination for the enantioselective desymmetrization of meso-epoxides
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BF3 can be used in combination with organolithium/strong Lewis base complexes for the enantioselective nucleophilic ring-opening or the carbenoidic rearrangement of various meso-oxiranes with excellent yields and ee values of up to 87%. Mechanistic aspects of these reactions are considered. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Vrancken, Emmanuel,Alexakis, Alexandre,Mangeney, Pierre
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p. 1354 - 1366
(2007/10/03)
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- Chiral ionic liquids as stationary phases in gas chromatography
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Recently, it has been found that room-temperature ionic liquids can be used as stable, unusual selectivity stationary phases. They show "dual nature" properties, in that they separate nonpolar compounds as if they are nonpolar stationary phases and separate polar compounds as if they are polar stationary phases. Extending ionic liquids to the realm of chiral separations can be done in two ways: (1) a chiral selector can be dissolved in an achiral ionic liquid, or (2) the ionic liquid itself can be chiral. There is a single precedent for the first approach, but nothing has been reported for the second approach. In this work, we present the first enantiomeric separations using chiral ionic liquid stationary phases in gas chromatography. Compounds that have been separated using these ionic liquid chiral selectors include alcohols, diols, sulfoxides, epoxides, and acetylated amines. Because of the synthetic nature of these chiral selectors, the configuration of the stereogenic center can be controlled and altered for mechanistic studies and reversing enantiomeric retention.
- Ding, Jie,Welton, Thomas,Armstrong, Daniel W.
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p. 6819 - 6822
(2007/10/03)
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- Reduction of carbonyl compounds by lanthanide metal/2-propanol: In-situ generation of samarium isopropyloxide for stereoselective Meerwein-Ponndorf- Verley reduction
-
The reduction of ketones and aldehydes with lanthanide metals (La, Ce, Sm, Yb) and a catalytic amount of iodine (5 mol %) in iPrOH proceeded smoothly to produce the corresponding alcohols as the major products in good yield, while in THF, methanol, and ethanol the pinacols were mainly produced. The yields of alcohols were improved most effectively by the use of Sm metal, the amount of pinacol produced thus being minimized. The actual reducing agent may be samarium isopropyloxide, which mediates the Meerwein-Ponndorf-Verley-type hydride-transfer reaction, since the reaction can be carried out catalytically with respect to samarium. The stereoselectivities of the reductions of the 2- and 4-substituted cyclohexanones with Sm/iPrOH were higher than those achieved with SmI2/iPrOH or Sm/ H20. The asymmetric reduction of acetophenone could be achieved to give the 1-phenylethanol in up to 95% ee in the presence of the chiral ligand 7. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Fukuzawa, Shin-Ichi,Nakano, Narihito,Saitoh, Takahide
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p. 2863 - 2867
(2007/10/03)
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- Synthesis and applications of chiral bis-THF in asymmetric synthesis
-
The synthesis of enantiopure bis-THF is described, starting from d-mannitol. Bis-THF is used as chiral ligand for organolithium reagents in four different reactions. The enantioselectivity provided by this ligand is moderate, and the asymmetric induction is in line with the expected model. Graphical Abstract.
- Alexakis, Alexandre,Tomassini, Axel,Leconte, Stéphane
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p. 9479 - 9484
(2007/10/03)
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- A new bismuth nitrate-induced stereospecific glycosylation of alcohols
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Bismuth nitrate-catalyzed stereospecific glycosylation of alcohol with glycal has been developed.
- Banik, Bimal K.,Adler, Dorothy,Nguyen, Phuong,Srivastava, Neeta
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p. 101 - 104
(2007/10/03)
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- Recyclable Polyurea-Microencapsulated Pd(0) Nanoparticles: An Efficient Catalyst for Hydrogenolysis of Epoxides
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(Matrix presented) Pd nanoparticles (~2 nm in size) microencapsulated in polyurea is an efficient and recyclable catalyst for reductive ring-opening hydrogenolysis of epoxides, using either HCOOH/Et3N or H2 as a hydrogen donor.
- Ley, Steven V.,Mitchell, Claire,Pears, David,Ramarao, Chandrashekar,Yu, Jin-Quan,Zhou, Wuzong
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p. 4665 - 4668
(2007/10/03)
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- The design of novel N-4′-pyridinyl-α-methyl proline derivatives as potent catalysts for the kinetic resolution of alcohols
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A novel family of chiral acylation catalysts based on a N-4′-pyridinyl-α-methyl proline structure has been studied. A set of 31 compounds has been easily prepared and screened in the kinetic resolution of racemic alcohol 33 resulting in high enantioselectivities in most cases. From results obtained, H-bonding interactions between the catalyst and the substrate would appear essential to afford high enantioselectivity during the catalytic acylation. Additional solvent dependence and anhydride studies have been made to better identify the mechanism. This work has been further extended to the study of a number of structurally different alcohols. Ethanolamine derivatives in particular were found to be highly effective substrates (up to S = 18.8) in the kinetic resolution.
- Priem, Ghislaine,Pelotier, Béatrice,Macdonald, Simon J. F.,Anson, Mike S.,Campbell, Ian B.
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p. 3844 - 3848
(2007/10/03)
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- Effective nonenzymatic kinetic resolution of (±)-trans-2-arylcyclohexanols using 3β-acetoxyetienic acid, DCC, and DMAP
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(1R,2S)-trans-2-Arylcyclohexanols of high enantiomerically purity were obtained by the simple stirring of the corresponding (±)-arylcyclohexanols with 3β-acetoxyetienic acid, DCC, and DMAP at room temperature.
- Matsugi, Masato,Hagimoto, Yuri,Nojima, Masatomo,Kita, Yasuyuki
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p. 583 - 584
(2013/09/05)
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- A new nucleophilic catalyst for kinetic resolution of racemic sec-alcohols
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A new tertiary amine-based nucleophilic catalyst, derived from a simple combination of commercially available compounds, affords good to excellent kinetic resolution of racemic sec-alcohols.
- Jeong, Kyu-Sung,Kim, Soong-Hyun,Park, Hyun-Jin,Chang, Kyoung-Jin,Kwan, Soo Kim
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p. 1114 - 1115
(2007/10/03)
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- Diastereoselective reduction of alkenylboronic esters as a new method for controlling the stereochemistry of up to three adjacent centers in cyclic and acyclic molecules
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(figure presented) cis-Boronates are readily available via a diastereoselective Pd-catalyzed reduction of tetrasubstituted alkenylboronic esters using H2. Applying the reaction conditions presented to unsaturated open-chain boronic esters allows the stereochemistry of up to three adjacent centers to be controlled.
- Hupe, Eike,Marek, Ilan,Knochel, Paul
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p. 2861 - 2863
(2007/10/03)
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- Free-radical hydroxylation reactions of alkylboronates
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The radical hydroxylation of B-alkylcatecholboranes, easily prepared by hydroboration of olefins, has been investigated. When molecular oxygen was used as oxidizing agent, the corresponding alcohols were obtained directly without alkaline treatment. The presence of Lewis base additives such as Et3N or DABCO has a benefic effect on the selectivity and yield. Alternatively, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) reacts cleanly with B-alkylcatecholboranes to afford alkyl radicals that can be trapped by a second equivalent of TEMPO to give alkoxyamines. Reduction of the alkoxyamines with zinc in acetic acid affords the desired alcohols. The whole procedure is particularly mild and does not require any basic condition. The two approaches presented in this paper are valuable and represent mild alternatives to the classical alkaline oxidation of organoboranes to alcohols.
- Cadot, Christine,Dalko, Peter I.,Cossy, Janine,Ollivier, Cyril,Chuard, Rachel,Renaud, Philippe
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p. 7193 - 7202
(2007/10/03)
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- Mild and selective sodium azide mediated cleavage of p-nitrobenzoic esters.
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[reaction: see text] A mild and selective cleavage of p-nitrobenzoic esters by sodium azide in methanol is reported. This new methodology is mild enough for use with acid- or base-sensitive compounds. No elimination byproducts are formed. Fmoc- and trifluoroacetyl-amino protecting groups, benzyl esters, and ethyl esters remain unaffected. Less reactive compounds are discussed in terms of steric factors, and yields are increased by altering the azide solvation.
- Gomez-Vidal,Forrester,Silverman
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p. 2477 - 2479
(2007/10/03)
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- Synthesis of (+)-1-epiaustraline
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A highly efficient total synthesis of (+)-1-epiaustraline ((+)-1), a tetrahydroxypyrrolizidine alkaloid of the alexine/australine subclass, is described. The key step is a tandem intramolecular [4 + 2]/intermolecular [3 + 2] nitroalkene cycloaddition involving dienylsilyloxy nitroalkene 3 and chiral vinyl ether 4, which establishes four of the five stereocenters present. The final center was installed by a diastereoselective dihydroxylation. Hydrogenolytic unmasking of the nitroso acetal tosylate 17 containing the silyl ether linkage was thwarted by a slow alkylation and an undesired Peterson-type elimination. Prior removal of the silicon moiety by Tamao-Fleming oxidation proceeded in excellent yield and provided a substrate suitable for hydrogenolysis and deprotection. The complete synthesis required only 10 steps to deliver the (+)-1-epiaustraline in 7.0% overall yield.
- Denmark,Cottell
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p. 4276 - 4284
(2007/10/03)
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- Azomethine ylide cycloaddition/reductive heterocyclization approach to oxindole alkaloids: Asymmetric synthesis of (-)-horsfiline
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The intermolecular [3 + 2] with 2(2-nitrophenyl)acrylate dienophiles followed by reductive heterocyclization affords the spiro(indole-pyrrolidine) ring system. Hence, this enable us to accomplish a concise and highly enantioselective synthesis of (-)-horsfiline 1, based on chiral auxiliary-directed π-face discrimination in the 1,3-dipolar cycloaddition of (1S,2R)- 2-phenyl-1-cyclohexyl ester 4f with N-methylazomethine ylide.
- Cravotto,Giovenzana,Pilati,Sisti,Palmisano
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p. 8447 - 8453
(2007/10/03)
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- A polymer-supported proline-based diamine catalyst for the kinetic resolution of racemic secondary alcohols
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The preparation of polymer-supported proline-based diamine catalyst 12 for the kinetic resolution of racemic mixtures of secondary alcohols is described. Not only is the catalyst effective for the resolution of a host of different alcohols, it can also be recovered and reused several times without loss of either activity or selectivity. The catalyst has been used in conjunction with a polymer-supported sequestration strategy, giving rise to an essentially pure mixture of resolved products that can be separated using flash chromatography.
- Clapham,Cho,Janda
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p. 868 - 873
(2007/10/03)
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- Compensation effect between differential activation enthalpy and entropy in subtilisin-catalyzed kinetic resolutions of secondary alcohols
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Thermodynamic parameters for subtilisin-catalyzed kinetic resolutions of secondary alcohols were determined, and a compensation effect between ΔΔH? and ΔΔS? was found. These data are explained in terms of the transition-state model.
- Ema, Tadashi,Yamaguchi, Kunihiro,Wakasa, Yuji,Tanaka, Nobuaki,Utaka, Masanori,Sakai, Takashi
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p. 782 - 783
(2007/10/03)
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- Enantioselective total syntheses of (+)-castanospermine, (+)-6- epicastanospermine, (+)-australine, and (+)-3-epiaustraline
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The total syntheses of the potent glycosidase inhibitors castanospermine ((+)-1), 6-epicastanospermine ((+)-2), australine ((+)-3), and 3- epiaustraline ((+)-4) are described. The syntheses of indolizidine alkaloids (+)-1 and (+)-2 were accomplished in ei
- Denmark, Scott E.,Martinborough, Esther A.
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p. 3046 - 3056
(2007/10/03)
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