- One carbon elongation of the Hajos-Parrish ketone. Synthesis of (+)-(3aS,7aR)-octahydro-3a-hydroxy-7a-methyl-1-methylene-5H-indene-5-o ne
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The difficulties encountered for the C-1 methylenation of Hajos-Parrish (1) and Hajos-Wiechert (2) ketones, were overcome by the use of Conia reaction on their C-5 dithiane derivatives.
- Medarde,Caballero,Tome,Gracia,Boya,San Feliciano
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Read Online
- β-Homoamino acids as catalysts in enantioselective intra- and intermolecular aldol reactions
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β3-Homoamino acids catalyze the intra- (cf. the Hajos-Parrish-Eder-Sauer-Wiechert reaction) as well as the intermolecular aldol reaction. The stereochemical outcome with selectivities of up to 83% ee is reversed in the intramolecular reaction,
- Limbach, Michael
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Read Online
- Synthesis of ent-Cholesterol, the Unnatural Enantiomer
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Cholesterol is ubiquitious in mammals and plays an important role in human health.The unique relationship between enantiomers make ent-cholesterol, the unnatural enantiomer of cholesterol, a valuable new probe of cholesterol function in biochemical systems.We report the first enantioselective total synthesis of ent-cholesterol.
- Rychnovsky, Scott D.,Mickus, Daniel E.
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Read Online
- Protecting-group-free total synthesis of aplykurodinone-1
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A concise, stereoselective, and protecting-group-free total synthesis of aplykurodinone-1 from Hajos-Parrish ketone was described. The synthetic approach features a sequence of aerobic allylic oxidation and elimination of alcohol 9. The key intermediate for this synthesis was formed by a stereoselective intramolecular radical cyclization.
- Tang, Yu,Liu, Ji-Tian,Chen, Ping,Lv, Ming-Can,Wang, Zhen-Zhen,Huang, Yi-Kun
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Read Online
- Inotropic activity of hydroindene amidinohydrazones
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Several hydroindenic derivatives (7a-methyl-2,3,5,6,7,7a-hexahydro-1H-indenes), bearing an amidinohydrazone at C-5 and different moieties at C-1, have been synthesized and evaluated for their inotropic and chronotropic effects on right- and left-guinea-pig-atria activity. Three of them showed the same profile as digoxin, although with lower potency. The effect on Na+,K+ ATPase (NKA) was also evaluated for these three compounds, observing that two of them, with the same absolute configuration as natural cardenolides, are also NKA inhibitors, while the compound with the opposite configuration lacks such an effect. More interestingly, both active compounds act without affecting the cardiac rhythm. This could be related to the selective inhibition of the human α2β1 isozyme (associated with the inotropic effect) with respect to the α1β1 isozyme (associated with the maintenance of basal ionic levels in the cell and the toxic effect of cardenolides).
- Sevillano,Melero,Caballero,Tomé,Lelièvre,Geering,Crambert,Carrón,Medarde,San Feliciano
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Read Online
- Synthesis of Optically Active trans-Cyclononenes. A Possible Approach to Xenicanes
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Two optically active substituted trans-cyclononenes (13a, 13b) were synthesized from the (-)-Hajos-Parrish diketone.This procedure provides a possible approach for the total synthesis of xenicanes, biologically active compounds isolated from marine organi
- Liu, Gui,Smith, Tim. C.,Pfander, Hanspeter
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Read Online
- Construction of key building blocks towards the synthesis of cortistatins
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This work reports the construction of key building blocks towards the synthesis of cortistatins; a family of steroidal alkaloids. Cortistatin A, being a primary target due to its superior biological properties over other congeners, has been prepared by two different synthetic routes. Synthesis of the precursor to the heavily substituted A-ring starting from d-glucose and construction of the DE-ring junction employing a Hajos-Parrish ketone as a chiral pool have been demonstrated. Efforts are underway to assemble these key fragments and build towards the total synthesis of cortistatin A.
- Indu, Satrajit,Kaliappan, Krishna P.,Telore, Rahul D.
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supporting information
p. 2432 - 2446
(2020/04/22)
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- Desymmetrisation of: Meso -diones promoted by a highly recyclable polymer-supported chiral phosphoric acid catalyst
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A polystyrene-supported BINOL-derived chiral phosphoric acid has been applied to the desymmetrisation of meso-diones to produce enantioenriched cyclohexenones. The catalytic resin has proven highly active and robust, giving rise to Hajos-Parrish or Wieland-Miescher type products in good yields and enantioselectivities, while allowing for extended recycling.
- Clot-Almenara, Lidia,Rodríguez-Escrich, Carles,Pericàs, Miquel A.
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p. 6910 - 6914
(2018/02/23)
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- A Highly Active Polymer-Supported Catalyst for Asymmetric Robinson Annulations in Continuous Flow
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The preparation through Robinson annulation of enantiopure building blocks with both academic and industrial relevance, such as the Wieland-Miescher and Hajos-Parrish ketones, has suffered from important drawbacks, such as the need for high catalyst loading or extremely long reaction times. Here we report a heterogenized organocatalyst based on Luo's diamine for fast and broad-scope enantioselective Robinson annulation reactions. The polystyrene-supported diamine 19a enables the high-yield, highly enantioselective preparation of a wide range of chiral bicyclic enones under mild conditions, with reaction times as short as 60 min (batch) or residence times of 10 min (flow). In contrast with its homogeneous counterpart 19b, the catalytic resin 19a experiences a notable increase in catalytic activity with temperature in 2-MeTHF (a 10-fold decrease in reaction times without erosion in enantioselectivity is observed from room temperature to 55 °C). The scope of the transformation in batch mode has been illustrated with 14 examples, including examples only reported in poorly enantioenriched (22n) or in racemic form (22k). Enantiopure 22k has been used as the starting material for a straightforward formal synthesis of the antibiotic and antifeedant sesquiterpene (-)-isovelleral (24). The heterogenized catalyst 19a admits extended recycling (10 cycles) and has been used to develop the first asymmetric Robinson annulations in continuous flow. The potential of the flow process is illustrated by the large-scale preparation of the Wieland-Miescher ketone (65 mmol in 24 h of operation, TON of 117) and by a sequential flow experiment leading to a library of eight enantioenriched diketone compounds.
- Canellas, Santiago,Ayats, Carles,Henseler, Andrea H.,Pericàs, Miquel A.
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p. 1383 - 1391
(2017/08/09)
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- Lipase-catalyzed domino Michael-aldol reaction of 2-methyl-1,3-cycloalkanedione and methyl vinyl ketone for the synthesis of bicyclic compounds
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Synthesis of bicyclic compounds was achieved via a lipase-catalyzed, stereoselective, domino Michael-aldol reaction of 2-methyl-1,3-cycloalkanedione and methyl vinyl ketone. Appropriate reaction conditions, including the type of enzyme, solvent, and temperature, were determined. In addition, the effects of solvent polarity and addtives were investigated. The reaction proceeded in the presence of lipase AS in a solution of 20% acetone in dimethylsulfoxide (DMSO) at 10 °C for 8 days, followed by the addition of p-toluenesulfonic acid (TsOH) to afford bicyclic compounds in 51-83% yields with moderate stereoselectivity. Although this domino Michael-aldol reaction showed only moderate stereoselectivity, even with the acid-supported enhancement of the reaction, these results represent potential new applications for lipase.
- Sano, Kaoru,Kohari, Yoshihito,Nakano, Hiroto,Seki, Chigusa,Takeshita, Mitsuhiro,Tokiwa, Micho,Hirose, Yoshihiko,Uwai, Koji
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- Bifunctional organocatalysts based on a carbazole scaffold for the synthesis of the Hajos-Wiechert and Wieland-Miescher ketones
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Several bifunctional organocatalysts based on a carbazole scaffold containing a chiral amine and a synthetic oxyanion-hole have been synthesized and successfully applied to the synthesis of the Hajos-Wiechert and Wieland-Miescher ketones (up to 99% ee). Both enamine activation and H-bonding donor ability of these catalysts were evaluated by preparing catalysts differing in the nature of the amine [(R,R)-cyclohexanediamine or l-proline], the H-bond donor functional group (sulfonamide or amide) and the number of NH bonds. Modeling studies and an X-ray structure fully support the obtained results.
- Rubio, Omayra H.,Fuentes De Arriba, ángel L.,Monleón, Laura M.,Sanz, Francisca,Simón, Luis,Alcázar, Victoria,Morán, Joaquín R.
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supporting information
p. 1297 - 1303
(2015/03/05)
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- Evolution of a Unified Strategy for Complex Sesterterpenoids: Progress toward Astellatol and the Total Synthesis of (-)-Nitidasin
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Astellatol and nitidasin belong to a subset of sesterterpenoids that share a sterically encumbered trans-hydrindane motif with an isopropyl substituent. In addition, these natural products feature intriguing polycyclic ring systems, posing significant challenges for chemical synthesis. Herein, the evolution of our stereoselective strategy for isopropyl trans-hydrindane sesterterpenoids is detailed. These endeavors included the synthesis of several building blocks, enabling studies toward all molecules of this terpenoid subclass, and of advanced intermediates of our initial route toward a biomimetic synthesis of astellatol. These findings provided the basis for a second-generation and a third-generation approach toward astellatol that eventually culminated in the enantioselective total synthesis of (-)-nitidasin. In particular, a series of substrate-controlled transformations to install the ten stereogenic centers of the target molecule was orchestrated and the carbocyclic backbone was forged in a convergent fashion. Furthermore, the progress toward the synthesis of astellatol is disclosed and insights into some observed yet unexpected diastereoselectivities by detailed quantum-mechanical calculations are provided. Two and a half molecules: Astellatol and nitidasin are polycyclic sesterterpenoids, posing considerable challenges for synthetic chemists. In this full account, the evolution of a synthetic strategy for these and structurally related natural products is given (see scheme). The presented work includes efforts toward a biomimetic synthesis of astellatol, a successful route for the first total synthesis of (-)-nitidasin, and quantum-mechanical investigations into unexpected diastereosectivities.
- Hog, Daniel T.,Huber, Florian M. E.,Jiménez-Osés, Gonzalo,Mayer, Peter,Houk, Kendall N.,Trauner, Dirk
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supporting information
p. 13646 - 13665
(2015/09/22)
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- Pyrimidine-derived prolinamides as recoverable bifunctional organocatalysts for enantioselective inter- and intramolecular aldol reactions under solvent-free conditions
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Chiral L-prolinamides 2 containing the (R,R)- and (S,S)-trans-cyclohexane-1,2-diamine scaffold and a 2-pyrimidinyl unit are synthesized and used as general organocatalysts for intermolecular and intramolecular aldol reactions with 1,6-hexanedioic acid as a co-catalyst under solvent-free conditions. The intermolecular reaction between ketone-aldehyde and aldehyde-aldehyde must be performed under wet conditions with catalyst (S,S)-2b at 10 °C, which affords anti-aldols with high regio-, diastereo-, and enantioselectivities. For the Hajos-Parrish-Eder-Sauer-Wiechert reaction, both diastereomers of catalyst 2 give similar results at room temperature in the absence of water to give the corresponding Wieland-Miescher ketone and derivatives. Both types of reactions were scaled up to 1 g, and the organocatalysts were recovered by extractive workup and reused without any appreciable loss in activity. DFT calculations support the stereochemical results of the intermolecular process and the bifunctional role played by the organocatalyst by providing a computational comparison of the H-bonding networks occurring with catalysts 2a and 2b. The intermolecular ketone-aldehyde and aldehyde-aldehyde aldol reactions and the Hajos-Parrish-Eder-Sauer-Wiechert versions with the employment of chiral L-prolinamides containing the (R,R)- and (S,S)-trans-cyclohexane-1,2-diamine scaffold and a 2-pyrimidinyl unit are successfully performed under solvent-free conditions; WMK = Wieland-Miescher ketone.
- Vizcaíno-Milla, Pascuala,Sansano, José M.,Nájera, Carmen,Fiser, Béla,G?mez-Bengoa, Enrique
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supporting information
p. 2614 - 2621
(2015/04/27)
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- Novel supported and unsupported prolinamides as organocatalysts for enantioselective cyclization of triketones
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A novel prolylsulfonamide derived from ethylene diamine and its supported counterpart has been prepared and tested as enantioselective intramolecular aldol reaction of cyclic and acyclic triketones. Good to excellent yields and enantioselectivities have been obtained in water and under solvent free conditions.
- Pedrosa, Rafael,Andrés, José María,Manzano, Rubén,Pérez-López, César
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supporting information
p. 3101 - 3104
(2013/06/27)
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- The A-CD analogue of 16β,17α-estriol is a potent and highly selective estrogen receptor β agonist
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Selective estrogen receptor β (ERβ) agonists display neuroprotective properties in animal models and hold promise in the treatment of neurodegenerative diseases. In our quest to design, synthesize and evaluate potent and safe ERβ agonists, we focused on m
- Sauvee, Claire,Schaefer, Anja,Sunden, Henrik,Ma, Jian-Nong,Gustavsson, Anna-Lena,Burstein, Ethan S.,Olsson, Roger
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supporting information
p. 1439 - 1442
(2013/11/19)
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- A practical protocol for asymmetric synthesis of wieland-miescher and hajos-parrish ketones catalyzed by a simple chiral primary amine
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This article describes a simple chiral primary amine catalyzed efficient and practical protocol for the large-scale synthesis of Wieland-Miescher and Hajos-Parrish ketones as well as their analogues. Georg Thieme Verlag Stuttgart. New York.
- Xu, Changming,Zhang, Long,Zhou, Pengxin,Luo, Sanzhong,Cheng, Jin-Pei
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p. 1939 - 1945
(2013/07/26)
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- Recoverable silica-gel supported binam-prolinamides as organocatalysts for the enantioselective solvent-free intra- and intermolecular aldol reaction
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Silica-gel supported binam-derived prolinamides are efficient organocatalysts for the direct intramolecular and intermolecular aldol reaction under solvent-free conditions using conventional magnetic stirring. These organocatalysts in combination with benzoic acid showed similar results to those obtained under similar homogeneous reaction conditions using an organocatalyst of related structure. For the intermolecular process, the aldol products were obtained at room temperature and using only 2 equiv of the ketone with high yields, regio-, diastereo- and enantioselectivities. Under these reaction conditions, also the cross aldol reaction between aldehydes is possible. The recovered catalyst can be reused up to nine times providing similar results. More interestingly, these heterogeneous organocatalysts can be used in the intramolecular aldol reaction allowing the synthesis of the Wieland-Miescher and ketone analogues with up to 92% ee, with its reused being possible up to five times without detrimental on the obtained results.
- Ba?ón-Caballero, Abraham,Guillena, Gabriela,Nájera, Carmen,Faggi, Enrico,Sebastián, Rosa María,Vallribera, Adelina
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p. 1307 - 1315
(2013/02/23)
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- Asymmetric synthesis of Wieland-Miescher and Hajos-Parrish ketones catalyzed by an amino-acid-derived chiral primary amine
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This paper describes a simple chiral primary amine-catalyzed highly efficient and practical protocol for the synthesis of both Wieland-Miescher ketone and Hajos-Parrish ketone as well as their analogues. The reaction can be conducted in gram scale with 1%
- Zhou, Pengxin,Zhang, Long,Luo, Sanzhong,Cheng, Jin-Pei
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experimental part
p. 2526 - 2530
(2012/05/05)
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- A-CD estrogens. I. substituent effects, hormone potency, and receptor subtype selectivity in a new family of flexible estrogenic compounds
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Long-term use of estrogen supplements by women leads to an increased risk of breast and uterine cancers. Possible mechanisms include metabolism of estradiol and compounds related to tumor-initiating quinones, and ligand-induced activation of the estrogen receptors ERα and ERβ which can cause cancer cell proliferation, depending on the ratio of receptors present. One therapeutic goal would be to create a spectrum of compounds of variable potency for ERα and ERβ, which are resistant to quinone formation, and to determine an optimum point in this spectrum. We describe the synthesis, modeling, binding affinities, hormone potency, and a measure of quinone formation for a new family of A-CD estrogens, where the A-C bond is formed by ring coupling. Some substituents on the A-ring increase hormone potency, and one compound is much less quinone-forming than estradiol. These compounds span a wide range of receptor subtype selectivities and may be useful in hormone replacement therapy.
- Wright, James S.,Shadnia, Hooman,Anderson, James M.,Durst, Tony,Asim, Muhammad,El-Salfiti, Mohamed,Choueiri, Christine,Pratt, M. A. Christine,Ruddy, Samantha C.,Lau, Rosanna,Carlson, Kathryn E.,Katzenellenbogen, John A.,Obrien, Peter J.,Wan, Luke
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scheme or table
p. 433 - 448
(2011/04/15)
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- Proline imidazolidinones and enamines in Hajos-Wiechert and Wieland-Miescher ketone synthesis
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Readily available aromatic prolinamides obtained from the acid chloride of proline hydrochloride and anilines induce large enantiomeric excesses in intramolecular aldol condensations. Imidazolidinones derived from the reaction of the catalyst and enamines
- de Arriba, ángel L. Fuentes,Simón, Luis,Raposo, César,Alcázar, Victoria,Morán, Joaquín R.
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scheme or table
p. 4841 - 4845
(2009/10/02)
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- STEROID ANALOGUES FOR NEUROPROTECTION
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Provided are steroid analogues functionalized with polar substituents at the C3 and/or C20 positions of the steroid ring system that exhibit improved water solubility. Also provided are pharmaceutical compositions comprising the steroid analogues and methods using the novel steroid analogues for the treatment and prevention of neurodegeneration in a patient following injury to the central nervous system.
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Page/Page column 130
(2009/10/21)
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- Water versus solvent-free conditions for the enantioselective inter- and intramolecular aldol reaction employing l-prolinamides and l-prolinethioamides as organocatalysts
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Organocatalysts 1, derived from L-proline and (1S,2R)-cis-l-aminoindan-2-ol or (R)-l-aminoin-dane, are evaluated as promoters in the direct asymmetric aldol reaction between ketones and aromatic aldehydes in the presence of water and under solvent-free reaction conditions. L-Prolinethioamides 1c and 1d exhibited higher enantioselectivity than the corresponding prolinamides 1a and 1b in the model aldol reaction between cyclohexanone and 4-nitro-benzaldehyde in the presence of 4-nitrobenzoic acid as cocatalyst. In particular, L-prolinethioamide 1d (5 mol%), derived from L-proline and (R)-1-amino-indane, is shown as the most efficient organocatalyst studied promoting the direct aldol reaction of cyclo-alkyl, alkyl, and a-functionalized ketones with aromatic aldehydes in the presence of water and under solvent-free reaction conditions employing only 2 equivalents of nucleophile. Generally, anft-aldol products are obtained in high yields and excellent diastereo- and enantioselectivities (up to > 98/2 until syn, up to 98% ee). Solvent-free conditions give slightly higher dr and ee than using water as solvent. In addition, organocatalyst Id can be easily recovered by extractive work-up and reused. Prolinethio-amide Id (5 mol%) in combination with 4-NO2C6H4CO2H (5 mol%) is also a very effective or-ganocatalytic system for the asymmetric solvent-free intramolecular Haj os-Parrish-Eder-Sauer-Wiechert reaction with comparable or higher levels of enantioselectivity (up to 88% ee) to other reported catalysts in organic solvents.
- Almasi, Diana,Alonso, Diego A.,Balaguer, Andrea-Nekane,Najera, Carmen
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supporting information; scheme or table
p. 1123 - 1131
(2009/12/07)
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- Chiral phosphoric acid catalyzed desymmetrization of meso-1,3diones: Asymmetric synthesis of chiral cyclohexenones
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Chiral effectiveness: The title transformation is applicable to a wide variety of substrates to give chiral cyclohexenones in high yields and with excellent enantioselecti vity (see scheme). To clarity the origin of the enantioselectivity ONIOM calculations were carried out
- Mori, Keiji,Katoh, Takuya,Suzuki, Tohru,Noji, Takuya,Yamanaka, Masahiro,Akiyama, Takahiko
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supporting information; experimental part
p. 9652 - 9654
(2010/04/28)
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- N-Tosyl-(Sa)-binam-L-prolinamide as highly efficient bifunctional organocatalyst for the general enantioselective solvent-free aldol reaction
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N-Tosyl-(Sa)-binam-L-prolinamide (5 mol%) and benzoic acid (1 mol%) were used as catalysts in the enantioselective direct aldol reaction between different ketones and aldehydes under solvent-free conditions in the presence or absence of water. Under these reaction conditions it was possible to reduce the amount of required ketone to two equivalents to give the corresponding aldol products with high yields, regio-, diastereo- and enantioselectivities. The aldol reaction between aldehydes or the intramolecular aldol reaction can be also performed with excellent results. Georg Thieme Verlag Stuttgart.
- Guillena, Gabriela,Nájera, Carmen,Viózquez, Santiago F.
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scheme or table
p. 3031 - 3035
(2009/10/16)
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- Short α/β-peptides as catalysts for intra- and intermolecular aldol reactions
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(Chemical Equation Presented) Short α/β-peptides, containing conformationally restricted cis-β-aminocyclopropylcarboxylic acid units as turn-inducing elements, have been found to be efficient catalysts for inter-and intramolecular aldol reactions. The tripeptide H-(L)-Pro--(L)-Pro-OH was identified to perform especially well in homogeneous and heterogeneous aqueous solutions as well as in organic solvents.
- D'Elia, Valerio,Zwicknagl, Hans,Reiser, Oliver
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p. 3262 - 3265
(2008/09/19)
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- Structural constraints for C2-symmetric heterocyclic organocatalysts in asymmetric aldol reactions
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Asymmetric aldol reactions were studied in the presence of heterocyclic bimorpholine- and bipiperidine-type organocatalysts. Bimorpholine derivatives were found to be more reactive and more selective in intramolecular, as well as intermolecular, reactions.
- Laars, Marju,Kriis, Kadri,Kailas, Tiiu,Mueuerisepp, Aleksander-Mati,Pehk, Tonis,Kanger, Tonis,Lopp, Margus
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p. 641 - 645
(2008/09/20)
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- Prolinamides versus prolinethioamides as recyclable catalysts in the enantioselective solvent-free inter- and intramolecular aldol reactions
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A solvent-free asymmetric and direct anti-aldol reaction of aliphatic ketones with aromatic aldehydes catalyzed by recyclable L-prolineamides and L-prolinethioamides 3 is studied. The L-prolinethioamide 3d (5 mol%), derived from L-Pro and (R)-1-aminoindane, is the most efficient catalyst for this process affording the anti-aldol adducts in high yields with excellent diastereo-and enantioselectivities (up to >98/2 dr, up to 98% ee) at 0°C or room temperature. Prolinethioamide 3d is an effective organocatalyst for the first asymmetric, solvent-free, intramolecular Hajos-Parrish-Eder-Sauer-Wiechert reaction with comparable or higher levels of enantioselectivity (up to 88% ee) to reported catalysts in organic solvents. Moreover, organocatalyst 3d can be easily recovered and reused by a simple acid/base extraction.
- Almasi, Diana,Alonso, Diego A.,Najera, Carmen
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supporting information; experimental part
p. 2467 - 2472
(2009/08/14)
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- Evaluating β-amino acids as enantioselective organocatalysts of the Hajos-Parrish-Eder-Sauer-Wiechert reaction
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A systematic study of the effect of substitution within the β-amino acid framework indicates that both β2- and β3- amino acids catalyse the Hajos-Parrish-Eder-Sauer-Wiechert reaction with poor to reasonable levels of enantioselectivity. These results led to the evaluation of the conformationally constrained β-amino acid (1R,2S)-cispentacin, which catalyses the Hajos-Parrish-Eder-Sauer-Wiechert reaction with comparable or higher levels of enantioselectivity to l-proline. The Royal Society of Chemistry.
- Davies, Stephen G.,Russell, Angela J.,Sheppard, Ruth L.,Smith, Andrew D.,Thomson, James E.
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p. 3190 - 3200
(2008/03/14)
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- Benzimidazole-pyrrolidine/H+ (BIP/H+), a highly reactive organocatalyst for asymmetric processes
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A new chiral benzimidazole-pyrrolidine has been devised, which exhibits excellent activities in aminocatalyzed aldol reactions, leading to aldol products in high yields and enantioselectivities in the presence of an equimolar amount of a Broensted acid. This organocatalyst has demonstrated remarkable reactivities in aldol processes even with equimolar amounts of aldehyde and ketone in THF. A discussion of the role of the Broensted acid as a co-catalyst is provided along with some applications of this new class of organocatalyst in Robinson annelation and α-amination processes. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Lacoste, Eric,Vaique, Emilie,Berlande, Muriel,Pianet, Isabelle,Vincent, Jean-Marc,Landais, Yannick
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p. 167 - 177
(2007/10/03)
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- Synthesis and use of 3,3′-bimorpholine derivatives in asymmetric Michael addition and intramolecular aldol reaction
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The synthesis of 3,3′-bimorpholine and its N-alkyl derivatives is described. These new diamine derivatives were revealed to be efficient organocatalysts for the asymmetric Michael addition of aldehydes to nitroalkenes with excellent enantioselectivity (up to 90% ee). The potential of these organocatalysts was also demonstrated for the highly enantioselective intramolecular aldol reaction affording the Wieland-Miescher ketone with tremendous enantioselectivity (up to 95% ee). Georg Thieme Verlag Stuttgart.
- Sulzer-Mosse, Sarah,Laars, Marju,Kriis, Kadri,Kanger, Tonis,Alexakis, Alexandre
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p. 1729 - 1732
(2008/02/08)
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- Enantioselective synthesis of Wieland-Miescher ketone through bimorpholine-catalyzed organocatalytic aldol condensation
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Novel bimorpholine-derived organocatalysts have been used for highly enantioselective intramolecular aldol reaction affording Wieland-Miescher ketone in high yield and enantioselectivity (up to 92% and 95%, respectively). Georg Thieme Verlag Stuttgart.
- Kriis, Kadri,Kanger, T?nis,Laars, Marju,Kailas, Tiiu,Müürisepp, Aleksander-Mati,Pehk, T?nis,Lopp, Margus
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p. 1699 - 1702
(2008/02/03)
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- Enzymatic Baeyer-Villiger oxidation of bicyclic diketones
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Cyclohexanone monooxygenase from Acinetobacter calcoaceticus was employed for the Baeyer-Villiger oxidation of racemic bicyclic diketones such as the Wieland-Miescher and the Hajos-Parrish diketones and of some of their derivatives. The corresponding lactones were produced in a highly regio-and enantioselective manner. The reactions were carried out using a crude enzyme preparation in aqueous buffer, at room temperature, and the recycling of the expensive coenzyme NADPH was conducted with a second ancillary enzymatic system. The enzymatic process was simple and easy to handle, thus providing a very practical tool to access enantiopure lactones.
- Ottolina, Gianluca,De Gonzalo, Gonzalo,Carrea, Giacomo,Danieli, Bruno
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p. 1035 - 1040
(2007/10/03)
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- Highly enantioselective organocatalysis of the Hajos-Parrish-Eder-Sauer- Wiechert reaction by the β-amino acid cispentacin
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The β-amino acid cispentacin promotes the Hajos-Parrish-Eder-Sauer- Wiechert reaction with levels of enantioselectivity comparable to or higher than proline. The Royal Society of Chemistry 2005.
- Davies, Stephen G.,Sheppard, Ruth L.,Smith, Andrew D.,Thomson, James E.
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p. 3802 - 3804
(2007/10/03)
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- Enantiomerically Pure Octahydronaphthalenone and Octahydroindenone: Elaboration of the Substrate Overcame the Specificity of Yeast-Mediated Reduction
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Substrate specificity on the reduction of bicyclic diketones with a yeast strain, Torulaspora delbrueckii IFO10921, was investigated. Although this yeast efficiently reduces the isolated carbonyl group involved in the (S)-enantiomer of Wieland-Miescher ke
- Fuhshuku, Ken-Ichi,Tomita, Mina,Sugai, Takeshi
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p. 766 - 774
(2007/10/03)
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- Kinetic and stereochemical evidence for the involvement of only one proline molecule in the transition states of proline-catalyzed intra- and intermolecular aldol reactions
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Contrary to the widely accepted mechanism of the Hajos-Parrish-Eder-Sauer-Wiechert reaction, we have obtained evidence for the involvement of only one proline molecule in the transition states of both inter- and intramolecular aldol reactions. Our conclusions are based on kinetic measurements and the absence of nonlinear and dilution effects on the asymmetric catalysis, and are supported by B3LYP/6-31G* calculations. Complementary to recent theoretical studies, our results provide the foundation of a unified enamine catalysis mechanism of proline-catalyzed inter- and intramolecular aldol reactions. Copyright
- Hoang, Lihn,Bahmanyar,Houk,List, Benjamin
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- Asymmetric one-pot Robinson annulations
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One-pot syntheses of ketol SS-5a, enone S-2 and optically active spiroenediones S-14, R-7 and S-15 are reported.
- Rajagopal,Narayanan,Swaminathan
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p. 4887 - 4890
(2007/10/03)
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- Toward the total synthesis of variecolin
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(matrix presented) An annulative approach toward the total synthesis of the sesterterpenoid variecolin (1) is presented. Synthesis of the key hemiketal, containing the core ABC ring skeleton, has been achieved on a model system by an expeditious route uti
- Molander, Gary A.,Quirmbach, Michael S.,Silva Jr., Luiz F.,Spencer, Keith C.,Balsells, Jaume
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p. 2257 - 2260
(2007/10/03)
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- Efficient kinetic resolution of (±)-4-methyl-Hajos-Parrish ketone by baker's yeast reduction
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Kinetic resolution of (±)-4-methyl-Hajos-Parrish ketone (±)-2a using baker's yeast reduction was investigated. The reaction rate and enantiomeric purity depended on the concentration of substrate and yeast. Under concentrated conditions, (-)-2a and the alcohol (+)-3 were obtained in high enantiomeric excess. Copyright (C) 2000 Elsevier Science Ltd.
- Hioki, Hideaki,Hashimoto, Takefumi,Kodama, Mitsuaki
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p. 829 - 834
(2007/10/03)
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- Regioselective annulation of 1,5-diketones: Access to functionalized Hagemann's esters
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The synthesis of the 'functionalized' Hagemann's ester (S)-18 was investigated. The common starting material in these approaches was enamino ester (S,Z)-5, which was prepared through the condensation of keto diester 4 with (S)-1-phenylethylamine. The Michael addition reaction of 5 with methyl vinyl ketone gave the expected adduct (S)-6 with an ee ≥ 95%. However, all attempts at annulation of 6 invariably afforded the unwanted cyclohexenone derivatives 7 or 8. The addition of 5 to Nazarov reagent 9 furnished adduct (S)-10 with an ee ≥ 95%. The Triton B-induced annulation of 10 unexpectedly gave aldol 11. Depending on the reaction conditions, annulation of 11 afforded either the bicyclic lactone 12, or cyclohexenones 13 or 15. An efficient way of reversing the sense of the regiochemistry of the previous annulation was found, based on the use of diethyl 2-oxo-3-vinylphosphonate (16) as a Michael acceptor. Thus, the condensation of 5 with 16 gave (S)-17 with an ee ≥ 95%, and cyclization of (S)-17 under Horner-Wadsworth-Emmons conditions gave the desired Hagemann's ester (S)-18. The structural assignments for 18 were ascertained by chemical correlation with the known hydrindenedione (S)-21.
- Gassama, Abdoulaye,D'Angelo, Jean,Cave, Christian,Mahuteau, Jacqueline,Riche, Claude
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p. 3165 - 3169
(2007/10/03)
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- Use of Winterfeldt's template to control the C-2' configuration in the synthesis of strigol-type compounds
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A route comprising (i) a cycloaddition reaction of citraconic anhydride with the Winterfeldt auxiliary, (ii) hydride reduction of the cycloadduct, (iii) a (formal) ether formation, and (iv) a cycloreversion reaction allows efficient stereocontrol at C-2' in the synthesis of strigol and its structural analogues.
- Roehrig, Susanne,Hennig, Lothar,Findeisen, Matthias,Welzel, Peter,Mueller, Dietrich
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p. 3439 - 3456
(2007/10/03)
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- Asymmetric Michael addition of malonate anions to prochiral acceptors catalyzed by L-proline rubidium salt
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L-Proline rubidium salt catalyzes the asymmetric Michael addition of malonate anions to prochiral enones and enals. This method can be applied to a wide range of substrates to give adducts with a predictable absolute configuration: (S)-adducts from (E)-enones/enals and (R)-adducts from cyclic (Z)-enones. Both the secondary amine moiety and the carboxylate moiety are critical for the catalytic activity and asymmetric induction. Varying the countercation also affects the reaction course. High enantiomeric excesses were attained when di(tert-butyl) malonate was added to (E)-enones in the presence of CsF. The stereochemistry of the Michael reaction indicates that asymmetric induction takes place via enantioface discrimination involving the acceptor α-carbon atom rather than the β-carbon atom.
- Yamaguchi, Masahiko,Shiraishi, Tai,Hirama, Masahiro
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p. 3520 - 3530
(2007/10/03)
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- Asymmetric synthesis without solvent
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Asymmetric syntheses of the diketones S-1, S-6, and S-10 from the precursors 3, 5 and 8 respectively have been carried out in the abscence of solvent employing S-proline as chiral auxiliary.
- Rajagopal, Desikan,Rajagopalan,Swaminathan
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p. 2189 - 2190
(2007/10/03)
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- Asymmetric synthesis of organic compounds
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Optically active organic compounds are prepared starting from optically inactive reactants by means of an optically active agent which influences the course of the reaction. In particular optically active compounds having a "meso" type carbon atom undergo an intramolecular ring closure in the presence of an optically active agent to yield an optically active product having one additional ring. The present process is particularly useful in the preparation of optically active bicyclic diketones which are important intermediates in the total synthesis of steroids.
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