- A Formal Synthesis of Ptaquilosin. The Aglycon of a Potent Bracken Carcinogen Ptaquiloside
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A formal synthesis of racemic and optically active ptaquilosin has been achieved from the commercially available methyl 2-oxocyclopentanecarboxylate.
- Cossy, Janine,Ibhi, Said,Kahn, Philippe H.,Tacchini, Laura
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- Formal total synthesis of (?)-hamigeran B from a chemo-enzymatically prepared building block with quaternary chiral center
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A formal total synthesis of (?)-hamigeran B was achieved in 17 steps from commercially available ethyl 2-oxocyclopentanecarboxylate. Carbonyl reductase-catalyzed asymmetric reduction and the subsequent chemical transformations furnished an enantiomerically pure synthetic intermediate, (R)-5-formyl-2-isopropyl-5-methylcyclopent-1-en-1-yl trifluoromethylsulfonate. Suzuki-Miyaura coupling with Gao's arylboronate [2-(2-formyl-3-methoxy-5-methylphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane], under PdCl2(dppf)?CH2Cl2 catalysis, and the subsequent cyclization by way of intramolecular reductive SmI2-mediated 1,2-diol formation provided a tricyclic skeleton with a tetrasubstituted double bond between C-1 and C-9b. Upon hydrogenation of this double bond, the proper stereochemistry of the remaining chiral centers was established. Exclusive addition of the hydrogen atom from the β-face occurred, owing to the shielding of the α-face with a bulky TBS protective group on the C-4 alcohol. The hydrogenation products were transformed into Clive's synthetic precursor for (?)-hamigeran B.
- Kuwata, Kazuaki,Fujita, Rie,Hanaya, Kengo,Higashibayashi, Shuhei,Sugai, Takeshi
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- Is the ring conformation the most critical parameter in lipase-catalysed acylation of cycloalkanols?
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CAL-B catalysed the resolution of several five and six-membered cyclic β-hydroxy esters efficiently with the exception of the cis-cyclohexanol (±)-4. When employing molecular modelling techniques the conformation turned out to be the most important determ
- Levy, Laura M.,Lavandera, Ivan,Gotor, Vicente
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- Investigation of Electrostatic Interactions towards Controlling Silylation-Based Kinetic Resolutions
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Electrostatic interactions between a silylated isothiourea intermediate and an ester π system were explored by determining how variations in sterics and electronics affect the selectivity of a silylation-based kinetic resolution. Sterics on the π systems affect the selectivity factors of alkyl 2-hydroxycyclohexanecarboxylates, resulting in a strong correlation of selectivity factors to Charton values. Induction effects of electron-withdrawing substituents on phenyl esters significantly enhance selectivity supporting an edge to face π–π interaction. The linear free energy relationships that were uncovered will aid in future incorporation of intermolecular electrostatic interactions towards controlling asymmetric reactions.
- Zhang, Tian,Redden, Brandon K.,Wiskur, Sheryl L.
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supporting information
p. 4827 - 4831
(2019/08/12)
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- Copper-catalyzed, stereoconvergent,: Cis -diastereoselective borylative cyclization of ω -mesylate- α, β -unsaturated esters and ketones
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The Cu(i)-catalyzed stereoconvergent borylative cyclization of ω-mesylate-α,β-unsaturated compounds is facilitated by a simple Cu-bisphosphine catalyst. This reaction provides a novel route to cis-β-boron-substituted five- and six-membered carbocycle and heterocycle esters. Mechanistic studies indicate that stereoconvergence and cis-substitution likely stem from the rapid enolation of the borylcopper adduct with the substrate double bond and the formation of a five-membered intermediate, respectively.
- Zuo, Ya-Jie,Chang, Xiao-Tong,Hao, Zhi-Ming,Zhong, Chong-Min
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p. 6323 - 6327
(2017/08/10)
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- Chemo-enzymatic synthesis of (R)-5-hydroxymethyl-2-isopropyl-5-methylcyclopent-1-en-1-yl trifluoromethylsulfonate, a potential chiral building block for multicyclic terpenoids
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The chemo-enzymatic synthesis of (R)-5-hydroxymethyl-2-isopropyl-5-methylcyclopent-1-en-1-yl trifluoromethylsulfonate, a potential chiral building block for polycyclic terpenoids containing a five–membered ring having isopropyl and angular methyl substituents, such as erinacin A and dolatriol, was achieved over 11 steps from ethyl 2-oxocyclopentane-1-carboxylate. The key synthetic precursor for this triflate was ethyl (1S,2R)-2-hydroxycyclopentanecarboxylate (>99% ee), which was prepared by a lipase-catalyzed enantioselective hydrolysis of the corresponding racemic acetate. The antipodal (S)-triflate is expected to be the synthetic intermediate for another group of terpenoids involving hamigeran B and stolonidiol. Enantiomerically pure (1R,2S)-hydroxyester (>99% ee) was prepared in high yield using the asymmetric reduction of the oxoester with commercially available carbonyl reductase, “Chiralscreen OH”-E001.
- Kuwata, Kazuaki,Hanaya, Kengo,Sugai, Takeshi,Shoji, Mitsuru
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p. 964 - 968
(2017/07/11)
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- The fluoroalkene motif as a surrogate of the amide bond: Syntheses of AA-Ψ[(Z) and (E)-CFCH]-Pro pseudodipeptides and an Enalapril analogue
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This work describes the optimization process for the synthesis of pseudodipeptides featuring a proline bound to another amino acid through a fluoroalkene moiety that act as an amide bond surrogate. The synthetic methodology is extended to non-peptidic molecules as demonstrated in the design and synthesis of an Enalapril analogue.
- Villiers, Emilie,Couve-Bonnaire, Samuel,Cahard, Dominique,Pannecoucke, Xavier
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p. 7054 - 7062
(2015/08/19)
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- Candida antarctica lipase B-catalyzed reactions of β-hydroxy esters: Competition of acylation and hydrolysis
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The ester function of ethyl cis-(±)-2-hydroxycyclopentane-1- carboxylate [(±)-1] and ethyl (±)-5-hydroxycyclopent-1- enecarboxylate [(±)-2] was demonstrated to undergo hydrolysis, as a side-reaction, during asymmetric (E > 200) O-acylation with Candida antarctica lipase B (CAL-B) as catalyst and vinyl acetate as acyl donor in t-BuOMe at 30 C. This competition of acylation and undesirable hydrolysis draws attention to CAL-B-catalyzed non-hydrolytic resolutions where the substrates contain any hydrolysable functions. Enantiomerically enriched cis-2-hydroxycyclopentane-1-carboxylic acid (ee = 90%) and 5-hydroxycyclopent-1- enecarboxylic acid (ee = 47%) were prepared through de novo CAL-B-catalyzed hydrolysis of (±)-1 and (±)-2 with added H2O in t-BuOMe at 30 C.
- Forro, Eniko,Galla, Zsolt,Fueloep, Ferenc
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- Straightforward asymmetric synthesis of Ala-Ψ[CF=CH]-pro, a proline-containing pseudodipeptide bearing a fluoroolefin as a peptide bond mimic
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From ethyl-2-oxocyclopentanecarboxylate, we developed an asymmetric synthesis of the fluorinated dipeptide Ala-Ψ[(Z)CFCH]-Pro analogue of the transoid parent dipeptide. The fluorinated pseudodipeptide could be incorporated into various peptides or proteins for conformational, structural studies and biological activity studies and could also play a relevant role as an enzyme inhibitor.
- Dutheuil, Guillaume,Pierry, Camille,Villiers, Emilie,Couve-Bonnaire, Samuel,Pannecoucke, Xavier
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p. 1320 - 1325
(2013/05/22)
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- Synthesis of isopeptide epoxide peptidomimetics
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Two epoxide-containing peptidomimetics of the isopeptide, glutamyl-γ-glutamate, have been synthesized via a route that should be generally applicable to the synthesis of isopeptide analogues in which an oxirane replaces the scissile peptide bond. Enzymes
- Majumdar, Debatosh,Alexander, Matthew D.,Coward, James K.
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scheme or table
p. 617 - 627
(2009/06/28)
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- Reductions of cyclic β-keto esters by individual Saccharomyces cerevisiae dehydrogenases and a chemo-enzymatic route to (1R,2S)-2-methyl-1-cyclohexanol
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Twenty purified dehydrogenases cloned from bakers' yeast (Saccharomyces cerevisiae) and expressed as fusion proteins with glutathione (S)-transferase were tested for their ability to reduce three homologous cyclic β-keto esters. The majority of dehydrogenases reduced ethyl 2-oxo-cyclopentanecarboxylate, yielding a pair of diastereomeric alcohols with consistent (1R)-stereochemistry. Ethyl 2-oxo-cyclohexanecarboxylate reductions afforded only cis-alcohol enantiomers. Ethyl 2-oxo-cycloheptanecarboxylate was accepted by two enzymes in the collection, and both yielded mainly the cis-(1R,2S)-alcohol. Escherichia coli cells overexpressing the YDL124w gene were used in a dynamic kinetic resolution of ethyl 2-oxo-cyclohexanecarboxylate to produce the key intermediate in a chemo-enzymatic synthesis of (1R,2S)-2-methyl-1-cyclohexanol, an important chiral building block.
- Padhi, Santosh Kumar,Kaluzna, Iwona A.,Buisson, Didier,Azerad, Robert,Stewart, Jon D.
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p. 2133 - 2138
(2008/02/11)
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- Asymmetric hydrogenation of β-keto esters using chiral diphosphonites
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The BINOL-derived diphosphonite having an achiral backbone based on diphenyl ether is a readily accessible and cheap ligand for the enantioselective Ru-catalyzed hydrogenation of β-keto esters (ee = 95-99%).
- Reetz, Manfred T.,Li, Xiaoguang
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p. 1157 - 1160
(2007/10/03)
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- A recombinant ketoreductase tool-box. Assessing the substrate selectivity and stereoselectivity toward the reduction of β-ketoesters
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The substrate selectivity and stereoselectivity of a series of ketoreductases were evaluated toward the reduction of two sets of β-ketoesters. Both the structural variety at β-position and the substituent at α-position greatly affected the activity and stereoselectivity of these ketoreductases. For the first set of β-ketoesters, at least one ketoreductase was found that catalyzed the formation of either (d) or (l) enantiomer of β-hydroxyesters from each substrate with high optical purity, with the only exception of ethyl (d)-3-hydroxy-3-phenylpropionate. For the second set of β-ketoesters with α-substituents, the situation is more complex. More commonly, a ketoreductase was found that formed one of the four diastereomers in optically pure form, with only a few cases in which enzymes could be found that formed two or more of the diastereomers in high optical purity. The continued development of new, more diverse ketoreductases will create the capability to produce a wider range of single diastereomers of 2-substituted-3-hydroxy acids and their derivatives.
- Zhu, Dunming,Mukherjee, Chandrani,Rozzell, J. David,Kambourakis, Spiros,Hua, Ling
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p. 901 - 905
(2007/10/03)
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- Regioselective synthesis of α-methyl 2-methyleneglutarate via a novel lactonization-elimination rearrangement
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A facile route to the α-methyl ester of 2-methyleneglutarate via a three-step sequence from 3-hydroxymethylcyclopentene is described. Regioselective formation of the monoacid from a diester precursor proceeds via a novel fluoride-mediated, tandem deprotection/rearrangement of O-silyl 2-(hydroxymethyl)dimethylglutarate.
- Hartley, David M.,Coward, James K.
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p. 372 - 374
(2007/10/03)
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- Enzymatic process for the preparation of optically active alcohols from ketones using tuberous root Daucus carota
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The present invention relates to an enzymatic process for the preparation of optically active chiral alcohols using tuberous root Daucus carota; particularly invention relates to an enzymatic process for the preparation of optically active alcohols by enantioselective reduction of corresponding ketones using tuberous root Daucus carota.
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Page/Page column 6; 9
(2008/06/13)
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- A stereoselective synthesis of phosphinic acid phosphapeptides corresponding to glutamyl-γ-glutamate and incorporation into potent inhibitors of folylpoly-γ-glutamyl synthetase
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Radical addition of H3PO2 to N-/C-protected vinyl glycine led to the corresponding H-phosphinic acid in excellent yield. The non-nucleophilic H-phosphinic acid was converted to a nucleophilic P III species, RP(OTMS)2, which was used in two approaches to the target phosphinic acid containing pseudopeptide. New methodology was developed that led to excellent yields in the reaction of RP(OTMS)2 with unactivated electrophiles, including an acyclic homoallylic bromide. However, en route to the target pseudopeptide, Arbuzov reaction of RP(OTMS) 2 with a cyclic homoallylic bromide, (R)-3-(bromomethyl)-cyclopent-1- ene, led to a rearranged allylic phosphinic acid rather than the desired homoallylic derivative, a putative glutarate surrogate. Conjugate addition of RP(OTMS)2 to α-methylene glutarate containing a chiral auxiliary resulted in only modest diastereoselectivity. Purification by flash chromatography provided protected derivatives of both diastereomers of the pseudopeptide. Following global deprotection, coupling of (S)-H-Glu-γ- [Ψ(P(O)(OH)(CH2))]-(S)-Glu-OH and (S)-H-Glu-γ-[Ψ(P(O) (OH)(CH2))]-(R)-Glu-OH to (4-amino-4-deoxy-10-methyl)pteroyl azide led to the target compounds for biochemical study as inhibitors of the ATP-dependent ligase, folylpoly-γ-glutamate synthetase.
- Hartley, David M.,Coward, James K.
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p. 6757 - 6774
(2007/10/03)
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- New efficient synthesis of Taniaphos ligands: Application in ruthenium- and rhodium-catalyzed enantioselective hydrogenations
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A third generation of Taniaphos 1,5-diphosphine ferrocene ligands with the new and interesting (SFc,3S)- and (RFc,3R)-configurations has been prepared. With these ligands, the ruthenium-catalyzed hydrogenation of C=O bonds proceeded with high diastereo- and enantioselectivity (up to >99% de and 97% ee). Good results were also obtained for the rhodium-catalyzed hydrogenation of C=C (up to 96% ee) and C=N bonds (up to 65% ee).
- Tappe, Katja,Knochel, Paul
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- Immobilized baker's yeast reduction in fluorous media
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The first example of immobilized bakers' yeast mediated reduction of ketones in fluorous media is described. The use of fluorous media permits simple work-up and reuse of the solvent without any purification.
- Yajima, Arata,Naka, Kazumi,Yabuta, Goro
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p. 4577 - 4579
(2007/10/03)
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- Lipase-catalysed resolution of cyclic cis- and trans-β-hydroxy esters
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Lipases A and B from Candida antarctica are shown to be highly efficient and complementary biocatalysts for the resolution of five- to seven-membered cyclic β-hydroxy esters by O-acylation. Using this procedure, all four stereoisomers of each one are obtained in enantiopure form and very high yields.
- Levy, Laura M.,Dehli, Juan R.,Gotor, Vicente
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p. 2053 - 2058
(2007/10/03)
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- Synthesis of a new class of chiral 1,5-diphosphanylferrocene ligands and their use in enantioselective hydrogenation
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A new family of ferrocenylphosphane ligands has been prepared. Their flexible synthesis allows many structural modifications. The asymmetric induction of these ligands was examined in the hydrogenation of functionalized C=C, C=O, and C=N bonds. The enantioselectivity of the reaction was strongly dependent on the substituent R at the position α to the ferrocene moiety. In many cases, both enantiomeric β-hydroxyesters of the reduction product can be obtained by simply replacing a dimethylamino group in the ligand with a methyl group.
- Ireland, Tania,Tappe, Katja,Grossheimann, Gabi,Knochel, Paul
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p. 843 - 852
(2007/10/03)
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- Efficient enantioselective reduction of ketones with Daucus carota root
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A novel and efficient reduction of various prochiral ketones such as acetopehones, α-azido aryl ketones, β-ketoesters, and aliphatic acyclic and cyclic ketones to the corresponding optically acive secondary alcohols with moderate to excellent chemical yield was achieved by using Daucus carota, root plant cells under extremely mild and environmentally benign conditions in aqueous medium, has been described. Many of these optically active alcohols are the potential chiral building blocks for the synthesis of pharmaceutically important molecules and asymmetric chiral ligands. Hence, this biocatalytic approach is found to be the most suitable for the preparation of a wide range of chiral alcohols and gave inspiration for the development of a new biotechnological process.
- Yadav,Nanda,Thirupathi Reddy,Bhaskar Rao
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p. 3900 - 3903
(2007/10/03)
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- Immobilized baker's yeast reduction of ketones in an ionic liquid, [bmim]PF6 and water mix
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The bioreduction with immobilized baker's yeast of several ketones was carried out in a 10:1 [bmim]PF6 ionic liquid/water mix. The reductions produced alcohols with comparable enantioselectivities to baker's yeast reductions in alternative media.
- Howarth, Joshua,James, Paraic,Dai, Jifeng
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p. 7517 - 7519
(2007/10/03)
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- A novel highly stereoselective synthesis of chiral 5- and 4,5-substituted 2-oxazolidinones
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A novel highly stereoselective synthesis of chiral mono- and bicyclic 4- and 4,5-substituted 2-oxazolidinones starting from β-keto esters was developed. After bioreduction with S. cerevisiae the resulting homochiral β-hydroxy esters are transformed into their hydrazides. Treatment with NaNO2/H+ then furnishes 2-oxazolidinones in high e.e. (~99%) and d.e. (>99%). The ring formation proceeds via a highly concerted sextet rearrangement with full retention of configuration at the stereocentres. Enantiopure 1,2-amino alcohols can subsequently be obtained by saponification of the 2-oxazolidinone products.
- Bertau,Buerli,Hungerbuehler,Wagner
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p. 2103 - 2107
(2007/10/03)
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- Synthetic studies on halichlorine and pinnaic acid: Palladium-mediated construction of the bicyclic spiro core
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Palladium-mediated cyclization of 19 and 23 directed toward the construction of the bicyclic core (3), which would serve as a key intermediate for the total synthesis of halichlorine (1) and pinnaic acid (2), was explored and found to proceed for 19 in a
- Yokota, Wakako,Shindo, Mitsuru,Shishido, Kozo
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p. 871 - 885
(2007/10/03)
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- Rhodium-catalyzed reformatsky-type reaction
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(equation presented) A novel Reformatsky-type reaction was developed using RhCl(PPh3)3 and diethylzinc. Inter- and intramolecular Reformatsky-type reactions were achieved efficiently under mild reaction conditions to give β-hydroxy esters.
- Kanai, Kazuo,Wakabayashi, Hitoshi,Honda, Toshio
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p. 2549 - 2551
(2007/10/03)
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- Enantioselective ruthenium-mediated hydrogenation: Developments and applications
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A general preparation of chiral ruthenium(II) catalysts and the homogeneous enantioselective hydrogenation of prochiral olefins and keto groups are presented. Some applications to the synthesis of biologically active compounds are reported.
- Ratovelomanana-Vidal, Virginie,Genet, Jean-Pierre
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p. 163 - 171
(2007/10/03)
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- A new synthesis of (-)-frontalin, the bark beetle pheromone
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(-)-Frontalin [(1S,5R)-1,5-dimethyl-6,8-dioxabicyclo[3.2.1]-octane (1)] was synthesized from ethyl 2-oxocyclopentane-1-carboxylate (2) as the starting material. Baker's yeast was used for the asymmetric reduction of 2 to 3. The S configuration at C-1 of 1 was generated by diastereoselective methylation of the dianion derived from 3 to give 4. The present process furnished about 10 g of 1 with enantiomeric purity of 89.1% e.e.
- Nishimura, Yutaka,Mori, Kenji
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p. 233 - 236
(2007/10/03)
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- Asymmetric alkylations and aldol reactions: (1S,2R)-2-aminocyclopentan-1-ol derived new chiral auxiliary
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Asymmetric alkylation and aldol reaction of optically active (1S,2R)-2-aminocyclopentan-1-ol derived chiral auxiliary proceeded with excellent diastereofacial selectivities (>99%) and isolated yields.
- Ghosh, Arun K.,Cho, Hanna,Onishi, Masanobu
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p. 821 - 824
(2007/10/03)
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- A chemoenzymatic preparation of both enantiomers of ω-hydroxymethyl-substituted lactones
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(R)- and (S)-δ-hydroxymethyl valerolactone and ε-hydroxymethyl caprolactone were prepared as tert-butyldiphenylsilyl derivatives, in good yield and high enantiomeric purities, in a 5 step sequence, starting from the microbial stereospecific reduction of ethyl 2-oxocyclopentane or 2-oxocyclohexane carboxylates respectively.
- Buisson, Didier,Azerad, Robert
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- Bryophyte constituents; 6: Synthesis of herbertene-derived sesquiterpenes from Herberta adunca
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Efficient total syntheses are described for the racemic sesquiterpenes herbertenolide (2), α-herbertenol (3) and β-herbertenol (4) from Herberta adunca. ent-Herbertenolide [(+)-2] was prepared from enantiopure (-)-ethyl (1R)-1-methyl-2-oxocyclopentanecarboxylate (9) obtained from ethyl 2-oxocyclopentanecarboxylate (19) via reduction with baker's yeast.
- Eicher, Theophil,Servet, Frank,Speicher, Andreas
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p. 863 - 870
(2007/10/03)
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- Purification and Characterization of Ethyl 2-Methyl-3-oxobutanoate Reductase from Klebsiella pneumoniae IFO3319
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An enzyme that catalyzes a reduction of ethyl 2-methyl-3-oxobutanoate (1) to ethyl (2R,3S) 3-hydroxy-2-methylbutanoate was found in Klebsiella pneumoniae IFO 3319 cells. The enzyme was isolated from the cells and purified 250-fold by ammonium sulfate frac
- Miya, Hiroyuki,Kawada, Mitsuru,Sugiyama, Yoshio
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p. 760 - 764
(2007/10/03)
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- Synthesis of Optically Active α-Methylene γ-Butyrolactones and (+)-Mintlactone
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The combination of baker's yeast reductions of β-keto carbonyls, vinyl triflate formation and a palladium-catalysed, intramolecular, carbonylative coupling affords optically active α-methylene γ-butyrolactones.The synthesis of the unnatural (+)-mintlacton
- Crisp, Geoffrey T.,Meyer, Adam G.
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p. 5831 - 5846
(2007/10/02)
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- Stereoselective Reduction of Thiocarbonyl Compounds with Baker's Yeast
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Alkyl esters of 3-thioxo-butanoic, -pentanoic and -hexanoic acid, 2-thioxo-1-cyclopentanecarboxylic acid ethyl ester, and 2-octanethione have been reduced with baker's yeast to give optically active thiols.The reductions parallel those of the oxygen analogues with respect to rate and diastereo- and enantioselectivity but, generally, the enantiomeric excess (ee) values are smaller.The influence of experimental variables such as substrate concentration, physiological condition of the yeast (resting/fermenting, fresh/dry/frozen), substrate modification, and addition of inhibitors on stereoselectivity has been studied.The formation of S-products was favoured by small substrate concentrations, use of dry or frozen yeast, and by addition of R-enzyme inhibitors (ethyl acrylate and biacetyl).The yields of thiol products are limited by extensive hydrolysis of the thioxo groups of all substrates used.In order to make meaningful comparisons of enantiomeric preferences in baker's yeast reduction of different substrates it is suggested that the maximum ee values reached below certain (substrate dependent) substrate/yeast ratios are used.
- Nielsen, Jens Kaergaard,Madsen, Joergen Oegaard
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p. 403 - 410
(2007/10/02)
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- Dynamic kinetic resolution of cyclic β-ketoesters with preformed or prepared in situ chiral diphosphine-ruthenium (II) catalysts
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The reduction of racemic β-keto esters having the tetralone structure by chiral ruthenium(II) catalysts is realized with an ideal kinetic dynamic resolution. Remarkably, high anti selectivity approaching 100% and enantioselectivity (up to 97%) using atrop
- Genet,Pfister,Ratovelomanana-Vidal,Pinel,Laffitte
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p. 4559 - 4562
(2007/10/02)
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- Preparation of (R)-(2-cyclopentenyl)methanol and the first total synthesis of (8R,11R)-precapnelladiene
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Enantiometrically pure (R)-(2-cyclopentenyl)methanol (2) was prepared from ethyl 2-oxocyclopentanecarboxylate. Coupling of 2 with 4,4-dimethyl-3-phenylthio-2-cyclohexenone gave an enol ether, which was converted into (8R,11H)-precapnelladiene, [α](D)19 = -70.7°, in 6 steps.
- Maeda,Inouye
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p. 2880 - 2882
(2007/10/02)
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- Optically active compounds, liquid crystal compositions comprising said compounds and liquid crystal optical modulators using said compositions
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The invention relates to optically active compounds represented by the general formula STR1 wherein R1, R2, Q1, Q2, Q3, STR2 and M are defined as in the specification, methods and intermediates for th
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- Chemo-enzymatic synthesis of 1,2- and 1,3- amino-alcohols and their use in the enantioselective reduction of acetophenone and anti-acetophenone oxime methyl ether with borane
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New chiral amino-alcohols were enantioselectively synthesized using biotransformations as the key steps. They were used as ligand in the enantioselective borane reduction of acetophenone and of the corresponding anti oxime methyl ether.
- Didier, Eric,Loubinoux, Bernard,Ramos Tombo, Gerardo H.,Rihs, Grety
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p. 4941 - 4958
(2007/10/02)
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- Reduction of acyl enolates of alpha-substituted beta-keto esters by bakers' yeast.
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Enol esters of 2-substituted-3-oxoalkanoates of (Z)-configuration were reduced by bakers' yeast to chiral 2-substituted-3-hydroxyalkanoates. The syn-selectivities of this reaction increased compared with those of the reduction of the corresponding racemic
- Ohta,Kobayashi,Sugai
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p. 489 - 493
(2007/10/02)
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- Optically pure (S)-cyclopent-2-en-1-ol and (S)-3-methoxycylopentene
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Optically pure (S)-cyclopent-2-en-1-ol, D20 -137.9 deg (c 1.1, CHCl3), and (S)-3-methoxycyclopentene, D20 -116.9 deg (c 3.86, n-hexane), were prepared from ethyl (1R,2S)-2-hydroxycylopentanecarboxylate, which is readily available by yeast reduction of ethyl 2-oxocyclopentanecarboxylate.The optical purity of the alcohol was determined from its Mosher ester, and that of the ether by gas chromatography using a Ni-4-Pin column.
- Wahhab, Amal,Tavares, Donald F.,Rauk, Arvi
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p. 1559 - 1563
(2007/10/02)
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- ENHANCED OPTICAL PURITY OF 3-HYDROXYESTERS OBTAINED BY BAKER'S YEAST REDUCTION OF 3-KETOESTERS
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Fermenting Baker's yeast, enclosed in a dialysis tube, reduces efficiently 3-ketoesters added to the surrounding subtonic solution, to the corresponding 3-hydroxyesters in good yield (45-55percent) and enhanced optical purity (ee 96-97percent)
- Spiliotis, Vassilis,Papahatjis, Demetris,Ragoussis, Nikitas
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p. 1615 - 1616
(2007/10/02)
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- Baker's Yeast Mediated Bioreduction. A New Procedure Using Ethanol as an Energy Source
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A practical procedure using ethanol as an energy source was developed on the bakers's yeast mediated bioreduction of prochiral ketones.
- Kometani, Tadashi,Kitatsuji, Eitaro,Matsuno, Ryuichi
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p. 1465 - 1466
(2007/10/02)
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- Mono- and Dialkylation of Derivatives of (1R,2S)-2-Hydroxycyclopentanecarboxylic Acid and -cyclohexanecarboxylic Acid via Bicyclic Dioxanones: Selective Generation of Three Contiguous Stereogenic Centers on a Cyclohexane Ring
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Ethyl (1R,2S)-2-hydroxycyclopentanecarboxylate and -cyclohexanecarboxylate (1a and 2a, respectively) obtained in 40 and 70 percent yield by reduction of 3-oxocyclopentanecarboxylate and cyclohexanecarboxylate, respectively (Scheme 2), with non-fermenting
- Herradon, Bernardo,Seebach, Dieter
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p. 690 - 714
(2007/10/02)
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- Asymmetric Syntheses of (-)-Malyngolide and (-)-Frontalin by Utilizing Bakers' Yeast Reduction of S-Ethyl 2-Cyclopentanonecarboxylthioate
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Bakers' yeast reduction of S-ethyl 2-cyclopentanonecarboxylthioate affords optically pure S-ethyl (1R,2S)-2-hydroxycyclopentanecarboxylthioate which is stereoselectively converted into (-)-malyngolide and (-)-frontalin.
- Sato, Toshio,Maeno, Hajime,Noro, Tomohiro,Fujisawa, Tamotsu
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p. 1739 - 1742
(2007/10/02)
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- 148. Diastereo- und enantioselektive Reduktion von β-Ketoestern mit Cyclopentanon-, Cyclohexanon-, Piperidon- und Tetralon-Struktur durch nicht fermentierende Baecker-Hefe
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Under 'nonfermenting' conditions, i.e. in tap water, in the absence of nutrients, baker's yeast (25-380 g/g of substrate, aerobic) reduces β-keto esters such as those mentioned in the title with better selectivity than under the normally employed 'ferment
- Seebach, Dieter,Roggo, Silvio,Maetzke, Thomas,Braunschweiger, Hans,Cercus, Jacques,Krieger, Manfred
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p. 1605 - 1615
(2007/10/02)
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- DIASTEREOSELECTIVE AND ENANTIOSELECTIVE MICROBIAL REDUCTION OF CYCLIC alpha-ALKYL beta-KETOESTERS
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The reduction of racemic cyclopenta- and cyclohaxanone 2-carboxyesters by various yeast and mould strains was shown to produce different amounts of isomeric beta-hydroxyesters with predominant (1S) stereochemistry.With several strains, only one optically
- Buisson, Didier,Azerad, Robert
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p. 2631 - 2634
(2007/10/02)
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- An Examination of the Extent of Diastereofacial Selection in the Reactions of a Chiral Nitrile Oxide with Achiral Alkenes: a Route to β-Hydroxy Carboxylic Acids
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A new synthesis of optically active β-hydroxy carboxylic acids has been developed which is based on the (modest) diastereoselective addition of the chiral nitrile oxide (4) to 1,2-disubstituted alkenes.
- Kozikowski, Alan P.,Kitagawa, Yoshinori,Springer, James P.
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p. 1460 - 1462
(2007/10/02)
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