- Enantioselective cathodic reduction of some prochiral ketones in the presence of (-)-N,N′-dimethylquininium tetrafluoroborate at mercury cathode
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This work describes preparative scale enantioselective cathodic reduction of some prochiral ketones, viz. 3,4-dihydro-1(2H)-naphthaleneone, 2-octanone, 1-phenyl-2-propanone, E-3-octen-2-one, 1-octyn-3-one, 1-undecyn-3-one, 1-tetradecyn-3-one at mercury pool in N,N-dimethyl formamide (DMF)-2-propanol (9.5:0.5), using tetrabutylammonium tetrafluoroborate (TBA·BF4), as supporting electrolyte and (-)-N,N′-dimethylquininium tetrafluoroborate (DMQ·2BF4), as a enantioselective inductor. The products obtained were corresponding (S)-alcohols in 24-70% ee.
- Yadav, Ashok K.,Manju, Meera,Chhinpa, Pukh Raj
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- Novel chemoenzymatic strategy for the synthesis of enantiomerically pure secondary alcohols with sterically similar substituents
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A novel chemoenzymatic strategy for the synthesis of enantiomerically pure secondary alcohols with sterically similar substituents is described. The key step is the kinetic lipase-catalyzed resolution of racemic mixtures of substituted propargylic alcohols. The efficiency of this new approach was tested in the preparation of the corresponding enantiomers of 1,11-hexadecandiol derivatives ((R)-5 and (S)-5). Two strategies were tested. In the first one, the racemic intermediate 1-octyn-3-ol (1) was resolved enzymatically and then elongated with 1-bromo-9,11-dioxadodecane. Alternatively, the racemic 1 can be elongated to the corresponding racemic 17,19-dioxa-7-eicosyn-6-ol (3) first and then resolved biocatalytically. Twelve commercially available lipases were screened for the kinetic resolution of these intermediates. Among them, Candida antarctica lipase (CAL-B) and Humicola lanuginosa lipase (HLL) were the best biocatalysts for the resolution of 1 (S enantiomer 90% ee, E = 35), and 3 (R enantiomer 90% ee, E = 34), respectively.
- Abad, Jose-Luis,Soldevila, Carles,Camps, Francisco,Clapes, Pere
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- Palladium-catalyzed propargylic substitution with phosphorus nucleophiles: Efficient, stereoselective synthesis of allenylphosphonates and related compounds
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A new, efficient method is developed, based on a palladium(0)-catalyzed reaction of propargylic derivatives with various phosphorus nucleophiles, to produce allenylphosphonates and their analogues with defined stereochemistry in the allenic and the phosph
- Kalek, Marcin,Johansson, Tommy,Jezowska, Martina,Stawinski, Jacek
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- Practical preparation of both optically pure enantiomers of but-1-yn-3-ol, oct-1-yn-3-ol and 6-methylhept-2-yn-4-ol using biocartol as resolving agent
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A new facile preparation of optically pure secondary alkynols has been developed. This involves resolution of the corresponding racemic alcohols using biocartol as the resolving agent.
- Michelet,Besnier,Tanier,Touzin,Genet,Demoute
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- A Lipase Mediated Asymmetric Hydrolysis of 3-Acyloxy-1-octynes and 3-(E)-Acyloxy-1-octenes
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Optical resolution of 3-propionyloxy-1-trimethylsilyl-1-octyne or 3-(E)-propionyloxy-1-octene via lipase-mediated hydrolysis gave optically pure (S)-1-trimethylsilyl-1-octyn-3-ol and (R)-(E)-1-iodo-1-octen-3-ol, respectively, in which a reversal of enantio-selectivity for hydrolysis was observed between 3-propionyloxy-1-octyn and its 1-trimethylsilylated derivative, and the effect of the acyl groups on the enantio-discrimination was also investigated.
- Shimizu, Makoto,Kawanami, Hiroshi,Fujisawa, Tamotsu
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- Optically active propargylic and allylic alcohols with a difluoromethyl group at the terminal carbon
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Enantioselective esterification of α-substituted propargylic alcohols was found to proceed very smoothly in the presence of a catalytic amount of lipase (Nobozym 435) to yield the corresponding (R)-alcohols and (S)-acetates with high enantiomeric excess. Further, the preparation of optically active propargylic and allylic alcohols with a difluoromethyl group at the terminal carbon is described.
- Xiao, Ling,Kitazume, Tomoya
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- Highly Selective Manganese(I)/Lewis Acid Cocatalyzed Direct C?H Propargylation Using Bromoallenes
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A manganese(I)/Lewis acid cocatalyzed direct C?H propargylation with high selectivity has been developed. BPh3 was discovered to not only promote the reactivity, but also enhance the selectivity. Secondary, tertiary, and even quaternary carbon centers at the propargylic position could be directly constructed. Both internal and terminal alkynes are easily accessible. The chirality was successfully transferred from an axially chiral allene to central chirality. The reactivity of the manganese catalyst in this reaction was found to be unique among transition metal catalysts.
- Zhu, Can,Schwarz, Jonas Luca,Cembellín, Sara,Gre?ies, Steffen,Glorius, Frank
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supporting information
p. 437 - 441
(2018/02/21)
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- Ester Synthesis in Water: Mycobacterium smegmatis Acyl Transferase for Kinetic Resolutions
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The acyl transferase from Mycobacterium smegmatis (MsAcT) catalyses transesterification reactions in aqueous media because of its hydrophobic active site. Aliphatic cyanohydrin and alkyne esters can be synthesised in water with excellent and strikingly opposite enantioselectivity [(R);E>37 and (S);E>100, respectively]. When using this enzyme, the undesired hydrolysis of the acyl donor is an important factor to take into account. Finally, the choice of acyl donor can significantly influence the obtained enantiomeric excesses. (Figure presented.).
- de Leeuw, Nicolas,Torrelo, Guzman,Bisterfeld, Carolin,Resch, Verena,Mestrom, Luuk,Straulino, Emanuele,van der Weel, Laura,Hanefeld, Ulf
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p. 242 - 249
(2017/11/16)
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- Asymmetric Total Syntheses of Two Possible Diastereomers of Gliomasolide e and Its Structural Elucidation
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The first total syntheses of two possible diastereomers of gliomasolide E, a 14-membered macrolides isolated from the marine sponge Phakellia fusca Thiele, which was collected from the South China Sea, is reported. Highlights of the synthesis include macrolactonization through intramolecular Horner-Wadsworth-Emmons olefination, Yamaguchi-Hirao alkynylation, and base-induced elimination reactions for propargyl alcohol synthesis as the key reactions. Detailed comparison of their 1H and 13C NMR (1D and 2D NMR data) and specific rotation with those of the natural product revealed that the absolute stereochemistry of gliomasolide E should be (2E,5R,7R,9R,13R).
- Reddy, Ramidi Gopal,Venkateshwarlu, Ravula,Ramakrishna, Kallaganti V. S.,Yadav, Jhillu S.,Mohapatra, Debendra K.
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p. 1053 - 1063
(2018/06/18)
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- A general asymmetric synthesis of (R)-Matsutakeol and flavored analogs
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An efficient and practical synthetic route toward chiral matsutakeol and analogs was developed by asymmetric addition of terminal alkyne to aldehydes. (R)-matsutakeol and other flavored substances were feasibly synthesized from various alkylaldehydes in high yield (up to 49.5%, in three steps) and excellent enantiomeric excess (up to >99%). The protocols may serve as an alternative asymmetric synthetic method for active small-molecule library of natural fatty acid metabolites and analogs. These chiral allyl alcohols are prepared for food analysis and screening insect attractants.
- Liu, Jia,Li, Honglian,Zheng, Chao,Lu, Shichao,Guo, Xianru,Yin, Xinming,Na, Risong,Yu, Bin,Wang, Min
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- Coupling biocatalysis and click chemistry: One-pot two-step convergent synthesis of enantioenriched 1,2,3-triazole-derived diols
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A fully convergent one-pot two-step synthesis of different chiral 1,2,3-triazole-derived diols in high yields and excellent enantio- and diastereoselectivities has been achieved under very mild conditions in aqueous medium by combining a single alcohol dehydrogenase (ADH) with a Cu-catalysed 'click' reaction. The Royal Society of Chemistry 2013.
- Cuetos, Aníbal,Bisogno, Fabricio R.,Lavandera, Iván,Gotor, Vicente
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supporting information
p. 2625 - 2627
(2013/04/23)
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- One-pot deracemization of sec-alcohols: Enantioconvergent enzymatic hydrolysis of alkyl sulfates using stereocomplementary sulfatases
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Hand in hand: The title transformation was achieved using a pair of sulfatases acting through inversion and retention of configuration on opposite substrate enantiomers. Using Pseudomonas aeruginosa arylsulfatase PAS with alkylsulfatase PISA1 in one-pot l
- Schober, Markus,Toesch, Michael,Knaus, Tanja,Strohmeier, Gernot A.,Van Loo, Bert,Fuchs, Michael,Hollfelder, Florian,Macheroux, Peter,Faber, Kurt
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p. 3277 - 3279
(2013/04/23)
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- A stereoselective inverting sec -alkylsulfatase for the deracemization of sec -alcohols
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A metallo-β-lactamase-type alkylsulfatase was found to catalyze the enantioselective hydrolysis of sec-alkylsulfates with strict inversion of configuration. This catalytic event, which does not have an analog in chemocatalysis, yields homochiral (S)-configurated alcohols and nonreacted sulfate esters. The latter could be converted into (S)-sec-alcohols as the sole product in up to >99% ee via a chemoenzymatic deracemization protocol on a preparative scale.
- Schober, Markus,Gadler, Petra,Knaus, Tanja,Kayer, Heidemarie,Birner-Gruenberger, Ruth,Guelly, Christian,MacHeroux, Peter,Wagner, Ulrike,Faber, Kurt
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supporting information; experimental part
p. 4296 - 4299
(2011/10/08)
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- Novel, stereoselective and stereospecific synthesis of allenylphosphonates and related compounds via palladium-catalyzed propargylic substitution
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We have developed a novel method for the synthesis of allenylphosphonates and related compounds based on a palladium(0)-catalyzed reaction of propargylic derivatives with H-phosphonate, H-phosphonothioate, H-phosphonoselenoate, and H-phosphinate esters. The reaction is stereoselective and stereospecific, and provides a convenient entry to a vast array of allenylphosphonates and their analogues with diverse substitution patterns in the allenic moiety and at the phosphorus center. Some mechanistic aspects of this new reaction were also investigated. Copyright
- Kalek, Marcin,Stawinski, Jacek
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supporting information; experimental part
p. 1741 - 1755
(2011/09/15)
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- Total synthesis of halicholactone and neohalicholactone
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New total syntheses of the marine oxylipins halicholactone and neohalicholactone are presented. The key building blocks were synthesized utilizing chemoenzymatic methods.
- Bischop, Martina,Doum, Verena,Nordschild Nee Rieche, Anja C. M.,Pietruszka, Joerg,Sandkuhl, Diana
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experimental part
p. 527 - 537
(2010/06/16)
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- Toward preparative resolution of chiral alcohols by an organic chemical method
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Asymmetric alcohols were resolved as 1-α-O-alkyl-2,3-unsaturated hexosides. After separation of diastereoisomers, the auxiliary and the enantiomeric alcohol were recovered by transglycosidation. Potential applications include resolution of labile secondary and tertiary alcohols, difficult by existing techniques, and enhancement of ees of chiral alcohols produced enzymatically or by synthetic catalytic methods. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010.
- Malic, Nino,Moorhoff, Cornelis,Sage, Valerie,Saylik, Dilek,Teoh, Euneace,Scott, Janet L.,Strauss, Christopher R.
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supporting information; experimental part
p. 398 - 402
(2010/06/14)
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- Palladium-catalyzed intramolecular hydroamination of allenes coupled to aerobic alcohol oxidation
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The palladium-catalyzed intramolecular hydroamination of allenes was investigated under a dioxygen atmosphere where bathocuproine was used as the ligand. The study tested the reaction of N-(y-allenyl)tosylamide with the proposed Pd-hydride species formed
- Qiu, Shuifa,Wei, Yunyang,Liu, Guosheng
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supporting information; experimental part
p. 2751 - 2754
(2009/12/04)
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- Kinetic resolution of propargylic alcohols catalyzed by benzotetramisole
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(Chemical Equation Presented) Kinetic resolution of variously substituted secondary propargylic alcohols catalyzed by benzotetramisole (BTM) proceeds with selectivity factors up to 32, the highest ever achieved with nonenzymatic catalysts for this class o
- Birman, Vladimir B.,Guo, Lei
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p. 4859 - 4861
(2007/10/03)
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- Synthesis and use of stereospecifically deuterated analogues of palmitic acid to investigate the stereochemical course of the Δ11 desaturase of the processionary moth
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Thaumetopoea pityocampa pheromone glands contain desaturases that, after several sequential reactions from palmitic acid, catalyze the formation of a unique enyne fatty acid, which is the immediate sex pheromone precursor. In this article, we describe the synthesis of different stereospecifically deuterium-labeled and isotopically tagged palmitic acid probes needed to decipher the stereochemical course of the T. pityocampa Δ11 desaturase. The synthesis of probes has been carried out by a chemoenzymatic route, in which the key step is the kinetic lipase-catalyzed resolution of racemic mixtures of secondary propargyl alcohols. The presence of the acetylenic bond simplifies the absolute configuration determination of the resolved alcohols. Moreover, it allows the introduction of the isotopic tag by deuteration. By use of the probes thus prepared, experimental evidence is presented that the Δ11 desaturase of T. pityocampa transforms palmitic acid into (Z)-11-hexadecenoic acid by removal of the pro-(R)-hydrogen atoms from both C11 and C12.
- Abad, Jose-Luis,Villorbina, Gemma,Fabrias, Gemma,Camps, Francisco
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p. 7108 - 7113
(2007/10/03)
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- The effect of catechin derivatives on the enantioselectivity of lipase-catalyzed hydrolyses of alkynol benzoate esters
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Polyphenols, such as (+)-catechin and pyrogallol could be used to enhance stereochemical control in the lipase-catalyzed hydrolysis of alkynol benzoate esters, leading to increased enantioselectivities in the kinetic resolution of alkynols with lipase Amano AH.
- Nakamura, Kaoru,Takenaka, Keishi
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p. 415 - 422
(2007/10/03)
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- Preparation of optically pure propargylic and allylic alcohols from 2-(trimethylsilyl)vinyl sulfoxides as a chiral ethynyl anion synthon: Computational studies on elimination reaction of 2-(trimethylsilyl)vinyl sulfoxides
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The reaction of the (α-carbanion derived from (trimethylsilyl)vinyl sulfoxides with aldehydes afforded a diastereomeric mixture of the products. Each diastereomer was subjected to specific elimination reactions to give optically pure propargylic, trimethylsilylated propargylic, and allylic alcohols. Acceleration of the sulfenic acid-elimination from the β-silylvinyl sulfoxide was demonstrated by the ab initio calculation to be ascribed mainly to the β-effect of the silyl group.
- Nakamura, Shuichi,Kusuda, Shinya,Kawamura, Kiyoshi,Toru, Takeshi
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p. 640 - 647
(2007/10/03)
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- Enantioselective synthesis of both enantiomers of various propargylic alcohols by use of two oxidoreductases
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The oxidoreductases Lactobacillus brevis alcohol dehydrogenase (LBADH) and Candida parapsilosis carbonyl reductase (CPCR) are suitable catalysts for the reduction of ketones to afford enantiopure sec. alcohols. A broad variety of alkynones (1, 3, and 5) are accepted as substrates and the corresponding propargylic alcohols (2, 4, and 6) are obtained in good yield and excellent enantiomeric excess. By changing the steric demand of the substituents the ee values can be adjusted and even the configurations of the products can be altered.
- Schubert, Thomas,Hummel, Werner,Kula, Maria-Regina,Mueller, Michael
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p. 4181 - 4187
(2007/10/03)
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- Total synthesis of aspirin-triggered 15-epi-lipoxin A4
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The total synthesis of aspirin-triggered 15-epi-LXA4 has been achieved using a chiral pool strategy for the C1-C12 fragment starting from 2-deoxy-D-ribose. Sharpless catalytic AE generated the C15 chiral center with >98% ee. The stereospecific (Z)-reduction of the conjugated trienyne to the tetraene was achieved with Zn(Cu/Ag) in aq. CH3OH at rt.
- Rodríguez, Ana R,Spur, Bernd W
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p. 6057 - 6060
(2007/10/03)
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- Facile, asymmetric addition of acetylene to aldehydes: In situ generation of reactive zinc acetylide
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This study documents a process in which acetylene is employed directly in nucleophilic additions to aldehydes to give adducts in high levels of enantiomeric induction, up to 98% ee. To the best of our knowledge, this represents the first time in which acetylene itself has been utilized in such ligand-controlled enantioselective additions.
- Sasaki, Hiroshi,Boyall, Dean,Carreira, Erick M.
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p. 964 - 971
(2007/10/03)
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- Cuprous chloride accelerated Stille reactions. A general and effective coupling system for sterically congested substrates and for enantioselective synthesis
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A major limitation of Stille coupling reactions arises from steric screening, especially in the vinylstannane component. For example, with 1- substituted vinylstannanes and aryl perfluoroalkanesulfonates or halides negligible or low yields are generally observed, due to very slow reaction rates and competing cine substitution. This problem has been overcome in the present work through the discovery and application of cuprous chloride as an accelerant for coupling. Thus, using a protocol for coupling that involves the system Pd(PPh3)4/CuCl/LiCl under anaerobic conditions in dimethyl sulfoxide solution at 60 °C, a wide variety of Stille coupling reactions which otherwise fail can be effected in excellent yield (Table 1). The process has been applied to the enantioselective synthesis of the chiral 1- (arylethyl)alkylcarbinol 26, a model for the natural product nicandrenone. The acceleration of Stille coupling by cuprous chloride can be explained by the intervention of a vinylstannane → vinylcopper(I) transmetalation step and a subsequent accelerated coupling of ArPdX with the vinylcopper(I) intermediate.
- Han, Xiaojun,Stoltz, Brian M.,Corey
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p. 7600 - 7605
(2007/10/03)
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- Reduction of Ketones with LiAlH4 Complexes of α,α,α′,α′-Tetraaryl-1,3-dioxolane-4,5- dimethanols (TADDOLs): A Combination of Enantioselective Reduction and Clathrate Formation with a Discussion of LAH Reagents Bearing C2-Symmetrical Ligands
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A complex prepared from one equivalent each of LiAlH4, EtOH and a TADDOL (α,α,α′,α′-tetraaryl-1,3-dioxolane-4,5- dimethanol) reduces aryl alkyl ketones to sec. alcohols with enantiomer ratios (er) up to 96:4. The chiral LAH derivative is used in two-fold excess in THF solution and at dry ice temperatures. The ability of TADDOLs to form clathrates diastereoselectively can be exploited to increase the er of the initially formed alcohols by a simple modification of the work-up procedure and hence, products of very high enantiopurity (er 99:1) can be isolated. When (R,R)-TADDOLs (from (R,R)-tartrate) are applied in the reaction, the 1-aryl-alkanols formed preferentially have (S) configuration, as for the products obtained with the corresponding (P)-BINOL and (P)-BIPHENOL derivatives. A common mechanistic model is discussed.
- Seebach, Dieter,Beck, Albert K.,Dahinden, Robert,Hoffmann, Matthias,Kuehnle, Florian N. M.
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p. 459 - 484
(2007/10/03)
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- Convenient Preparation of Optically Pure Propargylic Alcohols Using 2-(Trimethylsilyl)vinyl Sulfoxide As A Novel Chiral Synthon
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Both enentiomers of optically pure propargylic alcohols are conveniently prepared by the reaction of α-vinyl anion of 2-(trimethylsilyl)vinyl p-tolyl sulfoxide with aldehydes and subsequent either desilylsulfination or thermal elimination of the sulfinyl group.
- Kusuda, Shinya,Kawamura, Kiyoshi,Ueno, Yoshio,Toru, Takeshi
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p. 6587 - 6590
(2007/10/02)
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- A practical access to optically pure (S)-1-octyn-3-ol
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A highly efficient resolution of (±)-1-octyn-3-ol through recrystallization of the diastereomeric esters has been achieved by using N-(p-toluenesulfonyl)-(S)-phenylalanyl chloride as resolving reagent. The method provides a facile and economical entry to
- Hashimoto,Kase,Suzuki,Yanagiya,Ikegami
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p. 833 - 839
(2007/10/02)
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- PRACTICAL METHOD FOR SYNTHESIS OF OPTICALLY PURE PROPARGYLIC ALCOHOLS
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Highly efficient practical method for synthesis of optically pure propargylic alcohols is described which involves the synthesis of chiral γ-iodo allylic alcohols by the Sharpless kinetic resolution of secondary γ-hetero substituted allylic alcohols and their 1,2-dehydrohalogenation reaction.
- Ito, Takayori,Okamoto, Sentaro,Sato, Fumie
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p. 7083 - 7086
(2007/10/02)
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- Asymmetric Construction of Optically Active 3-Hydroxyalkyne Functionalities
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An efficient method for the construction of optically active 3-hydroxyalkyne functionalities has been developed using optically active α,β-epoxy alcohols readily accessible from non-chiral allyl alcohol precursors.
- Takano, Seiichi,Samuzi, Kiyohiro,Sugihara, Takumichi,Ogasawara, Kunio
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p. 1344 - 1345
(2007/10/02)
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- Coupling Reactions of 1-Tributylstannyl-1-octen-3-ol Catalyzed by Palladium: The Synthesis of PGB1 and Coriolic Acid
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The palladium catalyzed coupling of (S)-E-1-tributylstannyl-1-octen-3-ol (3) with 2-(6-carbethoxyhexyl)-3-iodo-2-cyclopenten-1-one gave a 70percent yield of the (S)-ethyl ester of PGB1.Coriolic acid was synthesized in 75percent yield by coupling 3 with Z-10-iododecenoic acid, demonstrating the tolerance of this coupling reaction to the carboxylic acid function.
- Stille, J.K.,Sweet, Mark P.
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p. 3645 - 3648
(2007/10/02)
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- REDUCTION DE DERIVES D'ALCOOLS PROPARGYLIQUES CATALYSEE PAR UN COMPLEXE DE PALLADIUM ZEROVALENT
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Catalysis by tetrakis(triphenylphosphine)palladium of the reaction of hydride donnors with secondary propargylic bromides, mesylates and phosphates increases markedly the amount of allene produced.The best results in that direction are obtained with mesylates and phosphates by using lithium triethylborohydride.The reaction then occurs with an ANTI introduction of the hydride with respect to the leaving group.A mechanism is proposed which explains the influence of the various parameters of the reaction.
- Colas, Yann,Cazes, Bernard,Gore, Jacques
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p. 165 - 173
(2007/10/02)
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- A HIGHLY EFFICIENT SYNTHESIS OF γ-HALO ALLYLIC ALCOHOLS AND PROPARGYLIC ALCOHOLS WITH OPTICAL PURITY. PRACTICAL METHOD FOR SYNTHESIS OF THE PROSTAGLANDIN ω-CHAIN.
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Kinetic resolution of γ-trimethylsilyl allylic alcohols 5 by the Sharpless process combined with the reactivity of epoxysilyl or vinylsilyl compounds affords a highly efficient method for preparation of optically pure γ-halo secondary allylic alcohols of type 1-4 and propargylic alcohols 14, thus providing a practical route to the prostaglandin ω-chain.
- Okamoto, Sentaro,Shimazaki, Toshiyuki,Kobayashi, Yuichi,Sato, Fumie
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p. 2033 - 2036
(2007/10/02)
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- ASYMMETRIC REDUCTIONS OF PROPARGYL KETONESAN EFFECTIVE APPROACH TO THE SYNTHESIS OF OPTICALLY-ACTIVE COMPOUNDS
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Propargyl ketones are readily reduced by the asymmetric reducing agent B-3-pinanyl-9-borabicyclo-nonane (Alpine-borane).The reagent prepared from (+)-α-pinene and 9-BBN provides the R enantiomer while the S enantiomer can be obtained from (-)-α-pinene.Alternatively the S enantiomer ca be prepared from the reagent derived from 9-BBn and the benzyl ether of nopol (6,6-dimethyl-bicyclohept-2-ene-2-ethanol).The limiting factor in obtaining high enantiomeric induction is often the enantiomeric purity of the α-pinene.With 100percent enantiomerically pure α-pinene, propargyl alcohols of essentially 100percent ee can be obtained.A predictive rationalization of the transition state leading to this remarkable selection is presented.The acetylene unit of the propargyl alcohol provides a convenient handle for transformations to other useful, optically-active products.The use of propargyl alcohols for the synthesis of optically-active α- and β-substituted γ-lactones, and δ-lactones is illustrated.
- Midland, M. Mark,Tramontano, Alfonso,Kazubski, Aleksander,Graham, Richard S.,Tsai, David J. S.,Cardin, Daniel B.
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p. 1371 - 1380
(2007/10/02)
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- Synthetic Applications of the Enantioselective Reduction by Binaphthol-Modified Lithium Aluminum Hydride Reagents
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The reduction of prochiral carbonyl substrates with the chiral binaphthol-modified lithium aluminum hydride reagents provides an effective means for preparing alcoholic products of high optical purity.The reaction is applicable to a variety of structurally diverse unsaturated carbonyl compounds such as aromatic ketones, acetylenic ketones, olefinic ketones and aldehydes, etc.Either of the antipodes is obtainable in a predictable manner by choosing the handedness of the auxiliary binaphthol ligand.The utility is exemplified by the efficiently stereocontrolled synthesis of prostaglandin intermediates, some insect pheromones, chiral primary terpenic alcohols, optically active styrene oxide, etc.
- Noyori, R.,Tomino, I.,Yamada, M.,Nishizawa, M.
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p. 6717 - 6725
(2007/10/02)
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- Reduction of α,β-Acetylenic Ketones to (S)-Propargyl Alcohols of High Enantiomeric Purity
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(S)-Propargyl alcohols may be obtained in 86-96percent enantiomeric purity by asymmetric reduction of α,β-acetylenic ketones with the 9-borabicyclononane (9-BBN) adduct of nopol benzyl ether.
- Midland, Mark M.,Kazubski, Aleksander
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p. 2814 - 2816
(2007/10/02)
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- Enzymic Resolution of (+/-)-Acyclic Alcohols via Asymmetric Hydrolysis of Corresponding Acetates by Microorganisms
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Asymmetric hydrolysis of (+/-)-1-pentyl-2-propynyl and 1-pentyl-2-propenyl acetates by selected microorganisms produced chiral 1-octyn-3-ol and 1-octen-3-ol, respectively, with high optical purities and acetates of their antipodes.Enantioselectivity of microbial hydrolysis changed with the microorganisms used.Also, (+/-)-1-ethylhexyl acetate was asymmetrically hydrolyzed by microorganisms to give (S)-3-octanol and (R)-1-ethylhexyl acetate of relatively low optical purity and hydrolytic ratio, compared with those of (+/-)-1-pentyl-2-propynyl acetate.
- Oritani, Takayuki,Yamashita, Kyohei
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p. 2407 - 2412
(2007/10/02)
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