- CHIRAL SYNTHESIS OF (2S,3S,7S)-3,7-DIMETHYLPENTADECAN-2-YL ACETATE AND PROPIONATE, POTENTIAL SEX PHEROMONE COMPONENTS OF THE PINE SAW-FLY NEODIPRION SERTIFER (GEOFF.)
-
A synthesis of (2S,3S,7S)-3,7-dimethylpentadecan-2-yl acetate (2) and propionate (3) is described. (2S)-2-Methyldecan-1-yl lithium (5) was reacted with (3S,4S)-3,4-dimethyl-γ-butyrolactone (6) to yield the ketoalcohol 19 which upon Huang-Minlon reduction furnished (2S,3S,7S)-3,7-dimethylpentadecan-2-ol (1).Acylations gave the esters 2 and 3.The (2S)-2-methyldecan-1-yl lithium was obtained via asymmetric synthesis.The chiral lactone 6 was obtained from (2S,3S)-trans-2,3-epoxybutane and dimethylmalonate.
- Bystroem, Styrbjoern,Hoegberg, Hans-Erik,Norin, Torbjoern
-
-
Read Online
- Effect of Methyl Substitution on Conformation and Molecular Arrangement of BEDT-TTF Derivatives in the Crystalline Environment
-
Two methylated bis(ethylenedithio)tetrathiafulvalene (ET) derivatives, Me2ET and Me4ET were stereoselectively synthesized to examine the effect of methylation on conformations of dihydrodithiin rings and molecular arrangements in the crystalline state.Since the donating ability of Me2ET and Me4ET are similar to that of ET, the methylated ET derivatives are considered to be appropriate to investigate the "lattice pressure" effect on ET radical salts by changing the volume of donor molecules.The upper limit of an activation energy for the ring inversion of the dimethylated dihydrodithiin in solution was estimated to be 32 kJ mol-1 by 13C NMR spectroscopy.The X-ray structure analyses revealed that orientations of methyl groups are fixed to axial in Me2ET and to equatorial in Me4ET, accompanied by the change of molecular stacking.The "volume of a methyl group" was evaluated by comparing the molecular volumes of Me2ET and Me4ET with that of ET, and the effective volume for the axial methyl group turns out to be 15percent larger than that of the equatorial.The solid state 13C NMR (CP/MAS) spectra of ET and its derivatives showed that the chemical shifts of resonance lines reflect the conformations of dihydrodithiin rings in crystals.
- Matsumiya, Shigeki,Izuoka, Akira,Sugawara, Tadashi,Taruishi, Tomohiro,Kawada, Yuzo
-
-
Read Online
- Properties of diacetyl (acetoin) reductase from Bacillus stearothermophilus
-
The cells of Bacillus stearothermophilus contain an NADH-dependent diacetyl (acetoin) reductase. The enzyme was easily purified to homogeneity, partially characterised, and found to be composed of two subunits with the same molecular weight. In the presence of NADH, it catalyses the stereospecific reduction of diacetyl first to (3S)-acetoin and then to (2S,3S)-butanediol; in the presence of NAD+, it catalyses the oxidation of (2S,3S)- and meso-butanediol, respectively to (3S)-acetoin and to (3R)-acetoin, but is unable to oxidise these compounds to diacetyl. The enzyme is also able to catalyse redox reactions involving some endo-bicyclic octen- and heptenols and the related ketones, and its use is suggested also for the recycling of NAD+ and NADH in enzymatic redox reactions useful in organic syntheses.
- Giovannini, P. Paolo,Medici, Alessandro,Bergamini, Carlo M.,Rippa, Mario
-
-
Read Online
- An improved synthesis of chiral diols via the asymmetric catalytic hydrogenation of prochiral diones
-
The rates of the asymmetric hydrogenation of prochiral diketones catalyzed by Ru(BINAP) catalysts were substantially accelerated in the presence of small amounts of a strong acid.
- Fan, Qing-Hua,Yeung, Chi-Hung,Chan, Albert S. C.
-
-
Read Online
- Application of robust ketoreductase from Hansenula polymorpha for the reduction of carbonyl compounds
-
Enzyme-catalysed asymmetric reduction of ketones is an attractive tool for the production of chiral building blocks or precursors for the synthesis of bioactive compounds. Expression of robust ketoreductase (KRED) from Hansenula polymorpha was upscaled and applied for the asymmetric reduction of 31 prochiral carbonyl compounds (aliphatic and aromatic ketones, diketones and β-keto esters) to the corresponding optically pure hydroxy compounds. Biotransformations were performed with the purified recombinant KRED together with NADP+ recycling glucose dehydrogenase (GDH, Bacillus megaterium), both overexpressed in Escherichia coli BL21(DE3). Maximum activity of KRED for biotransformation of ethyl-2-methylacetoacetate achieved by the high cell density cultivation was 2499.7 ± 234 U g–1DCW and 8.47 ± 0.40 U·mg–1E, respectively. The KRED from Hansenula polymorpha is a very versatile enzyme with broad substrate specificity and high activity towards carbonyl substrates with various structural features. Among the 36 carbonyl substrates screened in this study, the KRED showed activity with 31, with high enantioselectivity in most cases. With several ketones, the Hansenula polymorpha KRED catalysed preferentially the formation of the (R)-secondary alcohols, which is highly valued.
- Petrovi?ová, Tatiana,Gyuranová, Dominika,Pl?, Michal,Myrtollari, Kamela,Smonou, Ioulia,Rebro?, Martin
-
-
- Highly efficient and recyclable chiral Pt nanoparticle catalyst for enantioselective hydrogenation of activated ketones
-
Thermoregulated phase-separable chiral Pt nanoparticle catalyst exhibited excellent ee (>99%) in the enantioselective hydrogenation of activated ketones for preparing chiral α-hydroxy acetals and chiral 1,2-diols. More importantly, the chiral catalyst could be easily separated by phase separation and directly reused in the next cycle without any loss in catalytic activity and enantioselectivity, even in the gram-scale reaction. The leaching of Pt was under the detection limit of the instrument.
- Xue, Xiuru,Chen, Pu,Xu, Peng,Wang, Yanhua
-
-
- MICRO-ORGANISM FOR THE PRODUCTION OF STEREO-SPECIFIC S, S-2,3-BUTANEDIOL
-
The invention relates to a genetically modified lactic acid bacterium capable of producing (S,S)-2,3-butanediol stereo specifically from glucose under aerobic conditions. Additionally the invention relates to a method for producing (S,S)-2,3-butanediol and L-acetoin using the genetically modified lactic acid bacterium, under aerobic conditions in the presence of a source of iron-containing porphyrin or a source of metal ions (Fe3+/Fe2+). The lactic acid bacterium is genetically modified to express heterologous genes encoding enzymes catalysing the stereo-specific synthesis of (S,S)-2,3-butanediol; and additionally a number of genes are deleted in order to maximise the production of (S,S)-2,3-butanediol as compared to other products of oxidative fermentation.
- -
-
Page/Page column 27-28
(2016/07/05)
-
- Biocatalytic production of alpha-hydroxy ketones and vicinal diols by yeast and human aldo-keto reductases
-
The α-hydroxy ketones are used as building blocks for compounds of pharmaceutical interest (such as antidepressants, HIV-protease inhibitors and antitumorals). They can be obtained by the action of enzymes or whole cells on selected substrates, such as diketones. We have studied the enantiospecificities of several fungal (AKR3C1, AKR5F and AKR5G) and human (AKR1B1 and AKR1B10) aldo-keto reductases in the production of α-hydroxy ketones and diols from vicinal diketones. The reactions have been carried out with pure enzymes and with an NADPH-regenerating system consisting of glucose-6-phosphate and glucose-6-phosphate dehydrogenase. To ascertain the regio and stereoselectivity of the reduction reactions catalyzed by the AKRs, we have separated and characterized the reaction products by means of a gas chromatograph equipped with a chiral column and coupled to a mass spectrometer as a detector. According to the regioselectivity and stereoselectivity, the AKRs studied can be divided in two groups: one of them showed preference for the reduction of the proximal keto group, resulting in the S-enantiomer of the corresponding α-hydroxy ketones. The other group favored the reduction of the distal keto group and yielded the corresponding R-enantiomer. Three of the AKRs used (AKR1B1, AKR1B10 and AKR3C1) could produce 2,3-butanediol from acetoin. We have explored the structure/function relationships in the reactivity between several yeast and human AKRs and various diketones and acetoin. In addition, we have demonstrated the utility of these AKRs in the synthesis of selected α-hydroxy ketones and diols.
- Calam, Eduard,Porté, Sergio,Fernández, M. Rosario,Farrés, Jaume,Parés, Xavier,Biosca, Josep A.
-
p. 195 - 203
(2013/05/08)
-
- Manipulating the Expression Rate and Enantioselectivity of an Epoxide Hydrolase by Using Directed Evolution
-
We describe here a strategy to improve the expression efficiency and enantioselectivity of Aspergillus niger epoxide hydrolase (ANEH) by directed evolution. Based on a blue-colony screening system using the LacZα (β-galactosidase α peptide) complementation solubility reporter, several ANEH variants out of 15000 transformants from a random-mutagenesis library were identified that show improved recombinant expression in E. coli. Among them, Pro221Ser was subsequently used as a template for iterative saturation mutagenesis (ISM) at sites around the ANEH binding pocket. Following four rounds of ISM, a highly enantioselective mutant was identified that catalyzes the hydrolytic kinetic resolution of racemic glycidyl phenyl ether with a selectivity factor of E=160 in favor of the (S)-diol compared to WT ANEH characterized by E=4.6. Expression of this mutant is 50 times higher than that of WT ANEH. It also serves as an excellent stereoselective catalyst in the hydrolytic kinetic resolution and desymmetrization of several other structurally diverse epoxides. Copyright
- Reetz, Manfred T.,Zheng, Huabao
-
experimental part
p. 1529 - 1535
(2012/05/31)
-
- Manipulating the stereoselectivity of limonene epoxide hydrolase by directed evolution based on iterative saturation mutagenesis
-
Limonene epoxide hydrolase from Rhodococcus erythropolis DCL 14 (LEH) is known to be an exceptional epoxide hydrolase (EH) because it has an unusual secondary structure and catalyzes the hydrolysis of epoxides by a rare one-step mechanism in contrast to the usual two-step sequence. From a synthetic organic viewpoint it is unfortunate that LEH shows acceptable stereoselectivity essentially only in the hydrolysis of the natural substrate limonene epoxide, which means that this EH cannot be exploited as a catalyst in asymmetric transformations of other substrates. In the present study, directed evolution using iterative saturation mutagenesis (ISM) has been tested as a means to engineer LEH mutants showing broad substrate scope with high stereoselectivity. By grouping individual residues aligning the binding pocket correctly into randomization sites and performing saturation mutagenesis iteratively using a reduced amino acid alphabet, mutants were obtained which catalyze the desymmetrization of cyclopentene-oxide with stereoselective formation of either the (R,R)- or the (S,S)-diol on an optional basis. The mutants prove to be excellent catalysts for the desymmetrization of other meso-epoxides and for the hydrolytic kinetic resolution of racemic substrates, without performing new mutagenesis experiments. Since less than 5000 tranformants had to be screened for achieving these results, this study contributes to the generalization of ISM as a fast and reliable method for protein engineering. In order to explain some of the stereoselective consequences of the observed mutations, a simple model based on molecular dynamics simulations has been proposed.
- Zheng, Huabao,Reetz, Manfred T.
-
supporting information; experimental part
p. 15744 - 15751
(2011/02/21)
-
- Rhodotorula minuta-mediated bioreduction of 1,2-diketones
-
The reduction of cyclic and acyclic 1,2-diketones was investigated by employing whole cells of the yeast Rhodotorula minuta as biocatalyst. The reactions showed a variable degree of regio- and enantioselectivity depending on the nature of the substrate. In the case of cyclic diketones, the reduction afforded a mixture of diastereomeric diols only. The reduction of acyclic diketones allowed production of both the hydroxy ketone and the diol, in a two-step reaction. The first step was highly regio- and stereoselective, affording the hydroxy ketone of (S)-configuration with high enantiomeric excess. After longer reaction times the corresponding (S,S)-diols were obtained in high yield and diastereomeric excess.
- Monsalve, Leandro N.,Cerrutti, Patricia,Galvagno, Miguel A.,Baldessari, Alicia
-
experimental part
p. 137 - 143
(2011/11/12)
-
- PROCESS FOR PRODUCTION OF OPTICALLY ACTIVE ALCOHOLS
-
A ruthenium complex RuCl[(S,S)-Tsdpen](p-cymene) represented by a formula below and a ketone compound are placed in a polar solvent, and the resulting mixture is mixed under pressurized hydrogen to hydrogenate the ketone compound and to thereby produce an optically active alcohol:
- -
-
Page/Page column 13
(2008/06/13)
-
- Direct proline-catalyzed asymmetric α-aminoxylation of aldehydes and ketones
-
The direct proline-catalyzed asymmetric α-aminoxylation of aldehydes and ketones has been developed using nitrosobenzene as an oxygen source, affording α-anilinoxy-aldehydes and -ketones with excellent enantioselectivity. Reaction conditions have been optimized, and low temperature (-20 °C) was found to be a key for the successful α-aminoxylation of aldehydes, while slow addition of nitrosobenzene is essential for that of ketones. The scope of the reaction is presented.
- Hayashi, Yujiro,Yamaguchi, Junichiro,Sumiya, Tatsunobu,Hibino, Kazuhiro,Shoji, Mitsuru
-
p. 5966 - 5973
(2007/10/03)
-
- DERMATOLOGICAL COMPOSITIONS AND METHODS
-
Disclosed are methods and compositions for regulating the melanin content of mammalian melanocytes; regulating pigmentation in mammalian skin, hair, wool or fur; treating or preventing various skin and proliferative disorders; by administration of various compounds, including alcohols, diols and/or triols and their analogues.
- -
-
-
- Chemoenzymatic preparation of (2S,3S)- and (2R,3R)-2,3-butanediols and their esters from mixtures of d,l- and meso-diols
-
An efficient method of preparing the pure enantiomers of 2,3-butanediol from commercially available mixtures of the d,l- and meso-isomers was developed. It furnished (2S,3S)-2,3-butanediol with >99% e.e. and a >99.5/0.5 diastereomeric ratio and (2R,3R)-2,3-butanediol in 95% e.e. and >95/5 diastereomeric ratio.
- Liu, Rong,Hoegberg, Hans-Erik
-
p. 771 - 778
(2007/10/03)
-
- Treatment of neurodegenerative diseases
-
Disclosed are methods for increasing the differentiation of mammalian neuronal cells for purposes of treating neurodegenerative diseases or nerve damage by administration of various compounds including alcohols, diols and/or triols and their analogues.
- -
-
-
- Asymmetric hydrosilylation of ketones using trans-chelating chiral peralkylbisphosphine ligands bearing primary alkyl substituents on phosphorus atoms
-
Asymmetric hydrosilylation of simple ketones with diphenylsilane proceeded at -40 °C in the presence of a rhodium complex (0.001 - 0.01 molar amount) coordinated with a trans-chelating chiral bisphosphine ligand bearing linear alkyl substituents on the phosphorus atoms, (R,R)-(S,S)-Et-, Pr-, or BuTRAP, giving the corresponding optically active (S)- secondary alcohols with up to 97% ee. The asymmetric hydrosilylation using TRAP ligands with bulkier P-substituents resulted in much lower enantioselectivities. The EtTRAP-rhodium catalyst was also effective for asymmetric hydrosilylation of keto esters with a coordination site for a rhodium atom (up to 98% ee). Optically active symmetrical diols were obtained with up to 99% ee from the corresponding diketones via the asymmetric reduction using 2.5 molar amounts of diphenylsilane.
- Kuwano, Ryoichi,Sawamura, Masaya,Shirai, Junya,Takahashi, Masatoshi,Ito, Yoshihiko
-
p. 485 - 496
(2007/10/03)
-
- Treatment of diseases mediated by the nitric oxide/cGMP/protein kinase G pathway
-
Disclosed are methods and compositions for stimulating cellular nitric oxide (NO) synthesis, cyclic guanosine monophosphate levels (cGMP), and protein kinase G (PKG) activity for purposes of treating diseases mediated by deficiencies in the NO/cGMP/PKG signal transduction pathway, by administration of various compounds including alcohols, diols and/or triols and their analogues.
- -
-
-
- Tetrahydrofuran antifungals
-
A compound represented by the formula I STR1 wherein X is independently both F or both Cl or one X is independently F and the other is independently Cl; R1 is a straight or branched chain (C3 to C8) alkyl group substituted by one or two groups convertible in vivo into hydroxy moieties, (e.g., a polyether ester, amino acid ester or phosphate ester) thereof or a pharmaceutically acceptable salt thereof and pharmaceutical compositions thereof useful for treating and/or preventing fungal infections are disclosed.
- -
-
-
- Tetrahydrofuran antifungals
-
A compound represented by the formula I STR1 wherein X is independently both F or both Cl or one X is independently F and the other is independently Cl; R1 is a straight or branched chain (C3 to C8) alkyl group substituted by one or two amino acid ester groups (e.g., an amino acid ester group convertible in vivo into a hydroxy group) thereof or a pharmaceutically acceptable salt thereof and pharmaceutical compositions thereof useful for treating and/or preventing fungal infections are disclosed.
- -
-
-
- Hydrogenation of butane-2,3-dione with heterogeneous cinchona modified platinum catalysts: A combination of an enantioselective reaction and kinetic resolution
-
(R)-3-Hydroxybutan-2-one was obtained with 85-90% ee albeit in low yield by the Pt/Al2O3 cinchona catalyzed hydrogenation of butane-2,3-dione by a combination of enantioselective hydrogenation and kinetic resolution.
- Studer, Martin,Okafor, Victor,Blaser, Hans-Ulrich
-
p. 1053 - 1054
(2007/10/03)
-
- Enantioselective Hydrogenation: V. Hydrogenation of Butane-2,3-dione and of 3-Hydroxybutan-2-one Catalysed by Cinchona-Modified Platinum
-
Pt/silica modified by cinchonidine and cinchonine is active for the enantioselective hydrogenation of butane-2,3-dione to butane-2,3-diol in dichloromethane at 268-298 K and 10 bar pressure. Reaction proceeds in three stages. In the first, about 85% of the butane-2,3-dione is converted to 3-hydroxybutan-2-one and 15% to three higher molecular weight products by hydrodimerisation. The initial enantiomeric excess in the hydroxybutanone is modest (20 to 40%(R) with cinchonidine as modifier, 10%(S) with cinchonine as modifier) and dependent on the amount of alkaloid used in catalyst preparation. In the second stage, 3-hydroxybutan-2-one is converted to butane-2,3-diol; a marked kinetic effect is observed whereby the minority enantiomer is converted preferentially to butanediol and the enantiomeric excess in the remaining hydroxybutanone increases dramatically to values in the range 62 to 89%(R) and to 30%(S). Under all conditions, the most abundant stereochemical form of the final product is meso-butane-2,3-dione. In the third stage the three dimers are slowly converted by hydrogenation, dissociation, and further hydrogenation to butane-2,3-diol. In the absence of alkaloid, butane-2,3-dione hydrogenation to racemic products in dichloromethane solution proceeds in two distinct stages with no dimer formation. Butane-2,3-dione hydrogenation has also been studied over Pt/silica modified anaerobically by exposure to cinchonidine in ethanol under propyne at 2 bar. This catalyst is remarkably active for the conversion of diketone to diol in ethanol at 293 K and 10 bar and kinetic selection in the second stage of reaction is again observed. The hydrogenation of racemic 3-hydroxybutan-2-one in dichloromethane over cinchonine-modified Pt/silica at 273 K and 10 to 40 bar pressure also showed kinetic selection, an enantiomeric excess of up to 70%(S) appearing in the reactant as it was consumed. Mechanisms which account for these hydrogenations and dimerisations and for the enantioselectivities observed and their variation are presented. This diketone hydrogenation provides an example of consecutive thermodynamic and kinetic control of enantioselectivity in a multistage catalytic reaction.
- Slipszenko,Griffiths,Johnston,Simons,Vermeer,Wells
-
p. 267 - 276
(2007/10/03)
-
- Tetrahydrofuran antifungals
-
A compound represented by the formula I STR1 wherein X is independently both F or both Cl or one X is independently F and the other is independently Cl; R1 is a straight or branched chain (C3 to C8) alkyl group substituted by one or two phosphate ester groups (e.g., a phosphate ester convertible in vivo into a hydroxy group) thereof or a pharmaceutically acceptable salt thereof and pharmaceutical compositions thereof useful for treating and/or preventing fungal infections are disclosed.
- -
-
-
- Tetrahydrofuran antifungals
-
A compound represented by the formula I STR1 wherein X is independently both F or both Cl or one X is independently F and the other is independently Cl; R1 is a straight or branched chain (C3 to C8) alkyl group substituted by one or two hydroxy moieties, an ether or ester thereof (e.g., a polyether ester amino acid ester or phosphate ester) thereof or a pharmaceutically acceptable salt thereof and pharmaceutical compositions thereof useful for treating and/or preventing fungal infections are disclosed.
- -
-
-
- Hydroxy-substituted antifungals
-
A compound represented by the formula I STR1 wherein X is independently both F or both Cl or one X is independently F and the other is independently Cl; R1 is a straight or branched chain (C3 to C8) alkyl group substituted by one or two hydroxy moieties, an ether or ester thereof (e.g., a polyether ester, heterocyclic ester amino acid ester or phosphate ester) thereof and the carbon with the asterisk (*) has the R or S absolute configuration or a pharmaceutically acceptable salt thereof and pharmaceutical compositions thereof useful for treating and/or preventing fungal infections are disclosed.
- -
-
-
- Tetrahydrofuran antifungals
-
A compound represented by the formula I STR1 wherein X is independently both F or both Cl or one X is independently F and the other is independently Cl; R1 is a straight or branched chain (C3 to C8) alkyl group substituted by one or two polyetyher ester groups (e.g., a polyether ester convertible in vivo into a hydroxy group) thereof or a pharmaceutically acceptable salt thereof and pharmaceutical compositions thereof useful for treating and/or preventing fungal infections are disclosed.
- -
-
-
- Tetrahydrofuran antifungals
-
A compound represented by the formula I STR1 wherein X is independently both F or both Cl or one X is independently F and the other is independently Cl; R1 is a straight or branched chain (C3 to C8) alkyl group substituted by one or two hydroxy moieties, an ether ester (e.g., a polyetherester or phosphate ester) thereof or a pharmaceutically acceptable salt thereof and pharmaceutical compositions thereof useful for treating and/or preventing fungal infections are disclosed.
- -
-
-
- Conversion of meso-2,3-Butanediol into 2-Butanol by Lactobacilli. Stereochemical and Enzymatic Aspects
-
A number of strains of Lactobacillus spp. from foods were screened for their ability to convert meso-2,3-butanediol into 2-butanol. Only three strains of L. brevis transformed the meso-diol into the secondary alcohol. These strains as well as the others unable to metabolize meso-2,3-butanediol exhibited the capacity to hydrogenate 2-butanone to 2-butanol. In both types of lactobacilli, an inverse relationship was observed between the diol or ketone concentration and the abundance of the R form of 2-butanol. This fact has been interpreted in terms of a co-occurrence of two dehydrogenases, both acting on the ketone with different kinetic parameters and opposite enantioselectivities. These results represent a further support to the assumption that 2-butanol present in distillates originates from the enzymatic activity of lactobacilli growing on mashes and give the most likely explanation of the enantiomeric excess of (R)-2-butanol generally found in distillates.
- Speranza, Giovanna,Corti, Sandra,Fontana, Gabriele,Manitto, Paolo,Galli, Antonietta,Scarpellini, Mauro,Chialva, Franco
-
p. 3476 - 3480
(2007/10/03)
-
- Enantioselective hydrolysis of aryl, alicyclic and aliphatic epoxides by Rhodotorula glutinis
-
Enantioselective epoxide hydrolysis by yeasts has been demonstrated for the hydrolysis of several aryl, alicyclic and aliphatic epoxides by a strain of Rhodotorula glutinis. High enantioselectivity was obtained in the hydrolysis of methyl substituted aryl and aliphatic epoxides whereas selectivity towards terminal epoxides in all cases was lower. Homochiral vicinal diols were formed from several methyl substituted epoxides and also from meso epoxides. Kinetic resolution of trans-1-phenyl-1,2-epoxypropane was studied in more detail.
- Weijers, Carel A. G. M.
-
p. 639 - 647
(2007/10/03)
-
- Optical resolution method
-
The present invention provides three optical resolution methods. The first aspect comprises the steps of adding an optically active bifunctional resolving reagent to a bifunctional compound to form a liquid material, precipitating crystals therefrom, and treating the crystals and the liquid material separately with an acidic material, a basic material, or a basic material and an acidic material, to obtain a pair of enantiomers of an optically active bifunctional compound. The second aspect comprises an optical resolution method by which one necessary enantiomer of a pair of enantiomers in an optically active bifunctional compound is exclusively obtained. The third aspect comprises a method for racemizing one unnecessary enantiomer of a pair of enantiomers in an optically active bifunctional compound which is formed by the optical resolution method of the present invention.
- -
-
-
- Asymmetric Hydrosilylation of Symmetrical Diketones Catalyzed by a Rhodium Complex with Trans-Chelating Chiral Diphosphine EtTRAP
-
Asymmetric hydrosilylation of symmetrical diketones with diphenylsilane in the presence of catalytic amount (/ = 100> of rhodium complex coordinated with trans-chelating chiral phosphine ligand EtTRAP gave corresponding optically active symmetrical diols with high enantiomeric excesses.
- Kuwano, Ryoichi,Sawamura, Masaya,Shirai, Junya,Takahashi, Masatoshi,Ito, Yoshihiko
-
p. 5239 - 5242
(2007/10/02)
-
- Sequential Kinetic Resolution of (+/-)-2,3-Butanediol in Organic Solvent Using Lipase From Pseudomonas cepacia.
-
Lipase from Pseudomonas capacia (PCL, Amano PS) catalyzed the enantioselective diacetylation of (+/-)-2,3-butanediol in vinyl acetate.Both acetylation steps favored the (R)-enantiomer (E1 = 12, E2 = 34), thus the reaction is a sequential kinetic resolution.The enantioselectivities of the two steps reinforced one another because both steps proceeded at comparable rates (S = 3) yielding an overall enantioselectivity of approximately 200.A synthetic-scale resolution starting from 2.7 g of (+/-)-2,3-butanediol yielded the diacetate ester of (R)-(-)-butanediol with 96percent ee (1.6 g, 30percent yield) and (S)-(+)-butanediol with 99percent ee (0.63 g, 23percentyield).This preparation is carried out entirely in organic solvent, thereby avoiding the difficult and low yield extraction of 2,3-butanediol from aqueous solution.
- Caron, Gaetan,Kazlauskas, Romas J.
-
p. 1995 - 2000
(2007/10/02)
-
- Regio-, Diastereo-, and Enantioselective Synthesis of vic-Diols via α-Silyl Ketones According to the SAMP/RAMP Hydrazone Method
-
α-Silylated ketones 5 or 10 of high enantiomeric purity (ee>=90percent) are easily available by silylation or silylation/alkylation of ketones 1 or 6, resp., according to the SAMP/RAMP hydrazone method.Reduction of 5 or 10 with L-selectride, followed by oxidative cleavage of the C-Si bond, leads to vic-diols 11-13 with high diastereoselectivity (de>=90percent) and without racemization.The stereoselectivity of the reduction depends on the structure of the α-silyl ketones 5 or 10, the reducing reagents, and the solvents used.Key Words: Ketones, α-silyl / vic-Diols, diastereo- and enantioselective synthesis / SAMP/RAMP Hydrazones / L-Selectride reductions
- Enders, Dieter,Nakai, Shiro
-
p. 219 - 226
(2007/10/02)
-
- Regio-, Diastereo-, and Enantioselective Synthesis of Vicinal Diols via α-Silyl Ketones
-
A new versatile and efficient regio-, diastereo-, and enantioselective synthesis of vicinal diols s-trans-4, s-trans-5, and s-cis-4 is described.Symmetrical ketones are converted into their SAMP- or RAMP-hydrazones which are then silylated with (isopropyloxy)dimethylsilyl chloride, followed by ozonolysis to afford the α-silyl ketones (R)-2 of high enantiomeric purity (ee 90 > 98percent).On the other hand, methyl ketones, after conversion into the corresponding (-)-(S)-1-amino-2-(methoxymethyl)pyrrolidine (SAMP) hydrazones, are silylated and then alkylated with R1 to afford unsymmetrical α-silyl ketones (S)-3 of high enantiomeric purity (ee 90->98percent).The reduction of the above obtained α-silyl ketones with L-Selectride, followed by oxidative cleavage of the C-Si bond gives rise to s-trans-4, s-trans-5, and s-cis-4 with high diastereoselectivity (de 95->98percent) and without racemization (ee >90->98percent).
- Enders, Dieter,Nakai, Shiro
-
p. 1833 - 1836
(2007/10/02)
-
- Intermediates for preparing optically active carboxylic acids
-
A process is described for preparing optically active alpha-arylalkanoic acids consisting of rearranging an optically active ketal of formula STR1 in which the substituents have the meaning given in the description of the invention.
- -
-
-
- Preparation of Optically Active 1,2-Diols and α-Hydroxy Ketones Using Glycerol Dehydrogenase as Catalyst: Limits to Enzyme-Catalyzed Synthesis due to Noncompetitive and Mixed Inhibition by Product
-
Glycerol dehydrogenase (GDH, EC 1.1.1.6, from Enterobacter aerogenes or Cellulomonas sp.) catalyzes the interconversion of analogues of glycerol and dihydroxyacetone.Its substrate specificity is quite different from than of horse liver alcohol dehydrogenase (HLADH), yeast alcohol dehydrogenase, and other alcohol dehydrogenases used in enzyme-catalyzed organic synthesis and is thus a useful new enzymic catalyst for the synthesis of enantiomerically enriched and isotopically labeled organic molecules.This paper illustrates synthetic applications of GDH as a reduction catalyst by the enantioselective reduction of 1-hydroxy-2-propanone and 1-hydroxy-2-butanone to the corresponding R 1,2-diols (ee = 95-98percent). (R)-1,2-Butanediol-2-d1 was prepared by using formate-d1 as the ultimate reducing agent.Comparison of (R)-1,2-butanediol prepared by reduction of 1-hydroxy-2-butanone enzymatically and with actively fermenting bakers' yeast indicated than yield and enantiomeric purity were similar by the two procedures.Reactions proceeding in the direction of substrate oxidation usually suffer from slow rates and incomplete conversions due to product inhibition.The kinetic consequences of product inhibition (competitive, noncompetitive, and mixed) for practical synthetic applications of GDH, HLADH, and other oxidoreductases are analyzed.In general, product inhibition seems the most serious limitation to the use of these enzymes as oxidation catalysts in organic synthesis.
- Lee, Linda G.,Whitesides, George M.
-
-
- PRACTICAL ASYMMETRIC SYNTHESIS OF AKLAVINONE
-
A practical synthesis of (+)-aklavinone, the aglycone of antitumor antibiotic aclacinomycin A, is achieved by using the asymmetric aldol reaction of 6a to 10a as the key step.
- McNamara, James M.,Kishi, Yoshito
-
p. 4685 - 4692
(2007/10/02)
-
