- Chromium-Catalyzed Production of Diols From Olefins
-
Processes for converting an olefin reactant into a diol compound are disclosed, and these processes include the steps of contacting the olefin reactant and a supported chromium catalyst comprising chromium in a hexavalent oxidation state to reduce at least a portion of the supported chromium catalyst to form a reduced chromium catalyst, and hydrolyzing the reduced chromium catalyst to form a reaction product comprising the diol compound. While being contacted, the olefin reactant and the supported chromium catalyst can be irradiated with a light beam at a wavelength in the UV-visible spectrum. Optionally, these processes can further comprise a step of calcining at least a portion of the reduced chromium catalyst to regenerate the supported chromium catalyst.
- -
-
Paragraph 0111
(2021/03/19)
-
- Mo–Catalyzed One-Pot Synthesis of N-Polyheterocycles from Nitroarenes and Glycols with Recycling of the Waste Reduction Byproduct. Substituent-Tuned Photophysical Properties
-
A catalytic domino reduction–imine formation–intramolecular cyclization–oxidation for the general synthesis of a wide variety of biologically relevant N-polyheterocycles, such as quinoxaline- and quinoline-fused derivatives, and phenanthridines, is reported. A simple, easily available, and environmentally friendly dioxomolybdenum(VI) complex has proven to be a highly efficient and versatile catalyst for transforming a broad range of starting nitroarenes involving several redox processes. Not only is this a sustainable, step-economical as well as air- and moisture-tolerant method, but also it is worth highlighting that the waste byproduct generated in the first step of the sequence is recycled and incorporated in the final target molecule, improving the overall synthetic efficiency. Moreover, selected indoloquinoxalines have been photophysically characterized in cyclohexane and toluene with exceptional fluorescence quantum yields above 0.7 for the alkyl derivatives.
- Hernández-Ruiz, Raquel,Rubio-Presa, Rubén,Suárez-Pantiga, Samuel,Pedrosa, María R.,Fernández-Rodríguez, Manuel A.,Tapia, M. José,Sanz, Roberto
-
supporting information
p. 13613 - 13623
(2021/08/23)
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- Synthesis of α-hydroxy ketones and vicinal (R, R)-diols by Bacillus clausii DSM 8716T butanediol dehydrogenase
-
α-hydroxy ketones (HK) and 1,2-diols are important building blocks for fine chemical synthesis. Here, we describe the R-selective 2,3-butanediol dehydrogenase from B. clausii DSM 8716T (BcBDH) that belongs to the metal-dependent medium chain dehydrogenases/reductases family (MDR) and catalyzes the selective asymmetric reduction of prochiral 1,2-diketones to the corresponding HK and, in some cases, the reduction of the same to the corresponding 1,2-diols. Aliphatic diketones, like 2,3-pentanedione, 2,3-hexanedione, 5-methyl-2,3-hexanedione, 3,4-hexanedione and 2,3-heptanedione are well transformed. In addition, surprisingly alkyl phenyl dicarbonyls, like 2-hydroxy-1-phenylpropan-1-one and phenylglyoxal are accepted, whereas their derivatives with two phenyl groups are not substrates. Supplementation of Mn2+ (1 mM) increases BcBDH's activity in biotransformations. Furthermore, the biocatalytic reduction of 5-methyl-2,3-hexanedione to mainly 5-methyl-3-hydroxy-2-hexanone with only small amounts of 5-methyl-2-hydroxy-3-hexanone within an enzyme membrane reactor is demonstrated.
- Bongaerts, Johannes,Jablonski, Melanie,Kipp, Carina Ronja,Molinnus, Denise,Muschallik, Lukas,Pohl, Martina,Sch?ning, Michael J.,Selmer, Thorsten,Siegert, Petra,Wagner, Torsten
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p. 12206 - 12216
(2020/04/20)
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- Method for synthesizing o-glycol compounds by virtue of bifunctional characteristic catalyst
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The invention belongs to the technical field of organic chemical synthesis and particularly relates to a method for synthesizing o-glycol compounds by virtue of a bifunctional characteristic catalyst.The o-glycol compounds are prepared from olefin and an oxidizing agent through reaction under the effect of the bifunctional characteristic catalyst, wherein the bifunctional characteristic catalystcontains the following components in percentage by mass: 25%-75% of a titanium silicalite molecular sieve, 20%-70% of nano-silicon dioxide and 5%-10% of heteropolyacid. The method provided by the invention has the beneficial effects that a process for synthesizing o-glycol by virtue of a traditional two-step method is simplified; the catalyst can still remain good catalytic performance under a long-period operation condition in the method, the raw material conversion rate is high, and the yields of the o-glycol compounds are high; and the olefin raw material conversion rate is 80.2%-94.6%, andthe selectivity of o-glycol generated through reaction is 85.7%-96.3%.
- -
-
Paragraph 0034-0035; 0036-0037; 0039-0045
(2018/04/26)
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- Method for synthesizing vicinal diol compound by virtue of one-step process
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The invention belongs to the technical field of organic chemical synthesis, and in particular relates to a method for synthesizing a vicinal diol compound by virtue of a one-step process. The vicinaldiol compound is obtained by carrying out reaction on olefin and an oxidizing agent in presence of a bifunctional catalyst, wherein the bifunctional catalyst comprises 25-75% of titanium silicalite molecular sieves, 20-70% of nano alumina and 3-8% of boric oxide in percentage by mass with the titanium silicalite molecular sieves, nano alumina and boric oxide as the benchmarks. The method for synthesizing the vicinal diol compound has the advantages that the traditional two-step vicinal diol synthesis technology is simplified; in the synthetic method, a catalyst still maintains good catalytic performance under long-period operation condition, raw material conversion rate is high, and yield of the vicinal diol compound is high; and olefin raw material conversion rate is 80.2-94.6%, and vicinal diol reaction generation selectivity is 85.7-96.3%.
- -
-
Paragraph 0032-0041
(2018/04/26)
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- Structural Study of Bromide-Bridged Pd Chain Complex with Weak CH···O Hydrogen Bonds
-
A novel Br-bridged Pd chain complex, [Pd(hxn)2Br](TsO)2 (2) (TsO– = p-toluenesulfonate), was synthesized from a new in-plane ligand (3S,4S)-3,4-diaminohexane (hxn). 2 forms PdII/PdIV mixed-valence state, as confirmed by single-crystal X-ray structure analysis and polarized Raman spectra. The hxn ligand provides the additional hydrogen bonds (CH···O) between the methyl group of the ligands and the O atoms of TsO– anions, which are weaker than those observed in the chain complex with hydroxy group, [Pd(dabdOH)2Br]Br2 (1).
- Rasel Mian, Mohammad,Iguchi, Hiroaki,Miyata, Momoka,Takaishi, Shinya,Yamakawa, Hiromichi,Terashige, Tsubasa,Miyamoto, Tatsuya,Okamoto, Hiroshi,Yamashita, Masahiro
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p. 646 - 651
(2018/08/06)
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- Method for synthesizing vicinal diol compound which takes hydrocarbon epoxide as raw material
-
The present invention discloses a method for preparing a vicinal diol compound which takes a hydrocarbon epoxide as a raw material. The method takes the hydrocarbon epoxide as the raw material and takes an anion exchange resin as a catalyst. The vicinal diol compound is prepared by using a fixed bed continuous hydrolysis reaction technology. The anion exchange resin is a halogen-substituted macroporous polystyrene-divinyl benzene quaternary ammonium salt type anion exchange resin. The synthesis method is simple, the catalyst can be used many times, the raw material conversion rate is high, and the yield of the vicinal diol compound is high.
- -
-
Paragraph 0027-0028; 0032; 0037
(2017/08/03)
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- Method for synthesizing ortho-diol compound by using macroporous anion exchange resin as catalyst
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The invention discloses a method for synthesizing an ortho-diol compound by using macroporous anion exchange resin as a catalyst. According to the method, hydrocarbon epoxide is used as a raw material, the anion exchange resin is used as the catalyst, and a fixed bed continuous hydrolysis reaction technology is adopted for preparing the ortho-diol compound; the anion exchange resin is halogen ortho-substituted macroporous polystyrene-divinyl benzene quaternary phosphonium salt type anion exchange resin. The synthesis method is simple, the catalyst can be used repeatedly, the conversion rate of the raw material is high, and the yield of the ortho-diol compound is high.
- -
-
Paragraph 0024; 0025; 0026; 0028; 0029; 0030-0035
(2017/05/27)
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- Synthetic method for o-glycol compounds
-
The invention discloses a synthetic method for o-glycol compounds. The method prepares the o-glycol compounds by using a fixed-bed continuous hydrolysis reaction process with hydrocarbon epoxides as raw materials and anion exchange resin as a catalyst, wherein the anion exchange resin is halogen-p-substituted macroporous polystyrene-divinyl benzene quaternary phosphonium salt anion exchange resin. The synthetic method is simple; the catalyst can be repeatedly used a plurality of times; the conversion rate of the raw materials is high; and the yield of the o-glycol compounds is high.
- -
-
Paragraph 0026-0027; 0029-0036
(2017/08/28)
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- Method for preparing vicinal diol compound through ring-opening reaction
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The present invention discloses a method for preparing a vicinal diol compound through a ring-opening reaction. The method takes a hydrocarbons epoxide as a raw material and takes an anion exchange resin as a catalyst. The vicinal diol compound is prepared by using a fixed bed continuous hydrolysis reaction technology. The anion exchange resin is a halogen-substituted macroporous polystyrene-divinyl benzene quaternary ammonium salt type anion exchange resin. The synthesis method is simple, the catalyst can be used many times, the raw material conversion rate is high, and the yield of the vicinal diol compound is high.
- -
-
Paragraph 0015; 0031; 0033; 0036
(2017/03/28)
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- Method of using anion exchange resin as catalyst to synthesize vicinal diol compound
-
The invention discloses a method of using anion exchange resin as a catalyst to synthesize a vicinal diol compound. The method includes: using hydrocarbon epoxide as a raw material and the anion exchange resin as the catalyst; adopting a fixed bed continuous hydrolysis reaction process to obtain the vicinal diol compound, wherein the anion exchange resin is halogen substituted macroporous polystyrene-divinyl benzene quaternary ammonium salt type anion exchange resin. The method is simple, the catalyst can be utilized repeatedly, the raw material is high in conversion rate, and the vicinal diol compound is high in yield.
- -
-
Paragraph 0027; 0029; 0030; 0036
(2017/07/06)
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- Assessing the stereoselectivity of: Serratia marcescens CECT 977 2,3-butanediol dehydrogenase
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α-Hydroxy ketones and vicinal diols constitute well-known building blocks in organic synthesis. Here we describe one enzyme that enables the enantioselective synthesis of both building blocks starting from diketones. The enzyme 2,3-butanediol dehydrogenase (BudC) from S. marcescens CECT 977 belongs to the NADH-dependent metal-independent short-chain dehydrogenases/reductases family (SDR) and catalyses the selective asymmetric reductions of prochiral α-diketones to the corresponding α-hydroxy ketones and diols. BudC is highly active towards structurally diverse diketones in combination with nicotinamide cofactor regeneration systems. Aliphatic diketones, cyclic diketones and alkyl phenyl diketones are well accepted, whereas their derivatives possessing two bulky groups are not converted. In the reverse reaction vicinal diols are preferred over other substrates with hydroxy/keto groups in non-vicinal positions.
- Médici, Rosario,Stammes, Hanna,Kwakernaak, Stender,Otten, Linda G.,Hanefeld, Ulf
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p. 1831 - 1837
(2017/07/15)
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- Hydrogen Bonding-Assisted Enhancement of the Reaction Rate and Selectivity in the Kinetic Resolution of d,l-1,2-Diols with Chiral Nucleophilic Catalysts
-
An extremely efficient acylative kinetic resolution of d,l-1,2-diols in the presence of only 0.5 mol% of binaphthyl-based chiral N,N-4-dimethylaminopyridine was developed (selectivity factor of up to 180). Several key experiments revealed that hydrogen bonding between the tert-alcohol unit(s) of the catalyst and the 1,2-diol unit of the substrate is critical for accelerating the rate of monoacylation and achieving high enantioselectivity. This catalytic system can be applied to a wide range of substrates involving racemic acyclic and cyclic 1,2-diols with high selectivity factors. The kinetic resolution of d,l-hydrobenzoin and trans-1,2-cyclohexanediol on a multigram scale (10 g) also proceeded with high selectivity and under moderate reaction conditions: (i) very low catalyst loading (0.1 mol%); (ii) an easily achievable low reaction temperature (0 °C); (iii) high substrate concentration (1.0 M); and (iv) short reaction time (30 min). (Figure presented.).
- Fujii, Kazuki,Mitsudo, Koichi,Mandai, Hiroki,Suga, Seiji
-
supporting information
p. 2778 - 2788
(2017/08/23)
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- Amine Catalysis for the Organocatalytic Diboration of Challenging Alkenes
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The generation of in situ sp2–sp3diboron adducts has revolutionised the synthesis of organoboranes. Organocatalytic diboration reactions have represented a milestone in terms of unpredictable reactivity of these adducts. However, current methodologies have limitations in terms of substrate scope, selectivity and functional group tolerance. Here a new methodology based on the use of simple amines as catalyst is reported. This methodology provides a completely selective transformation overcoming current substrate scope and functional/protecting group limitations. Mechanistic studies have been included in this report.
- Farre, Albert,Soares, Kaline,Briggs, Rachel A.,Balanta, Angelica,Benoit, David M.,Bonet, Amadeu
-
supporting information
p. 17552 - 17556
(2016/11/28)
-
- Hydrodeoxygenation of vicinal OH groups over heterogeneous rhenium catalyst promoted by palladium and ceria support
-
Heterogeneous ReOx-Pd/CeO2 catalyst showed excellent performance for simultaneous hydrodeoxygenation of vicinal OH groups. High yield (> 99%), turnover frequency (300 h-1), and turnover number (10 000) are achieved in the reaction of 1,4-anhydroerythritol to tetrahydrofuran. This catalyst can be applied to sugar alcohols, and mono-alcohols and diols are obtained in high yields (≥ 85%) from substrates with even and odd numbers of OH groups, respectively. The high catalytic performance of ReOx-Pd/CeO2 can be assigned to rhenium species with + 4 or + 5 valence state, and the formation of this species is promoted by H2/Pd and the ceria support.
- Ota, Nobuhiko,Tamura, Masazumi,Nakagawa, Yoshinao,Okumura, Kazu,Tomishige, Keiichi
-
supporting information
p. 1897 - 1900
(2015/02/19)
-
- Alcohol cross-coupling for the kinetic resolution of diols via oxidative esterification
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We present an organocatalytic C-O-bond cross-coupling strategy to kinetically resolve racemic diols with aromatic and aliphatic alcohols, yielding enantioenriched esters. This one-pot protocol utilizes an oligopeptide multicatalyst, m-CPBA as the oxidant, and N,N-diisopropylcarbodiimide as the activating agent. Racemic acyclic diols as well as trans-cycloalkane-1,2-diols were kinetically resolved, achieving high selectivities and good yields for the products and recovered diols.
- Hofmann, Christine,Schümann, Jan M.,Schreiner, Peter R.
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p. 1972 - 1978
(2015/02/19)
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- Synthesis of ferrocene derivatives with planar chirality via palladium-catalyzed enantioselective C-H bond activation
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The first catalytic and enantioselective C-H direct acylation of ferrocene derivatives has been developed. A series of 2-acyl-1-dimethylaminomethylferrocenes with planar chirality were provided under highly efficient and concise one-pot conditions with up to 85% yield and 98% ee. The products obtained could be easily converted to various chiral ligands via diverse transformations.
- Pi, Chao,Cui, Xiuling,Liu, Xiuyan,Guo, Mengxing,Zhang, Hanyu,Wu, Yangjie
-
supporting information
p. 5164 - 5167
(2014/12/11)
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- Rabbit 3-hydroxyhexobarbital dehydrogenase is a NADPH-preferring reductase with broad substrate specificity for ketosteroids, prostaglandin D2, and other endogenous and xenobiotic carbonyl compounds
-
3-Hydroxyhexobarbital dehydrogenase (3HBD) catalyzes NAD(P) +-linked oxidation of 3-hydroxyhexobarbital into 3-oxohexobarbital. The enzyme has been thought to act as a dehydrogenase for xenobiotic alcohols and some hydroxysteroids, but its physiological function remains unknown. We have purified rabbit 3HBD, isolated its cDNA, and examined its specificity for coenzymes and substrates, reaction directionality and tissue distribution. 3HBD is a member (AKR1C29) of the aldo-keto reductase (AKR) superfamily, and exhibited high preference for NADP(H) over NAD(H) at a physiological pH of 7.4. In the NADPH-linked reduction, 3HBD showed broad substrate specificity for a variety of quinones, ketones and aldehydes, including 3-, 17- and 20-ketosteroids and prostaglandin D2, which were converted to 3α-, 17β- and 20α-hydroxysteroids and 9α,11β- prostaglandin F2, respectively. Especially, α-diketones (such as isatin and diacetyl) and lipid peroxidation-derived aldehydes (such as 4-oxo- and 4-hydroxy-2-nonenals) were excellent substrates showing low Km values (0.1-5.9 μM). In 3HBD-overexpressed cells, 3-oxohexobarbital and 5β-androstan-3α-ol-17-one were metabolized into 3-hydroxyhexobarbital and 5β-androstane-3α,17β-diol, respectively, but the reverse reactions did not proceed. The overexpression of the enzyme in the cells decreased the cytotoxicity of 4-oxo-2-nonenal. The mRNA for 3HBD was ubiquitously expressed in rabbit tissues. The results suggest that 3HBD is an NADPH-preferring reductase, and plays roles in the metabolisms of steroids, prostaglandin D2, carbohydrates and xenobiotics, as well as a defense system, protecting against reactive carbonyl compounds.
- Endo, Satoshi,Matsunaga, Toshiyuki,Matsumoto, Atsuko,Arai, Yuki,Ohno, Satoshi,El-Kabbani, Ossama,Tajima, Kazuo,Bunai, Yasuo,Yamano, Shigeru,Hara, Akira,Kitade, Yukio
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p. 1366 - 1375
(2013/11/19)
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- Biocatalytic production of alpha-hydroxy ketones and vicinal diols by yeast and human aldo-keto reductases
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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.
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p. 195 - 203
(2013/05/08)
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- Enantiomerically enriched trans-diols from alkenes in one pot: A multicatalyst approach
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Multicatalysts consisting of non-natural oligopeptides with distinctly different catalytic moieties create molecular complexity in a multistep one-pot sequence starting from simple alkenes yielding highly enantiomerically enriched trans-diols. The Royal Society of Chemistry 2012.
- Hrdina, Radim,Mueller, Christian E.,Wende, Raffael C.,Wanka, Lukas,Schreiner, Peter R.
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supporting information; experimental part
p. 2498 - 2500
(2012/04/10)
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- Pt-based chiral organotin modified heterogeneous catalysts for the enantioselective hydrogenation of 3,4-hexanedione
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In this paper we have studied the liquid-phase enantioselective hydrogenation of 3,4-hexanedione using Pt-based catalysts, modified with chiral organotin compounds derived from the (-)-menthyl group: (-)-Pt-MenSnBu 3 and (-)-Men3Sn-Sn-(-)-Men3. The organotin chiral modifiers were carefully synthesized and characterized in order to obtain optically pure compounds. The catalysts were prepared through a controlled surface reaction between the supported transition metal and the organometallic compound, using techniques derived from Surface Organometallic Chemistry on Metals (SOMC/M). The organobimetallic catalytic systems were found to be active and enantioselective in the hydrogenation of 3,4-hexanedione, yielding an enantiomeric excess of 25-27% for 4-hydroxy-3-hexanone.
- Vetere, Virginia,Faraoni, María B.,Podestá, Julio C.,Casella, Mónica L.
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p. 209 - 214
(2013/02/23)
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- Highly efficient and stereoselective biosynthesis of (2S,5S)-hexanediol with a dehydrogenase from Saccharomyces cerevisiae
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The enantiopure (2S,5S)-hexanediol serves as a versatile building block for the production of various fine chemicals and pharmaceuticals. For industrial and commercial scale, the diol is currently obtained through bakers' yeast-mediated reduction of 2,5-hexanedione. However, this process suffers from its insufficient space-time yield of about 4 g L-1 d-1 (2S,5S)-hexanediol. Thus, a new synthesis route is required that allows for higher volumetric productivity. For this reason, the enzyme which is responsible for 2,5-hexanedione reduction in bakers' yeast was identified after purification to homogeneity and subsequent MALDI-TOF mass spectroscopy analysis. As a result, the dehydrogenase Gre2p was shown to be responsible for the majority of the diketone reduction, by comparison to a Gre2p deletion strain lacking activity towards 2,5-hexanedione. Bioreduction using the recombinant enzyme afforded the (2S,5S)-hexanediol with >99% conversion yield and in >99.9% de and ee. Moreover, the diol was obtained with an unsurpassed high volumetric productivity of 70 g L-1 d-1 (2S,5S)-hexanediol. Michaelis-Menten kinetic studies have shown that Gre2p is capable of catalysing both the reduction of 2,5-hexanedione as well as the oxidation of (2S,5S)-hexanediol, but the catalytic efficiency of the reduction is three times higher. Furthermore, the enzyme's ability to reduce other keto-compounds, including further diketones, was studied, revealing that the application can be extended to α-diketones and aldehydes.
- Mueller, Marion,Katzberg, Michael,Bertau, Martin,Hummel, Werner
-
experimental part
p. 1540 - 1550
(2010/07/04)
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- Asymmetric hydrogenation of 3,4-hexanedione over PtSn catalysts
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In this work, some results of the liquid-phase racemic and enantioselective hydrogenation of 3,4-hexanedione are presented. The catalysts employed were platinum-based, supported on SiO2. Monometallic catalysts were modified with organotin precu
- Vetere, Virginia,Faraoni, Maria B.,Podesta, Julio C.,Casella, Monica L.
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experimental part
p. 34 - 39
(2010/11/03)
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- Regio- and stereoselective reduction of diketones and oxidation of diols by biocatalytic hydrogen transfer
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The asymmetric reduction of symmetrical and nonsymmetrical diketones as well as the stereoselective oxidation of various diols by biocatalytic hydrogen transfer was investigated by employing lyophilized cells of Rhodococcus ruber DSM 44541 containing alcohol dehydrogense ADH-'A'. Symmetrical and nonsymmetrical diketones at the (ω-1)- and (ω-2)-positions are reduced to the Prelog product with high stereopreference, while sterically more demanding ketone moieties, for example those at the (ω-3)-position, remain unchanged. For the oxidation mode, differentiation between primary and secondary alcohols is achieved, and the (S)-configured secondary alcohols at the (ω-1)- and (ω-2)-positions are oxidized preferentially. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Edegger, Klaus,Stampfer, Wolfgang,Seisser, Birgit,Faber, Kurt,Mayer, Sandra F.,Oehrlein, Reinhold,Hafner, Andreas,Kroutil, Wolfgang
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p. 1904 - 1909
(2007/10/03)
-
- Copper ion-induced activation and asymmetric benzoylation of 1,2-diols: Kinetic chiral molecular recognition
-
New catalytic ability of copper(II) ion has been exploited for monobenzoylation of 1,2-diols. The catalyst can be readily modified by ligation to acquire higher stereoselectivity. Highly effective kinetic resolution of dl-1,2-diols was achieved. The enant
- Matsumura, Yoshihiro,Maki, Toshihide,Murakami, Sachie,Onomura, Osamu
-
p. 2052 - 2053
(2007/10/03)
-
- A mechanistically designed cinchona alkaloid ligand in the osmium catalyzed asymmetric dihydroxylation of alkenes
-
A new ligand has been designed using dihydroquinine as the chiral controller for asymmetric dihydroxylation of alkenes. The purpose of this design of the ligand is to find out the transition state involved in the mechanism of asymmetric dihydroxylation, which may shed some light to differentiate between the hypothesis put forward by Sharpless' and Corey's groups. The present study supports the hypothesis proposed by Sharpless et al. and it appears that the L shaped cleft may be involved in governing the high selectivity of asymmetric dihydroxylation of alkenes.
- Lohray,Singh,Bhushan
-
p. 1226 - 1233
(2007/10/03)
-
- 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)
-
- Synthesis of (3R,4R)-Hexane-3,4-diol from D-Mannitol
-
(3R,4R)-Hexane-3,4-diol was synthesized from D-mannitol by using a strategy of protection and deprotection of hydroxyl groups.
- Saravanan,Singh, Vinod K.
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p. 497 - 497
(2007/10/03)
-
- Kinetic resolution of vic-diols by Bacillus stearothermophilus diacetyl reductase
-
The kinetic resolution of several racemic syn- and anti-1,2-diols by enzymatic oxidation with Bacillus stearothermophilus diacetyl reductase is described. The enantiomerically pure (R,R)- and (R,S)-diols are recovered in almost quantitative yield.
- Bortolini, Olga,Casanova, Elena,Fantin, Giancarlo,Medici, Alessandro,Poli, Silvia,Hanau, Stefania
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p. 647 - 651
(2007/10/03)
-
- -
-
The microbioloaical reduction of 3.A-diketones has been studied and some optically pure 3-hydroxy-4-ketones and 3,4-diols have been isolated with good yields. The chiral products of the reduction, which could not be obtained by direct action of microorganisms, were prepared by chemoenzymatic synthesis based on the microbiological reduction of a-ketothioacetals. The stereomers of non-8-ene-3,4-dials obtained by these methods were used for synthesizing the enantiomers of two pheromones: exo-fcreuzcomm and cndo-brevicomin. Eisevier,.
- Bel-Rhlid, Rachid,Renard, Michel F.,Veschambre, Henri
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p. 1011 - 1021
(2007/10/03)
-
- Origin of α-Hydroxy Ketones in the Osmium Tetroxide-Catalyzed Asymmetric Dihydroxylation of Alkenes
-
The origin and the mechanism of formation of α-hydroxy ketones in the osmium tetroxide-catalyzed asymmetric cis-dihydroxylation (ADH) of alkenes in the presence of tert-butyl hydroperoxide is described.The formation of α-hydroxy ketones has been established to proceed through either the hydration of monooxobisglycolate ester 2 followed by oxidation with tert-butyl hydroperoxide (TBHP) or by acid-catalyzed addition of TBHP on the intermediate bisglycolate ester 2.On the basis of the mechanistic insight, it has been possible to shut down the formation of α-hydroxy ketones and other side products in the ADH reaction, even when TBHP is used as an oxygen source.It is possible to prepare α-hydroxy ketones in good yields but the optical purity of ketols has been found to be very low, which not only shed significant light on the mechanism of their formation, but also delineated the improbability of syntesizing them in optically active forms by ADH reaction of alkenes.
- Lohray, Braj B.,Bhushan, Vidya,Kumar, R. Krishna
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p. 1375 - 1380
(2007/10/02)
-
- A Mechanistically Designed Mono-cinchona Alkaloid Is An Excellent Catalyst for the Enantioselective Dihydroxylation of Olefins
-
On the basis of ideas recently advanced regarding the origin of enantioselectivity in the OsO4 promoted dihydroxylation of olefins catalyzed by bis-cinchona alkaloid derivatives such as 1, specifically strong evidence for reaction via transition state assembly 2, the mono-quinidine derivative 3 was selected as a promising catalytic ligand.The experimental observation of high enantioselectivity promoted by 3 provides additional evidence in favor of transition-state 2.
- Corey, E. J.,Noe, Mark C.,Grogan, Michael J.
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p. 6427 - 6430
(2007/10/02)
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- The Synthesis of Glycols by Mercury-Photosensitized Alcohol Dehydrodimerization
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A variety of alcohols can be dehydrodimerized to give 1,2-diols on a multigram scale at 1 atm pressure and reflux temperature on photolysis (254 nm) in the presence of a trace of Hg vapor.Initial C-H bond breaking is followed by recombination of the resulting α-centered radicals, which normally leads to C-C bond formation α to oxygen.The reaction rate and selectivity can be increased by operating at lower temperatures under H2, in which case H atoms replace Hg* as the principal abstracting reagent and H atom abstraction from the α-CH bond leads directly to the α-C-centered radical.Under H atom conditions, unsaturated alcohols also react, in which case diols other than the 1,2-isomer can be formed selectively.The product can be rationalized on the basis of H atom addition to the C=C double bond to give the most stable radical which then dimerizes.For the special case of t-BuOH, H atom abstraction from the t-BuOH β-CH group under H atom conditions leads to the β-centered radical, which dimerizes to the 1,4-diol.Radical disproportionation accounts for some of the byproducts observed.The following previously unknown C-H bond strengths (kcal/mol) were determined from the results, assuming the literature BDE for the α-C-H of 2-propanol (91.0 +/-1.0); n-butanol, 92.8 +/- 1.0( α), 95.2 +/- 1.0 (β), and 94.3 +/- 1.0 (γ); n-propanol, 93.1 +/- 1.0 (α), and 95.0 +/- 1.0 (β), respectively.
- Lee, Jesse C.,Boojamra, Constantine G.,Crabtree, Robert H.
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p. 3895 - 3900
(2007/10/02)
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- Highly enantioselective dihydroxylation of olefins by osmium tetroxide with chiral diamines
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Enantioselective dihydroxylation of olefins by osmium tetroxide with chiral diamines was examined. The hydroxylation employing 1 gave exceptionally high optical yields in the production of diols from mono-, trans-di-, and trisubstituted olefins. Virtually complete asymmetric induction was observed in the reaction of trans-β-methylstyrene. The stereochemical outcome of the asymmetric reaction strongly suggested that the oxidation proceeded via organometallacycle 14.
- Nakajima,Tomioka,Iitaka,Koga
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p. 10793 - 10806
(2007/10/02)
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- Asymmetric Dihydroxylation of Olefins with a Simple Chiral Ligand
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A C2 symmetrical chiral ligand derived from (R,R)-trans-1,2-diaminocyclohexane is highly effective in the asymmetric cis-dihydroxylation of aromatic and aliphatic di- and trisubstituted olefins under stoichiometric conditions.
- Hanessian, Stephen,Meffre, Patrick,Girard, Mario,Beaudoin, Serge,Sanceau, Jean-Yves,Bennani, Youssef
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p. 1991 - 1993
(2007/10/02)
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- On the Mechanism of Osmium Catalyzed Asymmetric Dihydroxylation (ADH) of Alkenes
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Dihydroquinidine and dihydroquinine bisesters of malonic acid, adipic acid and terephthalic acid are used as chiral auxiliaries for osmium tetroxide catalyzed asymmetric dihydroxylation of alkenes.Highly stereoselective osmylation of alkenes has been rationalized on the basis of ?-? interaction of the alkenes with the ligand.
- Lohray, Braj. B.,Bhushan, Vidya
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p. 5113 - 5116
(2007/10/02)
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- Synthesis of chiral nonracemic diols via nucleophilic opening of (S,S)-1,2,3,4-diepoxybutane
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(S,S)-1,2,3,4-diepoxybutane was synthesized from (R,R)-dimethyl tartrate. Nucleophilic opening of this diepoxybutane gave a convenient method for generating a variety of chiral nonracemic diols.
- Devine, Paul N.,Oh, Taeboem
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p. 883 - 886
(2007/10/02)
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- Ligand-based improvement of enantioselectivity in the catalytic asymmetric dihydroxylation of dialkyl substituted olefins
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A high level of asymmetric induction was achieved in the asymmetric dihydroxylation of dialkyl substituted olefins using 9-O-aryldihydroquinidines as ligands.
- Shibata, Tomoyuki,Gilheany, Declan G.,Blackburn, Brent K.,Barry Sharpless
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p. 3817 - 3820
(2007/10/02)
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- Alkane Functionalization on a Preparative Scale by Mercury-Photosensitized Cross-Dehydrodimerization
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Alkanes can be functionalized with high conversions and in high chemical and quantum yields on a multigram scale by mercury-photosensitized reaction between an alkane and alcohols, ethers, or silanes to give homodimers and cross-dehydrodimers.The separation of the product mixtures is often particulary easy because of a great difference in polarity of the homodimers and cross-dimers.It is also possible to bias the product composition when the ratio of the components in the vapor phase is adjusted by altering the liquid composition.This is useful either to maximize chemical yield or to ease separation by favoring the formation of the most easily separated pair of compounds.The mechanistic basis of the reaction is discussed and a number of specific types of syntheses, for example of 2,2-disubstituted carbinols, are described in detail.The selectivity of cross-dimerization is shown to exceed that for homodimerization and reasons are discussed.Relative reactivities of different compounds and classes of compound are MeOHp-dioxanecyclohexane1,3,5-trioxacyclohexaneethanolisobutaneTHFEt3SiH.The observed selectivities generally parallel those for homodimerization, reported in the preceding paper, but certain differences are noted, and reasons for the differences are proposed.The bond-dissociation energy of Et3SiH is estimated from the reactivity data to be 90 kcal/mol.Eleven new carbinols are synthesized.
- Brown, Stephen H.,Crabtree, Robert H.
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p. 2946 - 2953
(2007/10/02)
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- A Convenient Catalytic Method for the Dihydroxylation of Alkenes by Hydrogen Peroxide
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A simple method for preparing water-soluble vicinal diols from the corresponding water-insoluble alkenes is reported.It is based on the use of tungsten peroxo complexes as catalysts and hydrogen peroxide as the oxidizing agent in a two-phase system.
- Venturello, Carlo,Gambaro, Mario
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p. 295 - 297
(2007/10/02)
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- Making Mercury-Ptotosensitized Dehydrodimerization into an Organic Synthetic Method: Vapor Pressure Selectivity and the Behavior of Functionalized Substrates
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Mercury-photosensitized dehydrodimerization in the vapor phase can be made synthetically useful by taking advantage of a simple reflux apparatus (Figure 1), in which the products promptly condense and are protected from further conversion.This vapor pressure selectivity gives high chemical selectivity even at high conversion and on a multigram scale.Mercury absorbs 254-nm light to give the 3P1 excited state (Hg*), which homolyses a C-H bond of the substrate with a 3o>2o>1o selectivity.Quantitative prediction of product mixtures in alkane dimerization and in alkane-alkane cross-dimerizations is discussed.Radical disproportionation gives alkene, but this intermediate is recycled back into the radical pool via H atom attack, which is beneficial both for yield and selectivity.The method is very efficient at constructing C-C bonds between highly substituted carbon atoms, yet the method fails if a dimer has four sets of obligatory 1,3-syn methyl-methyl steric repulsions, as in the unknown 2,3,4,4,5,5,6,7-octamethyloctane.We have extended the range of substrates susceptible to the reaction, for example to higher alcohols, ethers, silanes, partially fluorinated alcohols, and partially fluorinated ethers.We see selectivity for dimers involving C-H bonds α to O or N and for S-H over C-H.An important advantage of our experimental conditions in the case of alcohols is that the aldehyde or ketone disproportionation product (which is not subject to H. attack) is swept out of the system by the stream of H2 also produced, so it does not remain and inhibit the rate and lower the selectivity. kdis/krec is estimated for a number of radicals studied.The very hindered 3o 1,4-dimethylcyclohex-1-yl radical is notable in having a kdis/krec as high as 7.1.
- Brown, Stephen H.,Crabtree, Robert H.
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p. 2935 - 2946
(2007/10/02)
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- Intermediates for preparing optically active carboxylic acids
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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.
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- Highly Enantioselective Dihydroxylation of Trans-Disubstituted and Monosubstituted Olefins
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Extremely high levels of asymmetric induction have been achieved in osmium tetraoxide oxidation of trans-disubstituted and monosubstituted olefins by using chiral N,N'-dineohexyl-2,2'-bipyrrolidine ligand.
- Oishi, Tohru,Hirama, Masahiro
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p. 5834 - 5835
(2007/10/02)
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- Asymmetric Dihyroxylation of Alkenes with Osmium Tetroxide: Chiral N,N'-Dialkyl-2,2'-bipyrrolidine Complex
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Asymmetric osmylation of alkenes by using N,N'-dialkyl-2,2'-bipyrrolidines as the chiral ligands shows a high asymmetric induction and a marked dependence of the enantioselectivity on both the N-alkyl group and the reaction solvent.
- Hirama, Masahiro,Oishi, Tohru,Ito, Sho
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p. 665 - 666
(2007/10/02)
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