- Microwave assisted bi-functional activation of β-bromo-tert-alcohols
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Microwave-assisted dehydration-oxidation of β-bromo-tert-alcohols to afford 2,3-unsaturated ketones in good yield is reported. The reaction of substrates with DMSO in 1:1 ratio (w/v) is promoted by ZnS in a solvent-free condition. A concurrent bi-functional activation of trans-vicinal bromo- and hydroxyl groups with ZnS is elucidated. This is a new observation under microwave and applies to β-bromo-tert-alcohols derived from 1,4-disubstitued-1-cyclohexenes. It is very useful in the synthesis of 2,3-unsaturated ketones derived from monoterpenes which are valuable flavour compounds. [Figure not available: see fulltext.]
- Kannan, Nandini,Rangaswamy, Manjunatha Javagal,Kemapaiah, Bettadaiah Bheemanakere
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- Kinetics of the Aqueous Phase Reactions of Atmospherically Relevant Monoterpene Epoxides
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Laboratory and field measurements have demonstrated that an isoprene-derived epoxide intermediate (IEPOX) is the origin of a wide range of chemical species found in ambient secondary organic aerosol (SOA). In order to explore the potential relevance of a similar mechanism for the formation of monoterpene-derived SOA, nuclear magnetic resonance techniques were used to study kinetics and reaction products of the aqueous-phase reactions of several monoterpene epoxides: β-pinene oxide, limonene oxide, and limonene dioxide. The present results, combined with a previous study of α-pinene oxide, indicate that all of these epoxides will react more quickly than IEPOX with aqueous atmospheric particles, even under low-acidity conditions. As for α-pinene oxide, the observed products can be mainly rationalized with a hydrolysis mechanism, and no long-lived organosulfate or nitrate species nor species that retain the β-pinene bicyclic carbon backbone are observed. As bicyclic ring-retaining organosulfate and nitrate species have been previously observed in monoterpene-derived SOA, it appears that monoterpene-derived epoxides may not be as versatile as IEPOX in producing a range of SOA species, and other mechanisms are needed to rationalize organosulfate and nitrate formation.
- Cortés, DIego A.,Elrod, Matthew J.
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- A 38 kDa allylic alcohol dehydrogenase from the cultured cells of Nicotiana tabacum
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An NADP+-dependent alcohol dehydrogenase (allyl-ADH) was isolated from the cultured cells of Nicotiana tabacum. The allyl-ADH was found to be efficient for the dehydrogenation of secondary allylic alcohols rather than saturated secondary alcohols and it was specific for the S-stereoisomer of the alcohols. The enzyme catalyzed the reversible reaction whereby the carbonyl group of enones is reduced to the corresponding allylic alcohol or vice versa. Two possible primary structures of the allyl-ADH were deduced by the sequence analyses of full-length cDNAs (ally-ADH1 and ally-ADH2), which were cloned by the PCR method. These analyses indicated that the allyl-ADHs are composed of 343 amino acids-having the molecular weights 38 083 and 37 994, respectively, and they showed approximately 70% homology to the NADP+-dependent oxidoreductases belonging to a plant ζ-crystallin family. (C) 2000 Elsevier Science Ltd.
- Hirata, Toshifumi,Tamura, Yoshitaka,Yokobatake, Naoyuki,Shimoda, Kei,Ashida, Yoshiyuki
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- Green production of polymer-supported PdNPs: Application to the environmentally benign catalyzed synthesis of cis-3-hexen-1-ol under flow conditions
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Pd nanoparticles generated on gel type ion-exchange resins under catalytic conditions show high activity, selectivity and durability in partial hydrogenation reactions under mild conditions, thus providing a green, low-cost option for fine-chemicals production. The application to the continuous-flow synthesis of the leaf alcohol fragrance cis-3-hexen-1-ol is demonstrated.
- Moreno-Marrodan, Carmen,Barbaro, Pierluigi,Catalano, Massimo,Taurino, Antonietta
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- Stereoselective reduction of (R)-(-)-carvone with sodium dithionite in the presence of cyclomaltoheptaose (β-cyclodextrin) and its heptakis(2,6-di-O-methyl) derivative
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The authors have studied the competition between l,4 and l,2-reduction of the conjugated enone (r)-(-)-carvone in the presence of cyclomaltoheptaose and its heptakis derivative using sodium dithionite as a reducing agent in aqueous sodium hydrogen carbonate with or without benzene. The spectrum of products namely the ketones and the alcohols expected from the non-selective reduction of an organic compound is shown.
- Fornasier,Marcuzzi,Parmagnani,Tonellato
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- Heteropoly acid catalysis for the isomerization of biomass-derived limonene oxide and kinetic separation of the trans-isomer in green solvents
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Terpenes are an abundant class of natural products, which is important for flavor and fragrance industry. Many acid catalyzed reactions used for upgrading terpenes still involve mineral acids as homogeneous catalysts and/or toxic solvents. Heteropoly acids represent a well-established eco-friendly alternative to conventional acid catalysts. As these reactions are usually performed in the liquid phase, solvents play a critical role for the process sustainability. In the present work, we developed a catalytic route to valuable fragrance ingredients, dihydrocarvone and carvenone, from limonene oxide by its isomerization using silica-supported tungstophosphoric acid as a heterogeneous catalyst and dialkylcarbonates as green solvents. The reaction pathway can be switched between dihydrocarvone and carvenone (obtained in 90% yield each) simply by changing the reaction temperature. In addition, we developed an efficient method for kinetic separation of trans-limonene oxide from commercial cis/trans-limonene oxide mixture and stereoselective synthesis of trans-dihydrocarvone.
- Cotta, Rafaela F.,Martins, Rafael A.,Pereira, Matheus M.,da Silva Rocha, Kelly A.,Kozhevnikova, Elena F.,Kozhevnikov, Ivan V.,Gusevskaya, Elena V.
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- Stereodivergent Synthesis of Carveol and Dihydrocarveol through Ketoreductases/Ene-Reductases Catalyzed Asymmetric Reduction
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Chiral carveol and dihydrocarveol are important additives in the flavor industry and building blocks in the synthesis of natural products. Despite the remarkable progress in asymmetric catalysis, convenient access to all possible stereoisomers of carveol and dihydrocarveol remains a challenge. Here, we present the stereodivergent synthesis of carveol and dihydrocarveol through ketoreductases/ene-reductases catalyzed asymmetric reduction. By directly asymmetric reduction of (R)- and (S)-carvone using ketoreductases, which have Prelog or anti-Prelog stereopreference, all four possible stereoisomers of carveol with medium to high diastereomeric excesses (up to >99 %) were first observed. Then four stereoisomers of dihydrocarvone were prepared through ene-reductases catalyzed diastereoselective synthesis. Asymmetric reduction of obtained dihydrocarvone isomers by ketoreductases further provide access to all eight stereoisomeric dihydrocarveol with up to 95 % de values. In addition, the absolute configurations of dihydrocarveol stereoisomers were determined by using modified Mosher's method.
- Guo, Jiyang,Zhang, Rui,Ouyang, Jingping,Zhang, Feiting,Qin, Fengyu,Liu, Guigao,Zhang, Wenhe,Li, Hengyu,Ji, Xiaohong,Jia, Xian,Qin, Bin,You, Song
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- Selective carvone hydrogenation to dihydrocarvone over titania supported gold catalyst
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Selective hydrogenation of natural carvone to industrially valuable dihydrocarvone was carried out at 100°C under hydrogen pressure over a 1.9wt.% Au/TiO2 catalyst. The gold catalyst has demonstrated high activity as well as stereo- and chemoselectivity in conjugated C=C double bond hydrogenation with predominant formation of trans-dihydrocarvone. The catalytic activity and trans-to cis-isomers ratio were shown to strongly depend on the solvent. In a range of C1 - C3 alcohol solvents both catalytic activity and trans-to cis-dihydrocarvone ratio increased following the order: 2-propanol a nearly complete carvone conversion (90%) after 13h in the case of methanol, with the trans-to cis-dihydrocarvone ratio being about 1.8. Based on the transition state theory a quantitative description of trans-to cis-dihydrocarvone ratio variations in different solvents was made.
- Demidova,Suslov,Simakova,Simakova,Volcho,Salakhutdinov,Murzin
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- Direct conversion of tert-β-bromo alcohols to ketones with zinc sulfide and DMSO
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tert-β-Bromo alcohols, derived from simple monoterpene hydrocarbons, react with zinc sulfide in dimethyl sulfoxide to afford saturated ketones as the major and hydroxy ketones as the minor products. The reaction involves initial nucleophilic attack by DMSO on the carbon attached to the halogen, which is assisted by electrophilic zinc sulfide. Subsequent Kornblum type oxidation yields the α-hydroxy ketone. On the other hand, abstraction of proton β to the hydroxyl group followed by an attack of the neighboring hydroxyl moiety on the sulfur of the dimethylsulfoxonium intermediate and its subsequent collapse yields an enol, which tautomerizes to a saturated ketone. The latter pathway is predominantly followed.
- Bettadaiah,Gurudutt,Srinivas
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- REGIOSPECIFIC RDUCTION OF UNSATURATED CONJUGATED KETONES WITH SODIUM DITHIONITE UNDER PHASE TRANSFER CATALYSIS
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Selective double bond reduction of unsaturated conjugated ketones has been achieved in excellent yields by use of sodium dithionite in a two phase benzene-water system with Adogen as phase transfer catalyst.However, this reduction was unsatisfactory for hydrophilic ketones; in this case, competitive reactions led to the predominant formation of water soluble sulfur derivatives, similar to those obtained in the reaction of unsaturated conjugated ketones with sodium dithionite in aqueous dimethylformamide.
- Camps, Francisco,Coll, Jose,Guitart, Josefa
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- ULTRASONICALLY IMPROVED REDUCTIVE PROPERTIES OF AN AQUEOUS Zn-NiCl2 SYSTEM - 2. REGIOSELECTIVITY IN THE REDUCTION OF (-)-CARVONE
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While the previously described reductive system Zn-NiCl2 leads to the non-selective hydrogenation of the two olefinic bonds of (-)-carvone 1, the two selective hydrogenation products (+)-dihydrocarvone 2 and carvotaneacetone 3 are obtained in good yield with the same reagent under modified experimental conditions.
- Petrier, Christian,Luche, Jean-Louis
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- Asymmetric reduction of (4R)-(-)-carvone catalyzed by Baker's yeast in aqueous mono- and biphasic systems
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(1R,4R)-dihydrocarvone (2), an important renewable building block, was prepared with good conversions and excellent diastereoisomeric excess through the reduction of the α,β-unsatured carbon-carbon double bond of (4R)-(-)-carvone (1) mediated by Baker's yeast (BY) in aqueous mono- and biphasic systems. Some parameters that may alter this bioreduction reaction, such as the concentrations of yeast and substrate, temperature, and pH, were evaluated. The effect of the addition of different additives on the course of 1 biotransformation was also investigated. The results showed that the conversion and diastereoisomeric excesses were strongly dependent on these variables. The optimum reaction conditions were 100 g L-1 of BY, 16.6 mM of substrate, and pH 7.5 at 26 °C in the presence of DMSO, trehalose, or sucrose as additives. Under the optimum conditions, the (1R,4R)-dihydrocarvone was recovered with diastereoisomeric excesses of 92-99% and with conversions of 70-74%.
- Silva, Vanessa Dutra,Stambuk, Boris Ugarte,Nascimento, Maria Da Graa
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- Novel concurrent redox cascades of (R)- and (S)-carvones enables access to carvo-lactones with distinct regio- and enantioselectivity
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Within this study, we investigated a one-pot enzymatic redox cascade composed of different enoate reductases (5 EREDs from diverse bacterial origins) and various Baeyer-Villiger monooxygenases (4 BVMOs) with complementary regioselectivity that enabled access to six out of eight carvo-lactone stereoisomers starting from readily available natural carvones. Applicability of this two-step cascade was demonstrated by preparative scale experiments yielding up to 76% of the desired chiral carvolactone.
- Iqbal, Naseem,Stewart, Jon D.,Macheroux, Peter,Rudroff, Florian,Mihovilovic, Marko D.
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- Conjugate reduction of α,β-unsaturated ketones using an Mn(III) catalyst, phenylsilane and isopropyl alcohol
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Treatment of a variety of α,β-unsaturated ketones with Mn(dpm)3 (3 mol%)/PhSiH3 (1.3 equiv.)/isopropyl alcohol with the exclusion of air resulted in the formation of the saturated ketone. (C) 2000 Elsevier Science Ltd.
- Magnus,Waring,Scott
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- C3 and C6 Modification-Specific OYE Biotransformations of Synthetic Carvones and Sequential BVMO Chemoenzymatic Synthesis of Chiral Caprolactones
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The scope for biocatalytic modification of non-native carvone derivatives for speciality intermediates has hitherto been limited. Additionally, caprolactones are important feedstocks with diverse applications in the polymer industry and new non-native terpenone-derived biocatalytic caprolactone syntheses are thus of potential value for industrial biocatalytic materials applications. Biocatalytic reduction of synthetic analogues of R-(?)-carvone with additional substituents at C3 or C6, or both C3 and C6, using three types of OYEs (OYE2, PETNR and OYE3) shows significant impact of both regio-substitution and the substrate diastereomer. Bioreduction of (?)-carvone derivatives substituted with a Me and/or OH group at C6 is highly dependent on the diastereomer of the substrate. Derivatives bearing C6 substituents larger than methyl moieties are not substrates. Computer docking studies of PETNR with both (6S)-Me and (6R)-Me substituted (?)-carvone provides a model consistent with the outcomes of bioconversion. The products of bioreduction were efficiently biotransformed by the Baeyer–Villiger monooxygenase (BVase) CHMO_Phi1 to afford novel trisubstituted lactones with complete regioselectivity to provide a new biocatalytic entry to these chiral caprolactones. This provides both new non-native polymerization feedstock chemicals, but also with enhanced efficiency and selectivity over native (+)-dihydrocarvone Baeyer–Villigerase expansion. Optimum enzymatic reactions were scaled up to 60–100 mg, demonstrating the utility for preparative biocatalytic synthesis of both new synthetic scaffold-modified dihydrocarvones and efficient biocatalytic entry to new chiral caprolactones, which are potential single-isomer chiral polymer feedstocks.
- Issa, Issa S.,Toogood, Helen S.,Johannissen, Linus O.,Raftery, James,Scrutton, Nigel S.,Gardiner, John M.
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- Total Synthesis of (?)-Rotundone and (?)-epi-Rotundone from Monoterpene Precursors
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The first total synthesis of (?)-rotundone has been accomplished from (+)-(R)-limonene and therefore for the first time from an unrelated monoterpene instead of modifying structurally closely related sesquiterpene precursors such as α-guaiene. Challenges such as intermediates with stereocenters prone to epimerization by enolization were overcome by designing a β-methyl-keto route starting from (+)-(R)-limonene which finally gave (?)-rotundone by Nazarov cyclization of a precursor 13a. Diastereomer (?)-epi-rotundone was separated from (?)-rotundone chromatographically. An alternative route from rac-citronellal provided a diastereomer mixture of racemic Nazarov precursor 13 through a TRIP-catalyzed intramolecular aldolization, thus indicating that the Nazarov cyclization precursor 13a is in principle accessible from (?)-(S)-citronellal. The 11-step synthesis from (+)-(R)-limonene with ca. 1 % overall yield confirmed the absolute configuration of (?)-rotundone and provided samples of good olfactory quality.
- Rüthi, Fabian,Schr?der, Fridtjof
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- (R)-(-)-carvone and (1R, 4R)-trans-(+)-dihydrocarvone from Poiretia latifolia vogel
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The essential oils of Poiretia latifolia Vogel, native and cultivated leaves (Samples A and B, respectively) and native flowers (sample C), were obtained by hydrodistillation and analyzed by GC, GC/MS and chiral phase gas chromatography (CPGC). Twenty-four compounds were identified, representing 99.25, 99.26 and 99.23percent of the oils, respectively. The major constituents of the oils were the monoterpenes (S)-(-)-limonene (16.05, 27.60, 15.60percent, respectively), (1R, 4R)-trans-(+)-dihydrocarvone (18.05, 0.66 and 77.80percent, respectively) and (R)-(-)-carvone (61.05, 64.20 and 4.50percent, respectively). The essential oils were evaluated against some strains of Gram (+) and Gram (-) bacteria, and yeast, but displayed only modest antimicrobial activity.
- Porto, Carla,Stu?ker, Caroline Z.,Mallmann, Anderson S.,Simionatto, Euclesio,Flach, Adriana,Do Canto-Dorow, Tais,Da Silva, Ubiratan F.,Dalcol, Ionara I.,Morel, Ademir F.
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- Molybdenum(II) Complexes with α-Diimines: Catalytic Activity in Organic and Ionic Liquid Solvents
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The new [MoX(η3-C3H5)(CO)2(α-diimine)] complexes with: (i) X = Br or triflate and α-diimine = 1,10-phenanthroline (phen) and dipyridophenazine (dppz); and (ii) X = Br and α-diimine = phen and dppz, with several substituents, are synthesized and characterized. The structures of [MoBr(η3-C3H5)(CO)2(Cl-phen)] and [Mo(CF3SO3)(η3-C3H5)(CO)2(dppz)] are determined by using single-crystal X-ray diffraction. These and three complexes of 2,2′-bipyridyl (bpy), and its two derivatives with Me and tBu substituents, are tested in the homogeneous catalytic epoxidation of several olefins in dichloromethane, exhibiting, in general, a good selectivity towards the respective epoxide and relatively low TOFs. For the first time, the oxidation of cis-cyclooctene with some of these catalysts is also conducted in a variety of room-temperature ionic liquids (RTILs). In the presence of [MoBr(η3-C3H5)(CO)2(phen)], the conversions, in general, increase, compared with the reactions in organic solvents. Interestingly, different chemoselectivity is found when [C6mim][Ntf2] and [C2mim][FAP] are used with diol (24–26 %). On the other hand, [MoBr(η3-C3H5)(CO)2(L)] (L = Me-phen or dppz) exhibits much lower conversions in the RTILs tested than in common organic solvents.
- Saraiva, Marta S.,Nunes, Carla D.,Félix, Vítor,Ribeiro, Ana P. C.,de Castro, Carlos Nieto,Calhorda, Maria José
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- Selective Catalytic Synthesis of 1,2- and 8,9-Cyclic Limonene Carbonates as Versatile Building Blocks for Novel Hydroxyurethanes
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The selective catalytic synthesis of limonene-derived monofunctional cyclic carbonates and their subsequent functionalisation via thiol–ene addition and amine ring-opening is reported. A phosphotungstate polyoxometalate catalyst used for limonene epoxidation in the 1,2-position is shown to also be active in cyclic carbonate synthesis, allowing a two-step, one-pot synthesis without intermittent epoxide isolation. When used in conjunction with a classical halide catalyst, the polyoxometalate increased the rate of carbonation in a synergistic double-activation of both substrates. The cis isomer is shown to be responsible for incomplete conversion and by-product formation in commercial mixtures of 1,2-limomene oxide. Carbonation of 8,9-limonene epoxide furnished the 8,9-limonene carbonate for the first time. Both cyclic carbonates underwent thiol–ene addition reactions to yield linked di-monocarbonates, which can be used in linear non-isocyanate polyurethanes synthesis, as shown by their facile ring-opening with N-hexylamine. Thus, the selective catalytic route to monofunctional limonene carbonates gives straightforward access to monomers for novel bio-based polymers.
- Maltby, Katarzyna A.,Hutchby, Marc,Plucinski, Pawel,Davidson, Matthew G.,Hintermair, Ulrich
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- STEREOSELECTIVITY OF THE REDUCTION OF CARVONE AND DIHYDROCARVONE BY SUSPENSION CELLS OF NICOTIANA TABACUM
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The biotransformation of foreign substrates with suspension cells of Nicotiana tabacum was tested with (4R)-(-)- and (4S)-(+)-carvones, (1R,4R)-(+)- and (1S,4S)-(-)-dihydrocarvones and (1S,4R)-(+)- and (1R,4S)-(-)-isodihydrocarvones.It was found that the cells reduced regio- and stereoselectively the C-C double bond adjacent to the carbonyl group from the si-face and then the carbonyl group from the re-face, leaving the C-C double bond in the 1-methylethenyl group unattacked. - Key Word Index - Nicotiana tabacum; Solanaceae; tissue culture; biotransformation; stereoselective reduction; carvone; dihydrocarvone; isodihydrocarvone.
- Hirata, Toshifumi,Hamada, Hiroki,Aoki, Tadashi,Suga, Takayuki
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- Acidity and Catalytic Activity of Iron(II) Sulfate Heat-treated at High Temperatures
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Acidity and catalytic activity of FeSO4 calcined at 500-900 deg C were studied.The product obtained by calcination at 700 deg C showed maximum acidity at Ho1.5 and activity for isomerization of d-limonene oxide, polymerization of isobutyl vinyl ether and dehydration of 2-propanol.When calcined at 750 deg C the product showed no acidity or activity.
- Arata, Kazushi,Hino, Makoto
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- Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
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Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch.
- Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
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supporting information
p. 21176 - 21182
(2020/09/17)
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- Synthesis and Biochemical Evaluation of Nicotinamide Derivatives as NADH Analogue Coenzymes in Ene Reductase
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Nicotinamide and pyridine-containing conjugates have attracted a lot of attention in research as they have found use in a wide range of applications including as redox flow batteries and calcium channel blockers, in biocatalysis, and in metabolism. The interesting redox character of the compounds’ pyridine/dihydropyridine system allows them to possess very similar characteristics to the natural chiral redox agents NAD+/NADH, even mimicking their functions. There has been considerable interest in designing and synthesizing NAD+/NADH mimetics with similar redox properties. In this research, three nicotinamide conjugates were designed, synthesized, and characterized. Molecular structures obtained through X-ray crystallography were obtained for two of the conjugates, thereby providing more detail on the bonding and structure of the compounds. The compounds were then further evaluated for biochemical properties, and it was found that one of the conjugates possessed similar functions and characteristics to the natural NADH. This compound was evaluated in the active enzyme, enoate reductase; like NADH, it was shown to help reduce the C=C double bond of three substrates and even outperformed the natural coenzyme. Kinetic data are reported.
- Falcone, Natashya,She, Zhe,Syed, Jebreil,Lough, Alan,Kraatz, Heinz-Bernhard
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p. 838 - 845
(2019/02/07)
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- Buagafuran Active Pharmaceutical Ingredient, Preparation Method and Application Thereof
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A method suitable for large-scale production of buagafuran active pharmaceutical ingredient. A buagafuran active pharmaceutical ingredient (API) with a high purity prepared by the method includes an active ingredient of buagafuran, an impurity A, and an i
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Paragraph 0031-0032
(2019/11/21)
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- Hydrogenation of Carbonyl Derivatives Catalysed by Manganese Complexes Bearing Bidentate Pyridinyl-Phosphine Ligands
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Manganese(I) catalysts incorporating readily available bidentate 2-aminopyridinyl-phosphine ligands achieve a high efficiency in the hydrogenation of carbonyl compounds, significantly better than parent ones based on more elaborated and expensive tridentate 2,6-(diaminopyridinyl)-diphosphine ligands. The reaction proceeds with low catalyst loading (0.5 mol%) under mild conditions (50 °C) with yields up to 96%. (Figure presented.).
- Wei, Duo,Bruneau-Voisine, Antoine,Chauvin, Téo,Dorcet, Vincent,Roisnel, Thierry,Valyaev, Dmitry A.,Lugan, No?l,Sortais, Jean-Baptiste
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supporting information
p. 676 - 681
(2017/12/26)
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- Enantio- A nd regioselective: Ene-reductions using F420H2-dependent enzymes
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In the past decade it has become clear that many microbes harbor enzymes that employ an unusual flavin cofactor, the F420 deazaflavin cofactor. Herein we show that F420-dependent reductases (FDRs) can successfully perform enantio-, regio- A nd chemoselective ene-reductions. For the first time, we have demonstrated that F420H2-driven reductases can be used as biocatalysts for the reduction of α,β-unsaturated ketones and aldehydes with good conversions (>99%) and excellent regioselectivities and enantiomeric excesses (>99% ee). Noteworthily, FDRs typically display an opposite enantioselectivity when compared to the well established FMN-dependent Old Yellow Enzymes (OYEs).
- Mathew, Sam,Trajkovic, Milos,Kumar, Hemant,Nguyen, Quoc-Thai,Fraaije, Marco W.
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supporting information
p. 11208 - 11211
(2018/10/15)
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- Investigating: Saccharomyces cerevisiae alkene reductase OYE 3 by substrate profiling, X-ray crystallography and computational methods
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Saccharomyces cerevisiae OYE 3 shares 80% sequence identity with the well-studied Saccharomyces pastorianus OYE 1; however, wild-type OYE 3 shows different stereoselectivities toward some alkene substrates. Site-saturation mutagenesis of Trp 116 in OYE 3 followed by substrate profiling showed that the mutations had relatively little effect, opposite to that observed previously for OYE 1. The X-ray crystal structures of unliganded and phenol-bound OYE 3 were solved to 1.8 and 1.9 ? resolution, respectively. Both structures were nearly identical to that of OYE 1, with only a single amino acid difference in the active site region (Ser 296 versus Phe 296, part of loop 6). Despite their essentially identical static X-ray structures, molecular dynamics (MD) simulations revealed that loop 6 conformations differed significantly in solution between OYE 3 and OYE 1. In OYE 3, loop 6 remained nearly as open as observed in the crystal structure; by contrast, loop 6 closed over the active site of OYE 1 by ca. 4 ?. Loop closure likely generates a greater number of active site protein contacts for substrate bound to OYE 1 as compared to OYE 3. These differences provide an explanation for the differing stereoselectivities of OYE 3 and OYE 1, despite their nearly identical X-ray crystal structures.
- Powell, Robert W.,Buteler, M. Pilar,Lenka, Sunidhi,Crotti, Michele,Santangelo, Sara,Burg, Matthew J.,Bruner, Steven,Brenna, Elisabetta,Roitberg, Adrian E.,Stewart, Jon D.
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p. 5003 - 5016
(2018/10/17)
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- Transfer hydrogenation of ketones catalyzed by iridium-bulky phosphine complexes
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The complexes [Ir(COD)(PR3)2]PF6 (R = PPh3 (1); R = PBn3 = tribenzylphosphine (2)), [Ir(COD)(PBn3)(PAn3)]PF6 (3) (PAn3 = Tri-orthoanisyl-phosphine) and cis-(P,P)-[IrH(COD)(PBn3){η2-P,C-(C6H4CH2)PBn2}]PF6 (4) are active in the transfer hydrogenation of ketones. However, complex (3) gives the best results in conversion toward the alcohol. Interestingly, commercial isopropanol was used as hydrogen source, without any drying treatment. In situ generated isopropoxide was used as base. An efficient conversion of a variety of ketones, aromatic or aliphatic, cyclic or linear, including molecules with conjugated or isolated C[dbnd]C moieties was achieved, thus reporting 12 examples of hydrogenated substrates. Ketones of higher steric hindrance could not be converted under the studied conditions. The experimental evidence indicates that the steric and electronic properties of the substrates are determinant in the observed conversions and performance of the system. For α,β-unsaturated ketones, preference toward the reduction of the C[dbnd]C bond was observed. However, the system shows chemoselectivity toward the carbonyl group in molecules which also bear an isolated C[dbnd]C moiety. With the results obtained, a pseudo first-order dependence of the reaction rate on the concentration of ketone was determined. Also, stoichiometric as well as in situ tests were performed to shed light into the reaction pathways possibly involved in the catalytic TH of ketones described herein (precursor 3, base and isopropyl alcohol as hydrogen source).
- Landaeta, Vanessa R.,Rosa, Abel D. Salazar-La,Rodríguez-Lugo, Rafael E.
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p. 303 - 311
(2017/09/06)
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- Selective one-pot carvone oxime hydrogenation over titania supported gold catalyst as a novel approach for dihydrocarvone synthesis
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It was shown for the first time that dihydrocarvone can be selectively produced by gold-catalyzed one-pot transformation of carvone oxime. This reaction was carried out at 100 °C under hydrogen pressure of 9 bar over 1.9 wt.% Au/TiO2 catalyst using methanol as a solvent. Dihydrocarvone synthesis was shown to occur via carvone formation with the subsequent hydrogenation of its conjugated C=C double bond. Application of Au/TiO2 catalyst for both deoximation and selective hydrogenation of olefinic C=C functional group is reported for the first time. The combination of these steps provides optimization of the synthetic method for dihydrocarvone production from carvone oxime which is a key intermediate in carvone synthesis from limonene. Despite a lower reaction rate than in the case of carvone, a significant increase in the stereoselectivity towards trans-dihydrocarvone was observed in the case of carvone oxime hydrogenation. The ratio between trans- and cis-dihydrocarvone was close to 4.0 compared to 1.8 achieved in the case of carvone hydrogenation.
- Demidova, Yu. S.,Suslov,Simakova,Volcho,Salakhutdinov,Simakova,Murzin, D. Yu.
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p. 142 - 148
(2016/06/13)
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- Cell-free protein engineering of Old Yellow Enzyme 1 from Saccharomyces pastorianus
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In protein engineering, cell-free transcription/translation of linear mutagenic DNA templates can tremendously accelerate and simplify the screening of enzyme variants. Using the RApid Parallel Protein EvaluatoR (RAPPER) protocol, we have evaluated the impact of amino acid substitutions and loop truncations on substrate specificity and stereoselectivity of Old Yellow Enzyme 1 from Saccharomyces pastorianus. Our study demonstrates the benefit of systematically assessing amino acid variations including substrate profiling to explore sequence-function space.
- Quertinmont, Leann T.,Lutz, Stefan
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p. 7282 - 7287
(2016/10/29)
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- New biobased tetrabutylphosphonium ionic liquids: Synthesis, characterization and use as a solvent or co-solvent for mild and greener Pd-catalyzed hydrogenation processes
-
Phosphonium-based Ionic Liquids (PhosILs) with natural organic derived anions (l-lactate, l-tartrate, malonate, succinate, l-malate, pyruvate, d-glucuronate, d-galacturonate, ferulate, p-coumarate) were easily prepared by acid-base method from tetrabutylphosphonium hydroxide and an excess of the corresponding acid with good yields. Their characterization was realized through classical NMR, IR and elemental analysis techniques; their viscosity and ATG parameters were also determined. These ionic liquids showed good performance and recyclability in the selective Pd-catalyzed hydrogenation of alkenes, polyenes like linoleic acid and enantioselective hydrogenation of unsaturated ketones such as isophorone at room temperature under atmospheric H2 pressure. Furthermore, NMR studies leading to computational calculations were performed to establish easily the composition of the resulting mixture obtained through the hydrogenation of linoleic acid.
- Hayouni, Safa,Robert, Anthony,Ferlin, Nadège,Amri, Hassen,Bouquillon, Sandrine
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p. 113583 - 113595
(2016/12/16)
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- Ene Reductase Enzymes for the Aromatisation of Tetralones and Cyclohexenones to Naphthols and Phenols
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Ene reductases (EREDs) have great potential as oxidation biocatalysts, as demonstrated by their efficient conversion of a number of tetralones to the corresponding naphthols. Of 96 enzymes tested, 57 were able to produce 2-naphthol in this way. Further tests with substituted tetralones revealed typically high conversions up to >99%. The reactions were performed under mild conditions in aqueous buffer with only co-solvent, biocatalyst and oxidation substrate required for conversion. Production of a methoxy-substituted naphthol was also successfully performed on a gram scale, with 91% yield. This methodology provides a new avenue to produce substituted naphthols as valuable building blocks, with the possibility to extend the approach to the production of phenols also being demonstrated.
- Kelly, Paul P.,Lipscomb, David,Quinn, Derek J.,Lemon, Ken,Caswell, Jill,Spratt, Jenny,Kosjek, Birgit,Truppo, Matthew,Moody, Thomas S.
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supporting information
p. 731 - 736
(2016/03/09)
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- Method for synthesizing dihydrocarvone by use of epoxy limonene
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The invention discloses a method for synthesizing dihydrocarvone by use of epoxy limonene. The method comprises the following steps: step 1, mixing epoxy limonene with a main catalyst A or an aided catalyst B, and heating to trigger a ring-opening rearrangement reaction, so as to generate dihydrocarvone; step 2, after the reaction is finished, adding white oil into the reaction liquid, and carrying out rectification to obtain a finished product of dihydrocarvone, wherein the main catalyst A is divalent-zinc lewis acid, and the aided catalyst B comprises one or two of organic alkali, ester or acyl ketone compounds. The method has the following advantages: the raw materials are easy to synthesize, cheap, and easy to obtain; no solvent is needed in the reaction process, so that the synthesis technology is environmentally friendly; post-processing purification can be achieved only through rectification, therefore the post-processing purification technology is simple; the selected catalyst can be recycled, and the method is suitable for industrialized production.
- -
-
Paragraph 0018
(2016/11/09)
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- Structural insights into stereospecific reduction of α, β-unsaturated carbonyl substrates by old yellow enzyme from Gluconobacter oxydans
-
We report the crystal structure of old yellow enzyme (OYE) family protein Gox0502 (a.a 1-315) in free form at 3.3 ?. Detailed structural analysis revealed the key residues involved in stereospecific determination of Gox0502, such as Trp66 and Trp100. Structure-based computational analysis suggested the bulky side chains of these tryptophan residues may play important roles in product stereoselectivity. The introduction of Ile or Phe or Tyr mutation significantly reduced the product diastereoselectivity. We hypothesized that less bulky side chains at these critical residues could create additional free space to accommodate intermediates with different conformations. Notably, the introduction of Phe mutation at residue Trp100 increased catalytic activity compared to wild-type Gox0502 toward a set of substrates tested, which suggests that a less bulky Phe side chain at residue W100F may facilitate product release. Therefore, Gox0502 structure could provide useful information to generate desirable OYEs suitable for biotechnological applications in industry.
- Yin, Bo,Deng, Jian,Lim, Lirong,Yuan, Y. Adam,Wei, Dongzhi
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p. 410 - 421
(2015/08/11)
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- A Rapid and High-Throughput Assay for the Estimation of Conversions of Ene-Reductase-Catalysed Reactions
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A fast and sensitive colorimetric assay (FRED, fast and reliable ene-reductases detection) that allows the estimation of levels of conversion of ene-reductase (ER)-catalysed reactions has been developed. The activated olefin is reduced by ER at the expense of NAD(P)H cofactor, whose regeneration is carried out in situ by the glucose/glucose dehydrogenase system. Subsequently, the consumption of the co-substrate glucose is determined colorimetrically by a multienzymatic system. The FRED assay offers a wide range of possible applications, from enzyme fingerprinting and kinetic analysis, to primary screening of enzyme libraries and optimisation of ERs' performances under different reaction conditions.
- Forchin, Maria Chiara,Crotti, Michele,Gatti, Francesco G.,Parmeggiani, Fabio,Brenna, Elisabetta,Monti, Daniela
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p. 1571 - 1573
(2015/07/27)
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- Palladium on charcoal as a catalyst for stoichiometric chemo- and stereoselective hydrosilylations and hydrogenations with triethylsilane
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Stoichiometric quantities of triethylsilane in the presence of activated Pd/C as the catalyst can be used to effect chemo-, regio-, and stereoselective hydrosilylation and transfer hydrogenation reactions. α,β-Unsaturated aldehydes and ketones are selectively hydrosilylated to give the corresponding enol silanes or transfer hydrogenated to give the saturated carbonyl compounds in the presence of other reducible functional groups.
- Tuokko, Sakari,Pihko, Petri M.
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p. 1740 - 1751
(2015/02/19)
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- Regioselective mono-deprotection of di-ferf-butylsilylene acetal derived from 1,3-diol with ammonium fluoride
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Here we report a novel and efficient method for the regioselective mono-deprotection of di-terf-butylsilylene acetals derived from 1,3-diols consisting of primary and secondary alcohols. The ammonium fluoride-mediated reactions of pyripyropene A derivative, thymidine and uridine derivatives, methyl β-D-glucofuranoside, and pyranoside derivatives each gave the corresponding primary alcohol with high regioselectivity.
- Ohtawa, Masaki,Tomoda, Hiroshi,Nagamitsu, Tohru
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supporting information
p. 113 - 118
(2014/02/14)
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- Pichia stipitis OYE 2.6 variants with improved catalytic efficiencies from site-saturation mutagenesis libraries
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An earlier directed evolution project using alkene reductase OYE 2.6 from Pichia stipitis yielded 13 active site variants with improved properties toward three homologous Baylis-Hillman adducts. Here, we probed the generality of these improvements by testing the wild-type and all 13 variants against a panel of 16 structurally-diverse electron-deficient alkenes. Several substrates were sterically demanding, and as hoped, creating additional active site volume yielded better conversions for these alkenes. The most impressive improvement was found for 2-butylidenecyclohexanone. The wild-type provided less than 20% conversion after 24 h; a triple mutant afforded more than 60% conversion in the same time period. Moreover, even wild-type OYE 2.6 can reduce cyclohexenones with very bulky 4-substituents efficiently.
- Patterson-Orazem, Athéna,Sullivan, Bradford,Stewart, Jon D.
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p. 5628 - 5632
(2015/01/09)
-
- Production of flavours and fragrances via bioreduction of (4R)-(-)-carvone and (1R)-(-)-myrtenal by non-conventional yeast whole-cells
-
As part of a program aiming at the selection of yeast strains which might be of interest as sources of natural flavours and fragrances, the bioreduction of (4R)-(-)-carvone and (1R)-(-)-myrtenal by whole-cells of non-conventional yeasts (NCYs) belonging to the genera Candida, Cryptococcus, Debaryomyces, Hanseniaspora, Kazachstania, Kluyveromyces, Lindnera, Nakaseomyces, Vanderwaltozyma and Wickerhamomyces was studied. Volatiles produced were sampled by means of headspace solid-phase microextraction (SPME) and the compounds were analysed and identified by gas chromatography-mass spectroscopy (GC-MS). Yields (expressed as % of biotransformation) varied in dependence of the strain. The reduction of both (4R)-(-)-carvone and (1R)-(-)-myrtenal were catalyzed by some ene-reductases (ERs) and/or carbonyl reductases (CRs), which determined the formation of (1R,4R)-dihydrocarvone and (1R)-myrtenol respectively, as main flavouring products. The potential of NCYs as novel whole-cell biocatalysts for selective biotransformation of electron-poor alkenes for producing flavours and fragrances of industrial interest is discussed.
- Goretti, Marta,Turchetti, Benedetta,Cramarossa, Maria Rita,Forti, Luca,Buzzini, Pietro
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p. 5736 - 5748
(2013/07/19)
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- Mimicking nature: Synthetic nicotinamide cofactors for C=C bioreduction using enoate reductases
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A series of synthetic nicotinamide cofactors were synthesized to replace natural nicotinamide cofactors and promote enoate reductase (ER) catalyzed reactions without compromising the activity or stereoselectivity of the bioreduction process. Conversions and enantioselectivities of >99% were obtained for C=C bioreductions, and the process was successfully upscaled. Furthermore, high chemoselectivity was observed when employing these nicotinamide cofactor mimics (mNADs) with crude extracts in ER-catalyzed reactions.
- Paul, Caroline E.,Gargiulo, Serena,Opperman, Diederik J.,Lavandera, Iván,Gotor-Fernández, Vicente,Gotor, Vicente,Taglieber, Andreas,Arends, Isabel W. C. E.,Hollmann, Frank
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p. 180 - 183
(2013/04/24)
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- Heteropoly acid catalysts for the synthesis of fragrance compounds from biorenewables: Isomerization of limonene oxide
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The liquid-phase isomerization of limonene oxide was studied in the presence of heteropoly acid catalysts in aprotic solvents in homogeneous and heterogeneous systems. Among the catalysts were bulk and silica-supported tungstophosphoric acid H3PW12O40 and its acidic Cs salt Cs0.5H0.5PW12O40 (CsPW). The reaction gave dihydrocarvone, a valuable fragrance intermediate, as the main product with turnover numbers of up to 8000. The nature of the solvent had a strong effect on reaction rate and selectivity. CsPW (0.1 mol%) was found to be a highly efficient and truly heterogeneous catalyst for this reaction, providing 82% yield of dihydrocarvone in 1,4-dioxane as a solvent under ambient conditions. This simple catalytic method represents economically attractive route to industrially important compounds starting from bio-renewable substrates easily available from essential oils. The Royal Society of Chemistry 2013.
- Costa, Vinicius V.,Da Silva Rocha, Kelly A.,Kozhevnikov, Ivan V.,Kozhevnikova, Elena F.,Gusevskaya, Elena V.
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p. 244 - 250
(2013/04/10)
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- A base-promoted deprotection of 1,3-dioxolanes to ketones
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An effective deprotection methodology of dioxolanes was developed, affording moderate to excellent yield via a LTMP-promoted reaction in THF, which displays admirable chemoselectivity in the presence of dimethylketal, 1,3-dioxane, 1,3-dithiane, or other acid-sensitive protective groups.
- Yuan, Changchun,Yang, Li,Yue, Guizhou,Yu, Tianzi,Zhong, Weiming,Liu, Bo
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supporting information
p. 6972 - 6976
(2013/01/15)
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- Use of immobilized transition metal complexes as recyclable catalysts for oxidation reactions with hydrogen peroxide as oxidant
-
A tetradentate Schiff base (teta), obtained from triethylenetetramine and salicylaldehyde, has been covalently bonded to divinylbenzene cross-linked chloromethylated polystyrene. This chelating ligand, abbreviated as PS-teta (PS = polymeric support), reacts with metal chlorides (Cu2+, Co 2+, and Ni2+) in methanol to give polymerbound transition metal complexes, PS-Cu(II)teta/(Cat-1), PS-Ni(II)teta/(Cat-2), and PS-Co(II)teta/(Cat-3), formation of which has been established by various physiochemical methods and spectroscopic techniques. The catalytic potential of these materials has been tested for the oxidation of various alkenes, alkanes, alcohols, and thioethers in the presence of 30% H2O2 as an oxidant. At the same time, these catalysts are very stable and could be reused in oxidation reactions for more than five times without noticeable loss of their catalytic activity. Springer Science+Business Media B.V. 2011.
- Islam, Sk Manirul,Mobarok, Manir,Mondal, Paramita,Roy, Anupam Singha,Salam, Noor,Hossain, Dildar,Mondal, Sanchita
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experimental part
p. 97 - 107
(2012/09/22)
-
- A Site-Saturated Mutagenesis Study of Pentaerythritol Tetranitrate Reductase Reveals that Residues 181 and 184 Influence Ligand Binding, Stereochemistry and Reactivity
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We have conducted a site-specific saturation mutagenesis study of H181 and H184 of flavoprotein pentaerythritol tetranitrate reductase (PETN reductase) to probe the role of these residues in substrate binding and catalysis with a variety of α,β-unsaturated alkenes. Single mutations at these residues were sufficient to dramatically increase the enantiopurity of products formed by reduction of 2-phenyl-1-nitropropene. In addition, many mutants exhibited a switch in reactivity to predominantly catalyse nitro reduction, as opposed to C=C reduction. These mutants showed an enhancement in a minor side reaction and formed 2-phenylpropanal oxime from 2-phenyl-1-nitropropene. The multiple binding conformations of hydroxy substituted nitro-olefins in PETN reductase were examined by using both structural and catalytic techniques. These compounds were found to bind in both active and inhibitory complexes; this highlights the plasticity of the active site and the ability of the H181/H184 couple to coordinate with multiple functional groups. These properties demonstrate the potential to use PETN reductase as a scaffold in the development of industrially useful biocatalysts. Divergent evolution: A site-saturation study of PETN reductase was performed at conserved substrate binding residues H181 and H184. These residues were shown to dramatically alter the ratio of alkene versus nitro-group reduction in favour of oxime by-product formation, as summarised in the picture.
- Toogood, Helen S.,Fryszkowska, Anna,Hulley, Martyn,Sakuma, Michiyo,Mansell, David,Stephens, Gill M.,Gardiner, John M.,Scrutton, Nigel S.
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scheme or table
p. 738 - 749
(2012/02/01)
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- Structural influence on radical formation and sensitizing capacity of alkylic limonene hydroperoxide analogues in allergic contact dermatitis
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Hydroperoxides are known to be strong contact allergens and a common cause of contact allergy. They are easily formed by the autoxidation of, for example, fragrance terpenes, compounds that are common in perfumes, cosmetics, and household products. A requirement of the immunological mechanisms of contact allergy is the formation of an immunogenic hapten-protein complex. For hydroperoxides, a radical mechanism is postulated for this formation. In our previous investigations of allylic limonene hydroperoxides, we found that the formation of carbon-and oxygen-centered radicals, as well as the sensitizing capacity, is influenced by the structure of the hydroperoxides. The aim of the present work was to further investigate the connection between structure, radical formation, and sensitizing capacity by studying alkylic analogues of the previously investigated allylic limonene hydroperoxides. The radical formation was studied in radical-trapping experiments employing 5,10,15,20-tetraphenyl- 21H,23H-porphine iron(III) chloride as an initiator and 1,1,3,3- tetramethylisoindolin-2-yloxyl as a radical trapper. We found that the investigated hydroperoxides initially form carbon-and oxygen-centered radicals that subsequently form alcohols and ketones. Trapped carbon-centered radicals and nonradical products were isolated and identified. Small changes in structure, like the omission of the endocyclic double bond or the addition of a methyl group, resulted in large differences in radical formation. The results indicate that alkoxyl radicals seem to be more important than carbon-centered radicals in the immunogenic complex formation. The sensitizing capacities were studied in the murine local lymph node assay (LLNA), and all hydroperoxides tested were found to be potent sensitizers. For two of the hydroperoxides investigated, the recently suggested thiol-ene reaction is a possible mechanism for the formation of immunogenic complexes. For the third investigated, fully saturated, hydroperoxide, the thiol-ene mechanism is not possible for immunogenic complex formation. This strongly indicates that several radical reaction pathways for immunogenic complex formation of limonene hydroperoxides are active in parallel.
- Johansson, Staffan G. H.,Emilsson, Katarina,Grotli, Morten,Boerje, Anna
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experimental part
p. 677 - 688
(2011/02/24)
-
- Discovery of CP-690,550: A potent and selective janus kinase (JAK) inhibitor for the treatment of autoimmune diseases and organ transplant rejection
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There is a critical need for safer and more convenient treatments for organ transplant rejection and autoimmune disorders such as rheumatoid arthritis. Janus tyrosine kinases (JAK1, JAK3) are expressed in lymphoid cells and are involved in the signaling of multiple cytokines important for various T cell functions. Blockade of the JAK1/JAK3-STAT pathway with a small molecule was anticipated to provide therapeutic immunosuppression/immunomodulation. The Pfizer compound library was screened against the catalytic domain of JAK3 resulting in the identification of a pyrrolopyrimidine-based series of inhibitors represented by CP-352,664 (2a). Synthetic analogues of 2a were screened against the JAK enzymes and evaluated in an IL-2 induced T cell blast proliferation assay. Select compounds were evaluated in rodent efficacy models of allograft rejection and destructive inflammatory arthritis. Optimization within this chemical series led to identification of CP-690,550 1, a potential first-in-class JAK inhibitor for treatment of autoimmune diseases and organ transplant rejection.
- Flanagan, Mark E.,Blumenkopf, Todd A.,Brissette, William H.,Brown, Matthew F.,Casavant, Jeffrey M.,Shang-Poa, Chang,Doty, Jonathan L.,Elliott, Eileen A.,Fisher, Michael B.,Hines, Michael,Kent, Craig,Kudlacz, Elizabeth M.,Lillie, Brett M.,Magnuson, Kelly S.,McCurdy, Sandra P.,Munchhof, Michael J.,Perry, Bret D.,Sawyer, Perry S.,Strelevitz, Timothy J.,Subramanyam, Chakrapani,Sun, Jianmin,Whipple, David A.,Changelian, Paul S.
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experimental part
p. 8468 - 8484
(2011/02/26)
-
- pH-dependent catalytic activity and chemoselectivity in transfer hydrogenation catalyzed by iridium complex with 4,4′-dihydroxy-2,2′- bipyridine
-
Transfer hydrogenation catalyzed by an iridium catalyst with 4,4′dihydroxy-2,2′-bipyridine (DHBP) in an aqueous formate solution exhibits highly pH-dependent catalytic activity and chemoselectivity. The substantial change in the activity is due to the electronic effect based on the acid-base equilibrium of the phenolic hydroxyl group of DHBP. Under basic conditions, high turnover frequency values of the DHBP complex, which can be more than 1000 times the value of the unsubstituted analogue, are obtained (up to 81000 h-1 at 80°C). In addition, the DHBP catalyst exhibits pH-dependent chemoselectivity for α,β-unsaturated carbonyl compounds. Selective reduction of the C=C bond of enone with high activity are observed under basic conditions. The ketone moieties can be reduced with satisfactory activity under acidic conditions. In particular, pH-selective chemoselectivity of the C=O versus C=C bond reduction was observed in the transfer hydrogenation of cinnamaldehyde.
- Himeda, Yuichiro,Onozawa-Komatsuzaki, Nobuko,Miyazawa, Satoru,Sugihara, Hideki,Hirose, Takuji,Kasuga, Kazuyuki
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scheme or table
p. 11076 - 11081
(2009/11/30)
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- Acid-catalyzed reactions of sarcophytoxide, a marine cembranoid: An apparently enantio-directive reaction, unusual products and stereochemical reconsideration of epoxide-ketone rearrangement
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Perchloric acid treatment of sarcophytoxide, a marine cembranoid possessing an epoxide, brought about epoxide ketone rearrangement affording ketones. When the reaction time was long (22 h), a minor ketone that was antipodal to the ketone obtained in a short-time (l0min) reaction was formed. These puzzling findings, considering that the starting epoxide had three asymmetric carbons, were interpreted by surveying the structures of other ketonic products. The stereochemistry of a major ketone, which had been wrongly assigned, was corrected by extensive analyses of NMR spectra. The correct stereochemistry indicated that the epoxide-ketone rearrangement took a course via a cationic intermediate.
- Nii, Keiji,Tagami, Keiko,Rijima, Masaru,Munakata, Tatsuo,Ooi, Takashi,Kusumi, Takenori
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experimental part
p. 562 - 573
(2009/04/10)
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- Reduction of α, β-unsaturated ketones using a Zn/NiCl 2 system in aqueous media in the presence of anionic and cationic surfactants
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The reduction of aromatic and aliphatic α,β-unsaturated ketones, namely acetophenone (1) and (-)-carvone (3) with a Zn/NiCl2 system in H2O or H2O/EtOH media in the absence or presence of anionic and cationic surfactants have been investigated and have shown remarkable results. The anionic sodium dodecyl sulphate (SDS), the cationic cetyltrimethylammonium bromide (CTAB) and the non-micelle-forming didodecyldimethylammonium bromide (DDAB) surfactants were utilized. The reduction of acetophenone in H2O medium gave only a low yield of 1-phenyl ethanol (2) in comparison with the yields which resulted when a H 2O/EtOH medium was employed. The yields increased relatively in a H2O medium in the presence of cationic surfactants which showed a gradual increase at low concentrations following different patterns and sharp increases at 60 °C and pH9. The reduction of (-)-carvone (3) with the same system in H2O medium gave relatively higher yields than that of acetophenone. In the presence of cationic surfactants CTAB and DDAB in aqueous medium the total reduction yield increased appreciably and sometimes reached 100 % in the presence of DDAB at a concentration of 0.98 × 10-2 mol L-1 at 60 °C. The effects of pH, combined metallic salts and different surfactant concentrations on the reduction of (-)-carvone have been also investigated. This paper focuses on the application of surfactants in the reduction of α,β-enones by metal/metallic chloride/H2O systems in the absence of organic solvents. This method displays regioselectivity and stereoselectivity. This method may also be considered as a contribution to the antipollution process by means of the elimination of organic solvents from the chemical process.
- Ilikti, Hocine,Benabdallah, Tayeb,Bentayeb, Kamel,Othman, Adil A.,Derriche, Zoubir
-
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- Microbial Baeyer-Villiger oxidation of terpenones by recombinant whole-cell biocatalysts - Formation of enantiocomplementary regioisomeric lactones
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Recombinant whole-cell expression systems for Baeyer-Villiger monooxygenases of various bacterial origin were utilized in the regiodivergent biooxidation of cyclic terpenones enabling access to enantio- and regioisomeric lactones on preparative scale. This journal is The Royal Society of Chemistry.
- Ernuchova, Petra,Mihovilovic, Marko D.
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p. 1715 - 1719
(2008/02/10)
-
- Liquid-phase noncatalytic oxidation of monoterpenoids with nitrous oxide
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A series of monoterpenoids differing in the number of double bonds and the pattern of their substitution were tested in the liquid-phase noncatalytic oxidation with nitrous oxide (N2O). The structure of olefins has a significant effect on the oxidation route. In the case of terpenoids containing 1,1-disubstituted double bond, nor-carbonyl compounds are formed with high selectivity.
- Romanenko,Starokon',Panov,Tkacheva
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p. 1239 - 1243
(2008/09/17)
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- Daucus carota and baker's yeast mediated bio-reduction of prochiral ketones
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Stereoselective reduction of prochiral ketones to the corresponding alcohols using biocatalysts has attracted much attention, from the viewpoint of green chemistry. Asymmetric reduction of indanone, tetralone and hydroxyl trimonoterpene ketones to the corresponding enantiomerically pure (S)-alcohols, using Daucus carota plant homogenate and fermented baker's yeast cells, is described. The present study illustrates the broad substrate selectivity of the dehydrogenase enzymes present in the D. carota in the synthesis of a wide range of chiral secondary alcohols of biological importance.
- Yadav, Jhillu S.,Reddy, Garudammagari S.K.K.,Sabitha, Gowravaram,Krishna, Avvaru D.,Prasad, Attaluri R.,Hafeez-U-R-Rahaman,Vishwaswar Rao, Katta,Bhaskar Rao, Adari
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p. 717 - 723
(2008/02/02)
-
- Synthetic scope of alcohol transfer dehydrogenation catalyzed by Cu/Al 2O3: A new metallic catalyst with unusual selectivity
-
A method for the anaerobic oxidation of a wide series of alcohols including cyclohexanols and steroidal alcohols, has been set up. It relies on a transfer dehydrogenation reaction from the substrate alcohol to styrene catalyzed by a heterogeneous, reusable copper catalyst under very mild liquid phase experimental conditions (90°C, N2) and shows unusual selectivity. Thus, the method is selective for the oxidation of secondary and allylic alcohols even in the presence of unprotected primary and benzylic alcohols. Electronic effects and the choice of the hydrogen acceptor account for the selectivity observed.
- Zaccheria, Federica,Ravasio, Nicoletta,Psaro, Rinaldo,Fusi, Achille
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p. 6426 - 6431
(2008/09/20)
-
- A facile and chemoselective conjugate reduction using polymethylhydrosiloxane (PMHS) and catalytic B(C6F5) 3
-
A highly chemoselective conjugate reduction of electron-deficient Michael acceptors, including Α, β-unsaturated ketones, carboxylic esters, nitriles and nitro compounds with PMHS in the presence of catalytic B(C 6F5)3 was investigated. When attempts were made to improve the yields by increasing the amount of catalyst, the result was a complex mixture of saturated and unsaturated compounds, with partial reduction of the ketone moiety to the methylene functionality. PMHS along with a catalytic amount of B(C6F5)3 was found to be a unique reagent system for the conjugate reduction of Michael acceptors.
- Chandrasekhar, Srivari,Chandrashekar, Gudise,Reddy, Marepally Srinivasa,Srihari, Pabbaraja
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p. 1650 - 1652
(2008/02/03)
-
- A metal-free catalytic reduction of α,β-unsaturated carbonyl compounds with phenyldimethylsilane
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Selective reduction of α,β-unsaturated carbonyl compounds to the corresponding saturated ones by phenyldimethyl silane was promoted by a catalytic amount of I2O5 at ambient temperature in CH 2CI2.
- Mu, Ruizhu,Liu, Zhengang,Liu, Zhongquan,Yang, Li,Wu, Longmin,Liu, Zhong-Li
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p. 469 - 470
(2007/10/03)
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- Anaerobic oxidation of non-activated secondary alcohols over Cu/Al 2O3
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A liquid phase, transfer dehydrogenation reaction promoted by an 8% Cu/Al2O3 catalyst allows complete conversion of secondary alcohols into ketones under very mild conditions and in short times without any additives.
- Zaccheria, Federica,Ravasio, Nicoletta,Psaro, Rinaldo,Fusi, Achille
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p. 253 - 255
(2007/10/03)
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- Radical hydrometalation of functional ethylenic compounds: Radical autoinhibition changes the regioselectivity
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Hydrometalation of carbon-carbon double bonds by group 14 hydrides is inhibited by carbonyl compounds-mainly by α,β-unsaturated carbonyl groups-as efficiently as by classical radical trapping compounds, such as galvinoxyl and hydroquinone. This phenomenon
- El Kadib, Abdelkrim,Feddouli, Amal,Riviere, Pierre,Delpech, Fabien,Riviere-Baudet, Monique,Castel, Annie,Ahra, Mohamed,Hasnaoui, Aissa,Burgos, Francisco,Manriquez, Juan M.,Chavez, Ivone
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p. 446 - 454
(2008/10/09)
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- Asymmetric reduction of enones with Synechococcus sp. PCC 7942
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Synechococcus sp. PCC 7942, a cyanobacterium, reduced both the endocyclic C-C double bond of s-trans enones and the exocyclic C-C double bond of s-cis enones with high enantioselectivity to afford the corresponding (S)-ketones under illumination.
- Shimoda, Kei,Kubota, Naoji,Hamada, Hiroki,Kaji, Misato,Hirata, Toshifumi
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p. 1677 - 1679
(2007/10/03)
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