- A candidate cDNA clone for (-)-limonene-7-hydroxylase from Perilla frutescens
-
Cytochrome P450 mono-oxygenases from peppermint, spearmint and perilla (all members of the family Lamiaceae) mediate the regiospecific hydroxylation of the parent olefin (-)-limonene to produce essential oil components oxygenated at C3, C6 and C7, respectively. Cloning, expression and mutagenesis of cDNAs encoding the peppermint limonene-3-hydroxylase and the spearmint limonene-6-hydroxylase have allowed the identification of a single amino acid residue which determines the regiospecificity of oxygenation by these two enzymes. A hybridization strategy provided a cytochrome P450 limonene hydroxylase cDNA from perilla with which to further evaluate the structural determinants of regiospecificity for oxygenation of the common substrate (-)-limonene. The perilla cDNA was a partial clone of 1550 bp (lacking the N-terminal membrane insertion domain), and shared 66% identity with the peppermint 3-hydroxylase and spearmint 6-hydroxylase at the amino acid level. The perilla cytochrome P450 was expressed in Escherichia coli as a chimeric protein fused with the N-terminal membrane insertion domain of the limonene-3-hydroxylase. The kinetically competent recombinant protein was characterized and shown to produce a mixture of C3-, C6- and C7-hydroxylated limonene derivatives with a distribution of 33%, 14% and 53%, respectively.
- Mau, Christopher J.D.,Karp, Frank,Ito, Michiho,Honda, Gisho,Croteau, Rodney B.
-
-
Read Online
- Discovery and Engineering of Bacterial (?)-Isopiperitenol Dehydrogenases to Enhance (?)-Menthol Precursor Biosynthesis
-
Microbial synthesis of (?)-menthol, a compound of plant origin, is of great importance because of the high demand for this product and related sustainability issues. However, the total biosynthesis of (?)-menthol from easily available feedstocks like (?)-limonene by engineered microbial hosts is stalled by the poor protein expression or activity of several enzymes from the native (?)-menthol biosynthesis pathway of mint (Mentha piperita). Among these unsatisfied steps, (?)-isopiperitenol dehydrogenase (IPDH) catalyzed oxidation reaction of (?)-trans-isopiperitenol was one of the bottlenecks that need to be optimized. In this work, two novel bacterial enzymes with IPDH activity were discovered to replace their inefficient counterpart from plant cells in microbial (?)-menthol synthesis. Two key residues in PaIPDH from Pseudomonas aeruginosa were mutated to PaIPDHE95F/Y199V with 4.4-fold improved specific activity than PaIPDH. The mechanism for the beneficial mutations was elucidated by molecular dynamics simulations. PaIPDHE95F/Y199V was used to synthesize (?)-isopiperitenone from (?)-limonene in vivo via a self-sufficient cofactor cascade enzyme reaction, affording a 3.7-fold enhanced titer of (?)-isopiperitenone compared with that obtained using the original mint IPDH (MpIPDH). The bacterial enzyme PaIPDHE95F/Y199V can be applied in the future for constructing a more efficient artificial pathway to biosynthesize (?)-menthol in a microbial whole-cell system. (Figure presented.).
- Zhan, Jing-Ru,Shou, Chao,Zheng, Yu-Cong,Chen, Qi,Pan, Jiang,Li, Chun-Xiu,Xu, Jian-He
-
-
Read Online
- A study of some molecularly imprinted polymers as protic catalysts for the isomerisation of α-pinene oxide to trans-carveol
-
A range of acidic Molecularly Imprinted Polymers (MIPs) were synthesised using the imprint molecule trans-carvyl amine as a transition state analogue for the selective isomerisation of α-pinene oxide to trans-carveol. The amine functionality of the imprint molecule was used to selectively position a sulfonic acid group in the MIP binding pocket utilising 4-styrene sulfonic acid as the functional monomer. Co-polymerisation with varying ratios of styrene and divinylbenzene afforded a range of MIPs which were tested for their ability to effect selective formation of trans-carveol from α-pinene oxide. Although successful imprinting was demonstrated in binding studies, it was shown that solvent effects were dominant in effecting selective formation of trans-carveol. Using DMF as solvent, up to 70% of the products from acid catalysed isomerisation of α-pinene oxide with the polystyrene MIPs were obtained via the necessary para menthyl tertiary carbocation, and industrially important trans-carveol was obtained in 45% yield.
- Motherwell, William B.,Bingham, Matilda J.,Pothier, Julien,Six, Yvan
-
-
Read Online
- Isomerization of α-pinene oxide over cerium and tin catalysts: Selective synthesis of trans-carveol and trans-sobrerol
-
A remarkable effect of the solvent nature on the acid catalyzed transformation of α-pinene oxide allowed direction of the reaction to either trans-carveol or trans-sobrerol. Each of these highly valuable compounds was obtained in nearly 70% yield using an appropriate polar solvent, whose basicity affected strongly the product distribution. In acetone, a weakly basic solvent, the reaction over heterogeneous sol-gel Sn/SiO2 or Ce/SiO2 catalysts gave mainly trans-sobrerol. No leaching of active components occurs under the reaction conditions and the catalysts can be recovered and reused. On the other hand, in more basic solvent, i.e., dimethylacetamide, the reaction was essentially directed to trans-carveol. Due to the leaching problems with Sn/SiO2 and Ce/SiO2 materials, the synthesis of trans-carveol was performed under homogeneous conditions using CeCl3 or SnCl2 as catalysts with a catalyst turnover number up to ca. 1200. The method represents one of the few examples of the synthesis of isomers from α-pinene oxide, other than campholenic aldehyde, with a sufficient for practical usage selectivity.
- Costa, Vinícius V.,Da Silva Rocha, Kelly A.,De Sousa, Líniker F.,Robles-Dutenhefner, Patricia A.,Gusevskaya, Elena V.
-
-
Read Online
- Phosphotungstic acid as a versatile catalyst for the synthesis of fragrance compounds by α-pinene oxide isomerization: Solvent-induced chemoselectivity
-
The remarkable effect of the solvent on the catalytic performance of H 3PW12O40, the strongest heteropoly acid in the Keggin series, allows direction of the transformations of α-pinene oxide (1) to either campholenic aldehyde (2), trans-carveol (3), trans-sobrerol (4a), or pinol (5). Each of these expensive fragrance compounds was obtained in good to excellent yields by using an appropriate solvent. Solvent polarity and basicity strongly affect the reaction pathways: nonpolar nonbasic solvents favor the formation of aldehyde 2; polar basic solvents favor the formation of alcohol 3; whereas in polar weakly basic solvents, the major products are compounds 4a and 5. On the other hand, in 1,4-dioxane, which is a nonpolar basic solvent, both aldehyde 2 and alcohol 3 are formed in comparable amounts. The use of very low catalyst loading (0.005-1 mol%) and the possibility of catalyst recovery and recycling without neutralization are significant advantages of this simple, environmentally benign, and low-cost method. This method represents the first example of the synthesis of isomers from α-pinene oxide, other than campholenic aldehyde, with a selectivity that is sufficient for practical usage.
- Da Silva Rocha, Kelly A.,Hoehne, Juliana L.,Gusevskaya, Elena V.
-
-
Read Online
- Pauson-Khand Reactions with Concomitant C?O Bond Cleavage for the Preparation of 5,5- 5,6- and 5,7-Bicyclic Ring Systems
-
Pauson-Khand reactions (PKR) with concomitant C?O bond cleavage have been developed for construction of 5,5- 5,6- and 5,7-bicyclic ring systems bearing complex stereochemistry. The chemistry generates intermolecular PKR-type products in an absolute regio- and stereochemical control which is hardly achievable through real intermolecular Pauson-Khand reactions. A mechanism for this Pauson-Khand reaction has been proposed based on deuterium labelling experiments. (Figure presented.).
- Ma, Ding,Hu, Naifeng,Ao, Junli,Zang, Shaoli,Yu, Guo,Liang, Guangxin
-
supporting information
p. 1887 - 1891
(2021/02/26)
-
- Chiral Imidazo[1,5- a]pyridine-Oxazolines: A Versatile Family of NHC Ligands for the Highly Enantioselective Hydrosilylation of Ketones
-
Herein we report the synthesis and application of a versatile class of N-heterocyclic carbene ligands based on an imidazo[1,5-a]pyridine-3-ylidine backbone that is fused to a chiral oxazoline auxiliary. The key step in the synthesis of these ligands involves the installation of the oxazoline functionality via a microwave-assisted condensation of a cyano-azolium salt with a wide variety of 2-amino alcohols. The resulting chiral bidentate NHC-oxazoline ligands form stable complexes with rhodium(I) that are efficient catalysts for the enantioselective hydrosilylation of structurally diverse ketones. The corresponding secondary alcohols are isolated in good yields (typically >90%) with good to excellent enantioselectivities (80-93% ee). The reported hydrosilylation occurs at ambient temperatures (40 °C), with excellent functional group tolerability. Even ketones bearing heterocyclic substituents (e.g., pyridine or thiophene) or complex organic architectures are hydrosilylated efficiently, which is discussed further in this report.
- Chinna Ayya Swamy,Varenikov, Andrii,Ruiter, Graham De
-
supporting information
p. 247 - 257
(2020/02/04)
-
- Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
-
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.
-
supporting information
p. 21176 - 21182
(2020/09/17)
-
- Chemoselective Luche-Type Reduction of α,β-Unsaturated Ketones by Magnesium Catalysis
-
The chemoselective reduction of α,β-unsaturated ketones by use of an economic and readily available Mg catalyst has been developed. Excellent yields for a wide range of ketones have been achieved under mild reaction conditions, short times, and low catalyst loadings (0.2-0.5 mol %).
- Jang, Yoon Kyung,Magre, Marc,Rueping, Magnus
-
p. 8349 - 8352
(2019/10/16)
-
- Bimetallic Radical Redox-Relay Catalysis for the Isomerization of Epoxides to Allylic Alcohols
-
Organic radicals are generally short-lived intermediates with exceptionally high reactivity. Strategically, achieving synthetically useful transformations mediated by organic radicals requires both efficient initiation and selective termination events. Here, we report a new catalytic strategy, namely, bimetallic radical redox-relay, in the regio- and stereoselective rearrangement of epoxides to allylic alcohols. This approach exploits the rich redox chemistry of Ti and Co complexes and merges reductive epoxide ring opening (initiation) with hydrogen atom transfer (termination). Critically, upon effecting key bond-forming and -breaking events, Ti and Co catalysts undergo proton transfer/electron transfer with one another to achieve turnover, thus constituting a truly synergistic dual catalytic system.
- Ye, Ke-Yin,Mccallum, Terry,Lin, Song
-
supporting information
(2019/06/24)
-
- Stereodivergent Synthesis of Carveol and Dihydrocarveol through Ketoreductases/Ene-Reductases Catalyzed Asymmetric Reduction
-
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
-
p. 5496 - 5504
(2018/11/30)
-
- Photoinduced Carboborative Ring Contraction Enables Regio- and Stereoselective Synthesis of Multiply Substituted Five-Membered Carbocycles and Heterocycles
-
We report herein a photoinduced carboborative ring contraction of monounsaturated six-membered carbocycles and heterocycles. The reaction produces substituted five-membered ring systems stereoselectively and on preparative scales. The products feature multiple stereocenters, including contiguous quaternary carbons. We show that the reaction can serve as a synthetic platform for ring system alteration of natural products. The reaction can also be used in natural product synthesis. A concise total synthesis of artalbic acid has been enabled by a sequence of photoinduced carboborative ring contraction, Rauhut-Currier reaction, and nitrilase-catalyzed hydrolysis. The synthetic utility of the reaction has been further demonstrated by converting the intermediate organoboranes to alcohols, amines, and alkenes.
- Jin, Shengfei,Nguyen, Vu T.,Dang, Hang T.,Nguyen, Dat P.,Arman, Hadi D.,Larionov, Oleg V.
-
supporting information
p. 11365 - 11368
(2017/08/30)
-
- Hydrogenation of Carbonyl Derivatives with a Well-Defined Rhenium Precatalyst
-
The first efficient and general rhenium-catalyzed hydrogenation of carbonyl derivatives was developed. The key to the success of the reaction was the use of a well-defined rhenium complex bearing a tridentate diphosphinoamino ligand as the catalyst (0.5 mol %) at 70 °C in the presence of H2 (30 bar). The mechanism of the reaction was investigated by DFT(PBE0-D3) calculations.
- Wei, Duo,Roisnel, Thierry,Darcel, Christophe,Clot, Eric,Sortais, Jean-Baptiste
-
-
- Synthesis and properties of novel chiral imidazolium-based ionic liquids derived from carvone
-
A large series of novel chiral imidazolium ionic liquids were synthesized using the terpenoid carvone as the chiral substrate. Their specific rotations were characterized and their potential use in chiral recognition was demonstrated by studying interactions with racemic Mosher's acid salt.
- Santamarta, Francisco,Vilas, Miguel,Tojo, Emilia,Fall, Yagamare
-
p. 31177 - 31180
(2016/04/08)
-
- A General CuCl2-Promoted Alkene Aminochlorination Reaction
-
A CuCl2-promoted alkene aminochlorination reaction has been developed. A variety of anilides that contain a mono-, di-, or trisubstituted alkenyl moiety readily participated in this reaction to afford structurally diverse vicinal chloroamines. Studies suggest that the process proceeds by a radical-type mechanism and that CuCl2serves as both the oxidant to generate the amidyl radical as well as the chloride source.
- Li, Shu-Qi,Xiong, Peng,Zhu, Lin,Qian, Xiang-Yang,Xu, Hai-Chao
-
supporting information
p. 3449 - 3455
(2016/07/23)
-
- Photoredox Activation of SF6for Fluorination
-
We report the first practical use of SF6as a fluorinating reagent in organic synthesis. Photoredox catalysis enables the in situ conversion of SF6, an inert gas, into an active fluorinating species by using visible light. Under these conditions, deoxyfluorination of allylic alcohols is effected with high chemoselectivity and is tolerant of a wide range of functional groups. Application of the methodology in a continuous-flow setup achieves comparable yields to those obtained with a batch setup, while providing drastically increased material throughput of valuable allylic fluoride products.
- McTeague, T. Andrew,Jamison, Timothy F.
-
supporting information
p. 15072 - 15075
(2016/11/25)
-
- TERPENE AND TERPENOID DERIVATIVES CONTAINING VINYL GROUPS FOR THE PREPARATION OF POLYMERS
-
The invention relates to a method for producing functionalised monomers, the method comprising: a) providing a starting material selected from terpenes and terpenoids; b) forming a derivative of the starting material by incorporation of a hydroxyl group; c) esterifying the hydroxyl group of the derivative to introduce a moiety containing a vinyl group, so as to produce a functionalised monomer. The functionalised monomer can be polymerised to obtain a bio-derived polymer.
- -
-
Page/Page column 46; 49
(2015/11/10)
-
- Comparative anticonvulsant study of epoxycarvone stereoisomers
-
Stereoisomers of the monoterpene epoxycarvone (EC), namely (+)-cis-EC, (-)-cis-EC, (+)-Trans-EC, and (-)-Trans-EC, were comparatively evaluated for anticonvulsant activity in specific methodologies. In the pentylenetetrazole (PTZ)-induced anticonvulsant test, all of the stereoisomers (at 300 mg/kg) increased the latency to seizure onset, and afforded 100% protection against the death of the animals. In the maximal electroshock-induced seizures (MES) test, prevention of tonic seizures was also verified for all of the isomers tested. However, the isomeric forms (+) and (-)-Trans-EC showed 25% and 12.5% inhibition of convulsions, respectively. In the pilocarpine-induced seizures test, all stereoisomers demonstrated an anticonvulsant profile, yet the stereoisomers (+) and (-)-Trans-EC (at 300 mg/kg) showed a more pronounced effect. A strychnine-induced anticonvulsant test was performed, and none of the stereoisomers significantly increased the latency to onset of convulsions; the stereoisomers probably do not act in this pathway. However, the stereoisomers (+)-cis-EC and (+)-Trans-EC greatly increased the latency to death of the animals, thus presenting some protection. The four EC stereoisomers show promise for anticonvulsant activity, an effect emphasized in the isomers (+)-cis-EC, (+)-Trans-EC, and (-)-Trans-EC for certain parameters of the tested methodologies. These results serve as support for further research and development of antiepileptic drugs from monoterpenes.
- Salgado, Paula Regina Rodrigues,Da Fonsêca, Diogo Vilar,Braga, Renan Marinho,De Melo, Cynthia Germoglio Farias,Andrade, Luciana Nalone,De Almeida, Reinaldo Nóbrega,De Sousa, Dami?o Pergentino
-
p. 19660 - 19673
(2015/12/23)
-
- Eco-friendly stereoselective reduction of α,β-unsaturated carbonyl compounds by Er(OTf)3/NaBH4 in 2-MeTHF
-
An operationally simple and environmentally benign catalytic procedure has been developed to selectively reduce different α,β-unsaturated ketones. The corresponding allylic alcohols are obtained with high chemo- and diastereoselectivity using Er(OTf)3 and NaBH4 in 2-MeTHF. This protocol reduces the amount of catalyst and NaBH4 needed, compared to classical procedures and the stages of extraction/purification are carried out in aqueous solutions avoiding the use of toxic solvents. Taking into account that Er(OTf)3 can be considered even less toxic than table salt and the 'greenness' of 2-MeTHF as a solvent, the system Er(OTf)3/2-MeTHF can be proposed as a cheap, efficient, and environmentally sustainable reduction system for the synthesis of allylic alcohols.
- Nardi, Monica,Sindona, Giovanni,Costanzo, Paola,Oliverio, Manuela,Procopio, Antonio
-
p. 1132 - 1135
(2015/02/19)
-
- Borinic Acid Catalyzed, Regioselective Chloroacylations and Chlorosulfonylations of 2,3-Epoxy Alcohols
-
In the presence of a borinic acid derived catalyst, 2,3-epoxy alcohols undergo couplings with acyl and sulfonyl chlorides. This transformation directly generates O-acylated or O-sulfonylated chlorohydrin diols, with significant levels of regioselectivity for both the ring-opening and O-functionalization steps.
- Tanveer, Kashif,Jarrah, Kareem,Taylor, Mark S.
-
supporting information
p. 3482 - 3485
(2015/07/28)
-
- Engineering Rieske Non-Heme Iron Oxygenases for the Asymmetric Dihydroxylation of Alkenes
-
The asymmetric dihydroxylation of olefins is of special interest due to the facile transformation of the chiral diol products into valuable derivatives. Rieske non-heme iron oxygenases (ROs) represent promising biocatalysts for this reaction as they can be engineered to efficiently catalyze the selective mono- and dihydroxylation of various olefins. The introduction of a single point mutation improved selectivities (≥95 %) and conversions (>99 %) towards selected alkenes. By modifying the size of one active site amino acid side chain, we were able to modulate the regio- and stereoselectivity of these enzymes. For distinct substrates, mutants displayed altered regioselectivities or even favored opposite enantiomers compared to the wild-type ROs, offering a sustainable approach for the oxyfunctionalization of a wide variety of structurally different olefins. Modulation by mutation: Rieske non-heme iron oxygenases can be used as efficient biocatalysts for the selective oxyfunctionalization of various olefins yielding vicinal cis-diols and allylic alcohols. Introduction of a single amino acid substitution in the active sites of two selected oxygenases resulted in variants with improved stereoselectivities and product formations.
- Gally, Christine,Nestl, Bettina M.,Hauer, Bernhard
-
supporting information
p. 12952 - 12956
(2015/11/02)
-
- Catalytic isomerisation of α-pinene oxide in the presence of ETS-10 supported ferrocenium ions
-
Ferrocenium ions, [Fc]+, have been immobilised in the microporous titanosilicate ETS-10 by ion exchange of Na+/K+ ions under hydrothermal conditions. The resultant hybrid inorganic-organometallic (ETS-10/[Fc]+) material was characterised by elemental analysis, diffuse reflectance UV-Vis spectroscopy, FT-IR spectroscopy, powder X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The ETS-10/[Fc]+ sample was tested as a catalyst for the isomerisation of α-pinene oxide (PinOx) at 35 C. With α, α, α-trifluorotoluene (TFT) as solvent, campholenic aldehyde (CPA) was the main product formed in 38% yield at 100% conversion and 30 min reaction. Other reaction products included trans-carveol, iso-pinocamphone and trans-pinocarveol. The same PinOx conversion and CPA yield could be reached within 1 min reaction time by increasing the reaction temperature (to 55 °C) and the Fe:PinOx molar ratio. Other solvents (hexane, CH3CN, toluene) led to poorer results than TFT. Characterisation of the used catalyst, together with an analysis of the catalytic activity of the liquid phase obtained after contact of ETS-10/[Fc]+ with TFT, indicated that the ETS-10/[Fc]+ sample was resistant toward leaching of iron-containing active species. When the recovered solid was reused in a second batch run, catalytic activity was lower than in the first run, while selectivity to CPA was higher.
- Bruno, Sofia M.,Gomes, Ana C.,Coelho, Ana C.,Brand?o, Paula,Valente, Anabela A.,Pillinger, Martyn,Gon?alves, Isabel S.
-
-
- Monoterpene hydroxylation with an artificial self-sufficient P450 utilizing a P450SMO reductase domain for the electron transfer
-
Cytochrome P450SMO from Rhodococcus sp. ECU0066 is a natural self-sufficient P450 monooxygenase, consisting of a heme domain, a flavin-reductase domain containing FMN and NADPH binding sites, and a [Fe2S2] ferredoxin domain. P450cam catalyzes the hydroxylation of camphor to 5-exo-hydroxycamphor. The variant P450cam (Y96F/V247L) was reported for the oxidation of monoterpene by protein engineering. In this work, we constructed an artificial self-sufficient P450-type monoterpene hydroxylase by connecting the P450SMO reductase domain and the P450cam (Y96F/V247L) domain together with a linker region (G4S)4. The resultant chimeric P450 enzyme could catalyze the hydroxylation of (-)-limonene and α-pinene as well as camphor, which were all inactive for the natural fusion protein P450SMO. Co-expression of the fused P450 with a glucose dehydrogenase (GDH) improved the (-)-limonene conversion as sufficient NADPH was regenerated in the system with glucose as a cosubstrate. This work illustrated that P450SMO reductase might act as an electron donor partner of P450s and might be used for fusion with heterogeneous P450 domains to elucidate the catalytic function of other unknown P450s.
- Luan, Zheng-Jiao,Yin, Yue-Cai,Li, Ai-Tao,Yu, Hui-Lei,Xu, Jian-He
-
-
- Application of an indenyl molybdenum dicarbonyl complex in the isomerisation of α-pinene oxide to campholenic aldehyde
-
The complex [{(η5-Ind)Mo(CO)2(μ-Cl)} 2] (1) has been tested for the industrially relevant catalytic isomerisation of α-pinene oxide (PinOx) to campholenic aldehyde (CPA) in the liquid phase. PinOx conversion and CPA selectivity are strongly influenced by the solvent employed. Complete conversion of PinOx was achieved within 1 min at 55 °C or 30 min at 35 °C using 1,2-dichloroethane as solvent, giving CPA in 68% yield. Other products included trans-carveol, iso-pinocamphone and trans-pinocarveol. The stability of 1 under the reaction conditions used was investigated by using FT-IR spectroscopy and electrospray ionisation mass spectrometry (ESI-MS) to characterise recovered solids. In the presence of air/moisture 1 undergoes oxidative decarbonylation upon dissolution to give oxomolybdenum species that are proposed to include a tetranuclear oxomolybdenum(v) complex. Conversely, ESI-MS studies of 1 dissolved in dry acetonitrile show mononuclear species of the type [IndMo(CO)2(CH 3CN)n]+. The crystal structure of the ring-slipped dicarbonyl complex [(η3-Ind)Mo(CO) 2Cl(CH3CN)2] (2) (obtained after dissolution of 1 in acetonitrile) is reported. the Partner Organisations 2014.
- Bruno, Sofia M.,Gomes, Ana C.,Gamelas, Carla A.,Abrantes, Marta,Oliveira, M. Concei??o,Valente, Anabela A.,Almeida Paz, Filipe A.,Pillinger, Martyn,Rom?o, Carlos C.,Gon?alves, Isabel S.
-
p. 3172 - 3180
(2014/07/07)
-
- Isomerization of bicyclic terpene epoxides into allylic alcohols without changing of the initial structure
-
A novel method of (1S,2R,3R,5R)-6,6-dimethyl-4-methylenebicyclo[3.1.1] heptane-2,3-diol synthesis, which is a valuable intermediate in the synthesis of a perspective potent anti-Parkinson drugs, in the presence of TiO2 was proposed. Catalytic activity of TiO2 in the bicyclic terpene epoxides isomerization to corresponding allylic alcohols without changing of the initial structure was demonstrated, contrary to titania-supported Au catalysts which promoted rearrangement with predominant formation of a cyclopentene α-hydroxy ketone.
- Demidova, Yu.S.,Ardashov,Simakova,Simakova,Volcho,Salakhutdinov,Murzin, D.Yu.
-
p. 162 - 166
(2014/06/09)
-
- Catalytic olefin epoxidation with a carboxylic acid-functionalized cyclopentadienyl molybdenum tricarbonyl complex Dedicated to Prof. Maria José Calhorda on the occasion of her 65th birthday and in recognition of her outstanding contributions to the field of computational organometallic chemistry.
-
The complex CpMo(CO)3CH2COOH (1) (Cp = η5-C5H5) has been examined as a precatalyst for the epoxidation of cis-cyclooctene and α-pinene using tert-butylhydroperoxide (TBHP) as oxidant. A high turnover frequency of ca. 600 mol molMo-1 h-1 was achieved in the epoxidation of cyclooctene, giving the epoxide as the only reaction product. With α-pinene as substrate, the added-value products α-pinene oxide and campholenic aldehyde were obtained. Two different approaches to facilitate catalyst recovery and reuse were explored: (1) use of an ionic liquid (IL) as solvent, and (2) intercalation of 1 in a Zn,Al layered double hydroxide (LDH) by a direct synthesis (coprecipitation) route. Characterization of the LDH by powder X-ray diffraction, thermogravimetric analysis, FT-IR and 13C CP MAS NMR spectroscopies showed that the CpMo(CO)3CH 2COO- anions intercalate in a bilayer arrangement, resulting in an interlayer spacing of 20.7 A?. In the epoxidation of cyclooctene, catalytic activity in the first batch run was very high for the catalyst/IL mixture and moderate for the LDH. Characterization of the LDH after catalysis indicated that nearly complete oxidative decarbonylation of supported complexes had occurred (by reaction with TBHP), resulting in the presence of immobilized oxomolybdenum species. However, catalytic activities for both the recovered LDH and catalyst/IL decreased in consecutive runs, due in part to progressive removal of active species during either the catalytic reaction (for the LDH) or the solvent extraction/work-up (for the catalyst/IL mixture).
- Gomes, Ana C.,Bruno, Sofia M.,Abrantes, Marta,Magalh?es, Clara I.R.,Gon?alves, Isabel S.,Valente, Anabela A.,Pillinger, Martyn
-
p. 205 - 211
(2014/05/06)
-
- Substrate flexibility and reaction specificity of tropinone reductase-like short-chain dehydrogenases
-
Annotations of protein or gene sequences from large scale sequencing projects are based on protein size, characteristic binding motifs, and conserved catalytic amino acids, but biochemical functions are often uncertain. In the large family of short-chain dehydrogenases/reductases (SDRs), functional predictions often fail. Putative tropinone reductases, named tropinone reductase-like (TRL), are SDRs annotated in many genomes of organisms that do not contain tropane alkaloids. SDRs in vitro often accept several substrates complicating functional assignments. Cochlearia officinalis, a Brassicaceae, contains tropane alkaloids, in contrast to the closely related Arabidopsis thaliana. TRLs from Arabidopsis and the tropinone reductase isolated from Cochlearia (CoTR) were investigated for their catalytic capacity. In contrast to CoTR, none of the Arabidopsis TRLs reduced tropinone in vitro. NAD(H) and NADP(H) preferences were relaxed in two TRLs, and protein homology models revealed flexibility of amino acid residues in the active site allowing binding of both cofactors. TRLs reduced various carbonyl compounds, among them terpene ketones. The reduction was stereospecific for most of TRLs investigated, and the corresponding terpene alcohol oxidation was stereoselective. Carbonyl compounds that were identified to serve as substrates were applied for modeling pharmacophores of each TRL. A database of commercially available compounds was screened using the pharmacophores. Compounds identified as potential substrates were confirmed by turnover in vitro. Thus pharmacophores may contribute to better predictability of biochemical functions of SDR enzymes.
- Reinhardt, Nicole,Fischer, Juliane,Coppi, Ralph,Blum, Elke,Brandt, Wolfgang,Draeger, Birgit
-
-
- Titanocene-promoted stereoselective eliminations on epoxy alcohols derived from R-(-)-carvone
-
The reaction of several stereoisomeric epoxy alcohols, obtained from R-(-)-carvone, and their corresponding formates, acetates, and benzoates, promoted by Cp2TiCl has been studied. The different outcomes of the reaction of epoxy derivatives are rationalized in terms of mechanistically biased processes. The radicals emerging from oxirane cleavage provide two types of reaction: dehydroxylation (deoxycarbonylation) and dehydrogenation. The results offer considerable support for the radical elimination theory of hydroxyl, formyloxyl, and acetoxyl groups. The inability of tertiary radicals to be reduced by the Ti(III) complex is demonstrated unequivocally.
- Fernández-Mateos,Herrero Teijón,Rubio González
-
p. 1611 - 1616
(2013/02/25)
-
- 3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol: The importance of functional groups for antiparkinsonian activity
-
Compounds with different sets of three of the four functional groups of (1R,2R,6S)-3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol 1 possessing high antiparkinsonian activity were synthesized. The synthesized compounds were tested for the antiparkinsonian activity in vivo on a mouse model with MPTP neurotoxin. A pronounced antiparkinsonian effect of 1 can only be achieved if it contains all the four functional groups (two hydroxy groups and two double bonds). The 2-hydroxy group or the 3,4-double bond is not required for stimulating the exploratory activity of the animals.
- Ardashov, Oleg V.,Pavlova, Alla V.,Korchagina, Dina V.,Volcho, Konstantin P.,Tolstikova, Tat'yana G.,Salakhutdinov, Nariman F.
-
p. 731 - 739
(2013/09/23)
-
- Total synthesis of cyrneine A
-
Neuritogenic natural products: The tricyclic diterpene cyrneineA featuring a hexatrienal unit was prepared synthetically for the first time by a Heck reaction, a carbene ring expansion, and a reductive carbonylation. The structure of the natural product was assigned by X-ray crystal analysis of a synthetic sample. Copyright
- Elamparuthi, Elangovan,Fellay, Cindy,Neuburger, Markus,Gademann, Karl
-
supporting information; experimental part
p. 4071 - 4073
(2012/06/01)
-
- Air-stable, nitrile-ligated (cyclopentadienone)iron dicarbonyl compounds as transfer reduction and oxidation catalysts
-
A series of air-stable, nitrile-ligated (cyclopentadienone)iron dicarbonyl compounds was synthesized and their activities as catalysts in the transfer reduction of acetophenone were explored. While all were active catalysts, the acetonitrile adduct was chosen for further study and was found to be active in the transfer reduction of aldehydes and ketones and in the Oppenauer-type oxidation of secondary alcohols. The acetonitrile catalyst exhibited activities similar to those of an analogous air-sensitive iron hydride, but unlike the iron hydride it was unreactive in carbonyl reductions using hydrogen gas. Copyright
- Plank, Taylor N.,Drake, Jessica L.,Kim, Daniel K.,Funk, Timothy W.
-
supporting information; experimental part
p. 597 - 601
(2012/05/04)
-
- Influence of the Br?nsted and Lewis acid sites on the catalytic activity and selectivity of Fe/MCM-41 system
-
The system Fe2O3/MCM-41, with high iron dispersion, was synthesized in order to introduce Lewis acid sites into the MCM-41 structure. Two calcination atmospheres (inert and oxidant) were used to produce iron nanoclusters with different structural properties. Besides, a silylation treatment was realized on both solids with the aim of neutralizing the Br?nsted acidity associated with the MCM-41 silanol groups. The samples were characterized by atomic absorption spectroscopy, X-ray diffraction at low angles, N2 adsorption, temperature-programmed reduction, Fourier transform infrared spectroscopy, nuclear magnetic resonance of 29Si, and M?ssbauer spectroscopy. The influence of the structural changes of the nanoclusters and the effect of the simultaneous presence of Lewis and Br?nsted acid sites were evaluated studying the product distribution from the α-pinene oxide isomerization reaction. It was determined that the Br?nsted acidity of the Fe/MCM-41 system has not the sufficient acid strength to modify the product distribution which is mainly governed by the Lewis sites.
- Fellenz,Bengoa,Marchetti,Gervasini
-
scheme or table
p. 187 - 196
(2012/10/08)
-
- Amberlyst-15: A reusable heterogeneous catalyst for the dehydration of tertiary alcohols
-
Tertiary alcohols react under mild conditions in the presence of Amberlyst-15 (dry) (solid-supported sulfonic acid) to give predominantly the most stable alkene in very good yield. The dehydration of tertiary alcohol functionality occurs without observation of rearrangement and polymerization products, and with outstanding substrate tolerance, which include the NHCBz, NHBoc, OSEM, OTBDMS, OBOM and ethylene ketal functional groups. Amberlyst-15 (dry) can be easily recovered from the reaction medium and reused for five cycles, maintaining the catalytic efficiency. In addition, the dehydration can occur under continuous operation.
- Frija, Luís M.T.,Afonso, Carlos A.M.
-
experimental part
p. 7414 - 7421
(2012/09/22)
-
- Enantioselective synthesis of a key A-ring intermediate for the preparation of 1α,25-dihydroxyvitamin D3
-
A novel approach to the key A-ring α, β-unsaturated aldehyde 1, an important intermediate for the preparation of 1α,25-dihydroxyvitamin D3, has been developed. The strategy started from the inexpensive starting material (R)-carvone with an ene reaction serving as the key step toward the potential synthesis of vitamin D3 analogues bearing the modification at the C-2 position.
- Chen, Yan,Ju, Tong
-
supporting information; experimental part
p. 86 - 89
(2011/04/12)
-
- Dauben-Michno oxidative transposition of allylic cyanohydrins - Enantiomeric switch of (-)-carvone to (+)-carvone
-
Allylic cyanohydrins were subjected to Dauben-Michno oxidation at low temperatures to provide β-cyanoenones in good to excellent yields. The potential of this oxidative transposition as a means of an enantiomeric switch of enones containing a latent plane of symmetry was tested by conversion of (-)-carvone to its enantiomer.
- Hudlicky, Jason R.,Werner, Lukas,Semak, Vladislav,Simionescu, Razvan,Hudlicky, Tomas
-
scheme or table
p. 535 - 543
(2011/10/03)
-
- Radical reactions on pinene-oxide derivatives induced by Ti(III)
-
A practical, brief and selective synthesis of several pinene oxide derived terpenoids can be achieved from readily available starting materials. The key step is a radical reaction promoted by titanocene chloride.
- Fernández-Mateos,Herrero Teijón,Rubio González
-
supporting information; experimental part
p. 9529 - 9534
(2011/12/15)
-
- Chiral building blocks from R-(-)-carvone: N-bromosuccinimidemediated addition-sceletal rearrangement of (-)-cis-carveol
-
Synthetically valuable bicyclic blocks 5, 7 and 9 were prepared by the oxidative cleavage of the double bond of 4 with the RuCl3-NaIO4 system and O3.
- Valeev, Ruslan F.,Selezneva, Nataliya K.,Starikova, Zoya A.,Pankrat'ev, Evgenii Yu.,Miftakhov, Mansur S.
-
scheme or table
p. 77 - 79
(2010/06/19)
-
- New orthogonally functionalized synthetic blocks from R-(-)-carvone
-
The intramolecular cyclization of (-)-cis-carveol under iodine treatment afforded (1R,5R,6S)-6-iodomethyl-2,6-dimethyl-7-oxabicyclo[3.2.1]oct-2-ene that was subjected to allyl oxydation with the complex CrO3DMP giving a synthetically valuable building block, (1R,5R,6S)-6-iodomethyl-2,6-dimethyl-7- oxabicyclo[3.2.1]oct-2-ene-4-one. In the latter the double bond was cleaved by ozonization to obtain the expected trioxo derivative, and the subsequent ozonolysis of its enol form provided a multiple functionalized tetrahydrofuran derivative. Pleiades Publishing, Ltd., 2010.
- Valeev,Khasanova,Miftakhov
-
experimental part
p. 670 - 673
(2010/10/04)
-
- Studies towards the taming of the 'carbocation' in the regioselective ring opening of epoxides to allylic alcohols
-
Regioselective isomerisation of epoxides to allylic alcohols can be achieved using p-toluenesulfonic acid in the presence of 1,3- dimethylimidazolidin-2-one. Georg Thieme Verlag Stuttgart.
- Chapman, Helen A.,Herbal, Karim,Motherwell, William B.
-
experimental part
p. 595 - 598
(2010/09/15)
-
- Synthesis and some transformations of (-)-carveol
-
Reduction of the oxo group in (-)-carvone with LiAlH4, NaBH4, and (i-Bu)2AlH was performed. It was found that the reduction with the system CeCl3 ? 7 H2O-NaBH4 in methanol at 20°C is the most practical procedure for the synthesis of (-)-carveol. Solvolysis of (-)-carvyl methanesulfonate gave products of SN2 and SN2' replacement of the methylsulfonyloxy group, the latter slightly prevailing. Overman rearrangement of (-)-carveol resulted in the formation of the corresponding trichloroacetamide derivative, and intramolecular iodoetherification of the title compound afforded 6-iodomethyl-2,6-dimethyl-7-oxabicyclo[3.2.1]oct-2-ene. Pleiades Publishing, Ltd., 2009.
- Valeev,Vostrikov,Miftakhov
-
experimental part
p. 810 - 814
(2009/12/09)
-
- Titanocene-promoted intermolecular couplings of epoxides with nitriles. An easy access to β-hydroxyketones
-
(Chemical Equation Presented) Radical couplings of epoxides and nitriles mediated by Cp2TiCl provide a diastereoselective route to the synthesis of β-hydroxyketones. The conditions of this "aldol- like" reaction are mild enough to avoid the dehydration of the β-hydroxyketone. The scope of the coupling reaction with functionalized and tetrasubstituted epoxides has been studied. The radical character of the coupling reactions is demonstrated.
- Fernandez-Mateos,Encinas Madrazo,Herrero Teijon,Rubio Gonzalez
-
supporting information; experimental part
p. 3913 - 3918
(2009/10/20)
-
- Metal-catalyzed silylene insertions of allylic ethers: Stereoselective formation of chiral allylic silanes
-
Silylene insertion into allylic ethers occurs suprafacially to provide enantioenriched allylic silanes and disilanes. Silylene insertion to a variety of protected allylic alcohols utilizing silver- and copper-mediated conditions proved to be a general method for allylic silane formation. Allylic disilanes reacted similarly to allylic silanes, undergoing both annulation and allylation reactions. Copyright
- Bourque, Laura E.,Cleary, Pamela A.,Woerpel
-
p. 12602 - 12603
(2008/09/16)
-
- Pyridinium chlorochromate mediated oxidative cyclisation of sterically crowded γ,δ-unsaturated alcohols
-
Pyridinium chlorochromate (PCC) mediated oxidative cyclisation of sterically crowded γ,δ-unsaturated alcohols (primary, secondary, allylic, benzylic as well as tertiary) is described.
- Srikrishna,Vasantha Lakshmi,Sudhakar
-
p. 7610 - 7613
(2008/03/14)
-
- Synthesis of enantiomerically pure β-azidoselenides starting from natural terpenes
-
Several unsaturated natural terpenes have been easily converted, in good yields, into the corresponding enantiomerically pure β-azidoselenides by addition of the electrophilic selenium reagent PhSeOTf in the presence of sodium azide. These reactions are stereospecific anti additions, which occur with a Markovnikov orientation. Examples of the synthetic importance of these β-azidoselenides are also reported.
- Tiecco, Marcello,Testaferri, Lorenzo,Santi, Claudio,Tomassini, Cristina,Santoro, Stefano,Marini, Francesca,Bagnoli, Luana,Temperini, Andrea
-
p. 12373 - 12378
(2008/03/14)
-
- Cyclic allyl carbamates in stereoselective syn SE′ processes: Synthetic approach to sarcodictyins and eleutherobin
-
Our synthetic approach of marine diterpenoids sarcodictyins A and B and eleutherobin relies on the one-step attachment of a C5-C9 side chain at the C10 position. The C1, C10 cis-disubstituted cyclohexene derivative is obtained in 86 % yield with total stereoselectivity. The reaction is based on a syn S E′ process involving a cyclic (Z)-allyl diisopropylcarbamate. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Dhulut, Sylvie,Bourin, Arnaud,Lannou, Marie-Isabelle,Fleury, Etienne,Lensen, Nathalie,Chelain, Evelyne,Pancrazi, Ange,Ardisson, Janick,Fahy, Jacques
-
p. 5235 - 5243
(2008/03/18)
-
- Hydrazine hydrate induced reductive cleavage of α,β-epoxy ketones: An efficient procedure for the preparation of β-hydroxy ketones
-
An efficient and general procedure for the reductive cleavage of α,β-epoxy ketones to the corresponding β-hydroxy ketones, using hydrazine hydrate in ethanol at low temperatures, is described.
- Salvador, Jorge A.R.,Leit?o, Alcino J.L.,Sá E Melo, M. Luísa,Hanson, James R.
-
p. 1067 - 1070
(2007/10/03)
-
- A radical cyclisation based cyclopentenone annulation of allyl alcohols
-
A four-step cyclopentenone annulation reaction of allylic alcohols employing a 5-exo-trig radical cyclisation reaction of mixed allyl methyl ketals of bromoacetone as the key step is described. The annulated product 12b obtained from 2,3-dimethylcyclohexenol has been further elaborated into (±)-epibakkenolides employing a 5-exo-dig radical cylisation reaction based α-spiro-β-methylene-γ-butyrolactone annulation methodology.
- Srikrishna,Viswajanani,Sattigeri
-
p. 2975 - 2983
(2007/10/03)
-
- Stereoselective synthesis of enantiomerically pure, orthogonally protected 2-methylenecyclohexane-1,3,5-triols and 2,4,6-trihydroxycyclohexanones
-
The triply silyl protected 2-methylenecyclohexane-1,3,5-triols 1a-c (C-1: tert-butyldimethylsilyl, TBDMS; C-3: trimethylsilyl, TMS; C-5: tert-butyldiphenylsilyl, TBDPS) were prepared from (R)-(-)-carvone in seven synthetic steps (overall yields: 29-53%). Ozonolysis in the presence of triethylamine yielded the triply protected 2,4,6-trihydroxycyclohexanones 2a-c (85%-quant.). The configuration of the products was proven by NOESY studies and by chemical correlation.
- Kirsch, Stefan,Bach, Thorsten
-
p. 1827 - 1836
(2007/10/03)
-
- First comprehensive bakkane approach: Stereoselective and efficient dichloroketene-based total syntheses of (±)- and (-)-9-acetoxyfukinanolide, (±)- and (+)-bakkenolide a, (-)-bakkenolides III, B, C, H, L, V, and X, (±)- and (-)-homogynolide A, (±)-homogynolide B, and (±)-palmosalide C
-
Cycloaddition of dichloroketene with dimethylcyclohexenes has been used as the key reaction in an efficient, general approach to the bakkanes. New methods and methodologies that have been developed in this work include spiro β-methylene-γ-butyrolactonizations, a vicinal dicarboxylation, an angelic ester preparation, a transesterification, an epoxy ketone double reduction, and a retro aldol-aldol approach to low-energy aldol isomers.
- Brocksom, Timothy J.,Coelho, Fernando,Depres, Jean-Pierre,Greene, Andrew E.,Freire de Lima, Marco E.,Hamelin, Olivier,Hartmann, Benoit,Kanazawa, Alice M.,Wang, Yanyun
-
p. 15313 - 15325
(2007/10/03)
-
- Sex differences in the metabolism of (+)- and (-)-limonene enantiomers to carveol and perillyl alcohol derivatives by cytochrome P450 enzymes in rat liver microsomes
-
(+)-Limonene is reported to cause nephropathy in male rats, but not in female rats and other species of animals including mice, rabbits, guinea pigs, and dogs. Male rats contain high levels of α2u-globulin in kidneys, and it has been shown that limonene a
- Miyazawa, Mitsuo,Shindo, Masaki,Shimada, Tsutomu
-
-