- First enantioselective synthesis of marine diterpene ambliol-A
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The first enantioselective synthesis of furanditerpene ambliol-A, which is a major metabolite of marine sponge Dysidea amblia, has been accomplished by starting from racemic α-ionone. The key steps of the synthesis include lipase-mediated resolution of 4-hydroxy-γ-ionone, its stereoselective transformation into trans-α-epoxy-dihydroionone, C2 homologation to trans-α-epoxy-monocyclofarnesyl acetate and Li2CuCl4-catalysed sp3-sp3 cross-coupling reaction of the latter ester with (furan-3-ylmethyl)magnesium chloride. This work confirms the chemical structure previously assigned to ambliol-A and proves that the natural levorotatory isomer does not possess (1S,2S) absolute configuration, as previously indicated, but is the opposite enantiomer, (1R,2R)-2-[(E)-6-(furan-3-yl)-3-methylhex-3-enyl]-1,3,3-trimethylcyclohexanol.
- Serra, Stefano,Lissoni, Veronica
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- I2-PPh3 mediated spiroannulation of unsaturated β-dicarbonyl compounds. the first synthesis of (±)-negundoin A
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An efficient and stereoselective spiroannulation of unsaturated enols is reported. Unsaturated β-dicarbonyl compounds undergo cyclization by reaction with catalytic I2-PPh3, affording the corresponding spiro enol ether derivatives, with complete regio- and stereoselectivity, under mild conditions. Utilizing this new methodology, the first total synthesis of the anti-inflammatory diterpene negundoin A and a naturally occurring trypanocidal aldehyde is reported.
- Tapia, Ruben,Cano, M. Jose,Bouanou, Hanane,Alvarez, Esteban,Alvarez-Manzaneda, Ramon,Chahboun, Rachid,Alvarez-Manzaneda, Enrique
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Read Online
- Asymmetric Cation-Olefin Monocyclization by Engineered Squalene–Hopene Cyclases
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Squalene–hopene cyclases (SHCs) have great potential for the industrial synthesis of enantiopure cyclic terpenoids. A limitation of SHC catalysis has been the enzymes’ strict (S)-enantioselectivity at the stereocenter formed after the first cyclization step. To gain enantio-complementary access to valuable monocyclic terpenoids, an SHC-wild-type library including 18 novel homologs was set up. A previously not described SHC (AciSHC) was found to synthesize small amounts of monocyclic (R)-γ-dihydroionone from (E/Z)-geranylacetone. Using enzyme and process optimization, the conversion to the desired product was increased to 79 %. Notably, analyzed AciSHC variants could finely differentiate between the geometric geranylacetone isomers: While the (Z)-isomer yielded the desired monocyclic (R)-γ-dihydroionone (>99 % ee), the (E)-isomer was converted to the (S,S)-bicyclic ether (>95 % ee). Applying the knowledge gained from the observed stereodivergent and enantioselective transformations to an additional SHC-substrate pair, access to the complementary (S)-γ-dihydroionone (>99.9 % ee) could be obtained.
- Aeberli, Natalie,Berweger, Raphael,Bornscheuer, Uwe T.,Buller, Rebecca,Dossenbach, Sandro,Eichenberger, Michael,Eichhorn, Eric,Flachsmann, Felix,Hüppi, Sean,Hortencio, Lucas,Patsch, David,Voirol, Francis,Vollenweider, Sabine
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supporting information
p. 26080 - 26086
(2021/09/20)
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- Highly Selective Hydrogenation of C═C Bonds Catalyzed by a Rhodium Hydride
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Under mild conditions (room temperature, 80 psi of H2) Cp*Rh(2-(2-pyridyl)phenyl)H catalyzes the selective hydrogenation of the C═C bond in α,β-unsaturated carbonyl compounds, including natural product precursors with bulky substituents in the β position and substrates possessing an array of additional functional groups. It also catalyzes the hydrogenation of many isolated double bonds. Mechanistic studies reveal that no radical intermediates are involved, and the catalyst appears to be homogeneous, thereby affording important complementarity to existing protocols for similar hydrogenation processes.
- Gu, Yiting,Lisnyak, Vladislav G.,Norton, Jack R.,Salahi, Farbod,Snyder, Scott A.,Zhou, Zhiyao
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supporting information
p. 9657 - 9663
(2021/07/19)
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- Hydroformylation of recalcitrating biorenewable compounds containing trisubstituted double bonds
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Hydroformylation is a useful tool in industrial organic syntheses and it is easily applied to substrates containing terminal C[sbnd]C double bonds. Applying this reaction to substrates containing other functionalities or trisubstituted C[sbnd]C double bonds is not straightforward. Herein, the hydroformylation of several biorenewable alkenes with these features, namely: α-terpineol, terpinen-4-ol, limonene (double hydroformylation), and α-ionone, is presented. Only by the judicious choice of the catalytic system and reaction conditions, was it possible to obtain good yields and selectivity for these substrates.
- Faria, Amanda de Camargo,de Oliveira, Mileny P.,Monteiro, Amanda C.,Mota, Rayssa L.V.,Oliveira, Kelley C.B.,Santos, Eduardo N. dos,Gusevskaya, Elena V.
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- Capturing the Monomeric (L)CuH in NHC-Capped Cyclodextrin: Cavity-Controlled Chemoselective Hydrosilylation of α,β-Unsaturated Ketones
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The encapsulation of copper inside a cyclodextrin capped with an N-heterocyclic carbene (ICyD) allowed both to catch the elusive monomeric (L)CuH and a cavity-controlled chemoselective copper-catalyzed hydrosilylation of α,β-unsaturated ketones. Remarkably, (α-ICyD)CuCl promoted the 1,2-addition exclusively, while (β-ICyD)CuCl produced the fully reduced product. The chemoselectivity is controlled by the size of the cavity and weak interactions between the substrate and internal C?H bonds of the cyclodextrin.
- Bistri-Aslanoff, Olivia,Derat, Etienne,Leloux, Sébastien,Leyssens, Tom,Ménand, Micka?l,Meijide Suárez, Jorge,Riant, Olivier,Roland, Sylvain,Sollogoub, Matthieu,Xu, Guangcan,Zhang, Pinglu,Zhang, Yongmin
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supporting information
p. 7591 - 7597
(2020/03/23)
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- Synthesis of the BCDE molecular fragment of azadiradione mediated by titanocene(III)
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A practical, short, and diastereoselective synthesis of the azadiradione BCDE fragment from a readily available starting material is described. The key step was the titanocene(III)-promoted tandem cyclization of unsaturated epoxy nitrile.
- Fernandez-Mateos,Madrazo, S. Encinas,Teijon, P. Herrero,Clemente, R. Rabanedo,Gonzalez, R. Rubio,Gonzalez, F. Sanz
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p. 9571 - 9578
(2013/10/22)
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- (BDP)CuH: A "hot" Stryker's reagent for use in achiral conjugate reductions
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(Chemical Equation Presented) A ligand-modified, economical version of Stryker's reagent (SR) has been developed based on a bidentate, achiral bis-phosphine. Generated in situ, "(BDP)CuH" smoothly effects conjugate reductions of a variety of unsaturated substrates, including those that are normally unreactive toward SR. Substrate-to-ligand ratios typically on the order of 1000-10000:1 can be used leading to products in high yields.
- Baker, Benjamin A.,Boskovic, Zarko V.,Lipshutz, Bruce H.
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p. 289 - 292
(2008/09/19)
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- Lewis base-catalyzed conjugate reduction and reductive aldol reaction of α,β-unsaturated ketones using trichlorosilane
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Lewis bases such as Ph3P=O and HMPA catalyze the 1,4-reduction of α,β-unsaturated ketones with trichlorosilane, and because the 1,2-reduction of aldehydes scarcely proceeded under the conditions, one-pot reductive aldol reactions with aldehydes were successfully achieved; preliminary studies using a chiral Lewis base revealed a high potential for enantioselective catalysis. The Royal Society of Chemistry.
- Sugiura, Masaharu,Sato, Norimasa,Kotani, Shunsuke,Nakajima, Makoto
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supporting information; experimental part
p. 4309 - 4311
(2009/03/12)
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- Conjugate reduction of α,β-unsaturated carbonyl compounds promoted by nickel nanoparticles
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The system composed of nickel(II) chloride, lithium metal, a catalytic polymer-supported arene, and ethanol, has been efficiently applied to the conjugate reduction of a variety of α,β-unsaturated carbonyl compounds (ketones and carboxylic acid derivatives) under very mild reaction conditions. Georg Thieme Verlag Stuttgart.
- Alonso, Francisco,Osante, I?aki,Yus, Miguel
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p. 3017 - 3020
(2008/02/12)
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- Biomimetic cyclization of small terpenoids promoted by zeolite NaY: Tandem formation of α-ambrinol from geranyl acetone
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Zeolite NaY promotes efficiently the biomimetic cyclization of small acyclic terpenes. Geranyl and neryl acetone undergo a novel tandem 1,5-diene cyclization/carbonyl-ene reaction to form the natural product α-ambrinol isolated in >65% yield.
- Tsangarakis, Constantinos,Stratakis, Manolis
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p. 1280 - 1284
(2007/10/03)
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- Development of a continuous-flow system for catalysis with palladium(0) particles
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Heterogeneous catalysis for organic synthesis under continuous-flow conditions becomes possible by a new reactor-based approach. Continuous-flow reactors with a monolithic glass/polymer composite interior are loaded with palladium particles by ion exchange followed by reduction. When incorporated into a continuous-flow setup (PASSflow) this reactor allows the transfer-hydrogenation of alkenes, alkynes, nitro-substituted aromatic compounds and benzyl ethers in the flow-through mode. In addition, the activity of the catalysts is well suited to achieve Suzuki, Sonogashira and Heck cross-coupling reactions in the absence of phosphanes or any other ligands, resulting in a greatly simplified purification. As an extension to this concept a bifunctional support was prepared inside the reactor consisting of Pd particles and an ion-exchange group (hydroxide form). In the Suzuki-Miyaura reaction the reactor serves as a base for immobilisation and activation of the boronic acid as boronate and as a catalyst for promoting the C-C coupling reaction under continuous-flow conditions. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Solodenko, Wladimir,Wen, Hongliang,Leue, Stefanie,Stuhlmann, Friedrich,Sourkouni-Argirusi, Georgia,Jas, Gerhard,Schoenfeld, Hagen,Kunz, Ulrich,Kirschning, Andreas
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p. 3601 - 3610
(2007/10/03)
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- Chlorosulfonic acid as a convenient electrophilic olefin cyclization agent
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Among several sulfonic acids studied (MeSO3H, p-TsOH, H2SO4, ClSO3H, FSO3H), the scarcely used chlorosulfonic acid showed to be an efficient agent for electrophilic olefin cyclizations with internal nucleophilic termination, in a similar manner that is well-established with fluorosulfonic acid. Its availability, lower price and relatively lesser handling problems makes ClSO3H an advantageous cyclizing agent particularly for high-scale applications. The stereochemical outcome of these cyclizations has been rationalized.
- Linares-Palomino, Pablo J.,Salido, Sofía,Altarejos, Joaquín,Sánchez, Adolfo
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p. 6651 - 6655
(2007/10/03)
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- Compounds having protected hydroxy groups
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The present invention relates to compounds with protected hydroxy groups of formula (I) These compounds are precursors for organoleptic agents, such as fragrances, and masking agents and for antimicrobial agents. When activated, the compounds of formula (I) are cleaved and form one or more organoleptic and/or antimicrobial compounds.
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- Compounds having protected hydroxy groups
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The present invention relates to compounds with protected hydroxy groups of formula (I) These compounds are precursors for organoleptic agents, such as fragrances, and masking agents and for antimicrobial agents. When activated, the compounds of formula (I) are cleaved and form one or more organoleptic and/or antimicrobial compounds.
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- Precursors for fragrant ketones and fragrant aldehydes
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The present invention refers to fragrance precursors of formula I for a fragrant ketone of formula II and one or more fragrant aldehydes or ketones of formula III and IV, These fragrance precursors are useful in perfumery, especially in the fine and functional perfumery.
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- Beta-ketoester compounds
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The beta-ketoesters of formula I are useful as precursors for organoleptic compounds, especially for flavors, fragrances and masking agents and antimicrobial compounds.
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- Ketone precursors for organoleptic compounds
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The invention discloses ketones of formula I: wherein, Y is an optionally substituted alkyl, cycloalkyl, or cycloalkylalkyl, wherein each alkyl group is straight or branched and each alkyl and cycloalkyl group is saturated or unsaturated; R1is hydrogen or a C1-6alkyl group that is substituted, saturated or unsaturated, straight or branched; A is a chromophoric substituted aromatic ring or ring system; n is an integer; and with the proviso that formula I is not 2-ethoxy-1-phenyl-ethanone. These compositions are useful for the delivery of organoleptic compounds, especially of flavors, fragrances, masking agents and antimicrobial compounds.
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- Raney nickel: An efficient reagent to achieve the chemoselective hydrogenation of α,β-unsaturated carbonyl compounds
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Raney Nickel is an effective reagent to achieve the chemoselective reduction of conjugated olefins in σ,β-unsaturated carbonyl compounds that also contain isolated double bonds. Its use is also compatible with a variety of other functional groups.
- Barrero, Alejandro F.,Alvarez-Manzaneda,Chahboun, Rachid,Meneses
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p. 1663 - 1666
(2007/10/03)
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- Cu/SiO2: An improved catalyst for the chemoselective hydrogenation of α,β-unsaturated ketones
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Cu/SiO2 can be conveniently used for the quantitative hydrogenation of conjugated enones to saturated ketones, also when another olefinic bond is present in the molecule, under very mild conditions. Molecular H2 or 2-propanol can be used as hydrogen source.
- Ravasio, Nicoletta,Antenori, Marisa,Gargano, Michele,Mastrorilli, Piero
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p. 3529 - 3532
(2007/10/03)
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- Pd/AlPO4 CATALYSED SELECTIVE LIQUID-PHASE HYDROGENATION OF β-IONONE INTO CIS-DIHYDROIONONE
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The liquid-phase hydrogenation of β-ionone 1 was carried out at 302 K with 0.205 MPa of initial hydrogen pressure in methanol on Pd/AlPO4 catalyst (2-3 percent).The cis-dihydroionone 2 was obtained with a 83 percent selectivity which is independent of the degree of conversion.The reaction rate depends on the chloride concentration in the catalyst and the rection selectivity is a function of the support of the Pd.According to the Langmuir-Hinshelwood kinetic models and the Horiuti-Polanyi type mechanism, the reaction order with respect to β-ionone concentration is negative and of one half order with respect to the hydrogen pressure.The comparison with results obtained over Pd/C catalyst and those obtained in the catalytic hydrogenation of α-ionone suggests that the catalytic hydrogenation of β-ionone could take place on two different active sites of the Pd.
- Bouchry, Naima,Aune, Jean-Pierre,Rais, Taoufiq
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p. 439 - 448
(2007/10/02)
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- The liquid-phase catalytic hydrogenation of β-ionone has been carried out using Pd/C catalyst
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The reaction products obtained upon reduction of β-ionone were cis-dihydroionone, dihydro-β-ionone, tetrahydroionone, dihydro-α-ionone and small quantities of alcohols.Selectivity towards each product is not affected by the reaction conditions such as temperature (261-318 K), hydrogen pressure (0.11-0.53 MPa), β-ionone concentration (0.28-2.45 M) and the nature of the solvent.Under our working conditions, the order of the reaction with respect to the substrate is negative and the process is half an order in hydrogen pressure.The catalytic hydrogenation of α-ionone has been carried out in the same conditions and the selectivity of dihydro-α-ionone reaches 76percent.It appears that the conjugate ability of the system in β-ionone is responsible for the selectivity to the cis-dihydroionone (66percent) obtained during the catalytic hydrogenation of the second product. - Key words: catalytic hydrogenation / β-ionone / α-ionone / selectivity / Pd/C / apparent activation energy
- Bouchry, Naima,Aune, Jean-Pierre,Coudurier, Gisele,Rais, Taoufiq
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p. 243 - 248
(2007/10/02)
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- Selective 1,4-Reduction of Conjugated Aldehydes and Ketones in the Presence of Unconjugated Aldehydes and Ketones with Sodium Dithionite
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Chemoselective 1,4-reduction of α,β-unsaturated aldehydes or ketones has been achieved with sodium dithionite in H2O/dioxane at 50 deg C in the presence of unsaturated (nonconjugated) and saturated aldehydes or ketones.
- Dhillon, Ranjit S.,Singh, Rupinder P.,Kaur, Daljit
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p. 1107 - 1108
(2007/10/02)
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- BIOTRANSFORMATION OF α- AND β-IONONES BY IMMOBILIZED CELLS OF NICOTIANA TABACUM
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Immobilized cells of Nicotiana tabacum reduced the carbon-carbon double bond adjacent to the carbonyl group and then the carbonyl group itself of the dienone compounds, α-ionone and β-ionone: In addition, the selectivity for the reduction of the double bond adjacent to the carbonyl group could be enhanced by performing the biotransformation in medium with a pH near the optimal pH of the enone reductase which specifically catalyses the reduction of the α,β-unsaturated double bond of s-trans-enones. - Key words: Nicotiana tabacum; Solanaceae; plant cell cultures; immobilized cells; dienone; β-ionone; α-ionone; biotransformation.
- Tang, Yi-Xiong,Suga, Takayuki
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p. 737 - 740
(2007/10/02)
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- Internal Nucleophilic Termination in Biomimetic Acid Mediated polyene Cyclizations: Stereochemical and Mechanistic Implications. Synthesis of (+/-)-Ambrox and Its Diastereoisomers
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Treatment of 10 structurally releted trienols and dienols 5-8 with an excess of fluorosulfonic acid in 2-nitropropane at -90 deg C afforded, in 74-87percent yield, diastereoisomeric mixtures of the odoriferous norlabdane oxides 9-15 ((-)-9 (Ambrox) is a naturally occuring ambergris odorant).These tranformations represent examples of efficientbiomimetic acid-mediated cyclizations in which the hydroxyl group serves as the internal nucleophilic terminator.The stereochemical outcome of these kinetically controlled processes has been analysed in detail, and mechanistic hypotheses consistent with the results have been proposed.For the four acyclic trienols 5, the major reaction pathway can be rationalized by a totally synchronous process involving three internal anti additions via chair or skew-boat conformations of the nascent cyclohexane rings.An alternative explanation postulates a nonsynchronous process in which ring closure to an intermediate cyclohexyl cation is followed by rapid cyclization, directed by a strong kinetic preference for equatorial C-C and C-O bond formation.In contrast, for the monocyclic dienols 6-8 only a nonsynchronous process, involving prior protonation of the cyclohexenyl bond, is fully consisitent with the results.In the nonsynchronous processes, the orientation of the side chain vicinal to the cyclohexyl cation directs the stereochemical course of the cyclization.For the acyclic trienols, this factor is predetermined by the configuration of the C(7)=C(8) bond, whereas, for the monocyclic dienols, this orientation is determined by the stereoselective axial protonation of the cyclohexenyl bond in 6, or by the distribution of cyclohexene and cyclohexane conformers in 7 and 8, respectively.In the cases studied, it is clear that conformational inversion of the six-membered ring is slower than cyclization and thus ensures that an equatorial side chain leads to a trans A/B ring junction in the cyclization product, whereas an axial side chain affords a cis A/B ring junction.
- Snowden, Roger L.,Eichenberger, Jean-Claude,Linder, Simon M.,Sonnay, Philippe,Vial, Christian,Schulte-Elte, Karl H.
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p. 955 - 960
(2007/10/02)
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- SYNTHESIS OF DIHYDROPALLESCENSIN D VIA MANGANESE(III) MEDIATED CYCLIZATION OF AN OLEFINIC β-KETO ESTER
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Free radical oxidative cyclization of keto ester 5 with manganese(III) acetate and copper(II) acetate gave bicyclodecanone 6 which was transformed into the furanosesquiterpene dihydropallescensin D.
- White, James D.,Somers, Todd C.,Yager, Kraig M.
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- CATALYTIC HYDROGENATION OF OLEFINS IN BIPHASIC WATER-LIQUID SYSTEM
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Cyclic and linear olefins and polyenes with or without functional groups are hydrogenated under very mild reaction conditions.Emphasis is put on the advantages of this method which requires no solvent and a water-soluble non air-sensitive catalyst.
- Larpent, Chantal,Dabard, Renee,Patin, Henri
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p. 2507 - 2510
(2007/10/02)
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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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p. 4603 - 4610
(2007/10/02)
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- Sesquiterpenoid Constituents of the Liverwort, Ptychanthus striatus (LEHM. et LINDENB.) NEES
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Four sesquiterpenoids, striatene, striatol, β-monocyclonerolidol and ptychanolide, were isolated from the liverwort Ptychanthus striatus (LEHM. et LINDENB.)NEES. Their structures have been established by spectroscopic analysis and chemical transformation. Three of them, striatene, striatol and β-monocyclonerolidol, are interesting in terms of the evolution of the liverwort fom the algae.
- Takeda, Reiji,Naoki, Hideo,Iwashita, Takashi,Mizukawa, Kosei,Hirose, Yoshio,et al.
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p. 1125 - 1132
(2007/10/02)
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- STRUCTURAL AND ABSOLUTE CONFIGURATIONAL STUDIES OF STRIATENE, STRIATOL AND β-MONOCYCLONEROLIDOL, THREE SESQUITERPENOIDS FROM THE LIVERWORT PTYCHANTHUS STRIATUS (LEHM. ET LINDBEMB.) NEES
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Three new sesquiterpenoids, striatene, striatol and β-monocyclonerolidol, were isolated from the liverwort Ptychanthus striatus (Lehm. et Lindemb.) Nees.Their structures have been established by spectroscopic analysis and chemical transformation.These compounds are interesting in terms of the evolution of the liverwort from algae.
- Takeda, Reiji,Mori, Reiko,Hirose, Yoshio
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p. 1625 - 1628
(2007/10/02)
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- Active Metals from Potassium-Graphite. Air-Oxidized Nickel-Graphite as a New Selective Hydrogenation Catalyst
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Air exposure of Ni-Gr1 affords a modified, less active hydrogenation catalyst (air-oxidized nickel-graphite, Ni-Gr2), owing to a partial oxidation of the metal, which is able to reduce carbon-carbon, carbon-oxygen, and carbon-nitrogen multiple bonds under 30 atm of hydrogen in the temperature range 30-130 deg C.A remarkable bond selectivity in the hydrogenation of polyfunctional molecules such as unsaturated carbonyl compounds and β-diketones is observed.
- Savoia, Diego,Tagliavini, Emilio,Trombini, Claudio,Umani-Ronchi, Achille
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p. 5344 - 5348
(2007/10/02)
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