- An Approach to the Syntheiss of (-)-Lipstatin by Wittig Reaction and Lewis Acid-promoted Cycloaddition
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The β-lactone moiety of (-)-lipstatin 1, a potent inhibitor of pancreatic lipase, is prepared via a Lewis acid-promoted cycloaddition between hexyltrimethylsilyl ketene 3 and the (Z,Z)-dienic aldehyde 4, obtained from hexenal by two stereoselective Wittig reactions.
- Pons, Jean-Marc,Pommier, Agnes,Lerpiniere, Joan,Kocienski, Philip
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- Soybean lipoxygenase and horseradish peroxidase catalysed asymmetric oxidation-reduction sequence for the synthesis of chiral (Z,E) diene-diols
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Unnatural synthetic substrates with a properly spaced prosthetic modifier having non-ionic hydroxy terminus undergoes soybean lipoxygenase catalysed asymmetric peroxidation followed by horseradish peroxidase induced reduction affords (Z, E)-dienediol in high enantiomeric excess.
- Yadav,Nanda,Bhaskar Rao
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- Exploitation of a Multienzymatic Stereoselective Cascade Process in the Synthesis of 2-Methyl-3-Substituted Tetrahydrofuran Precursors
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Enantiopure 2-methyl-3-substituted tetrahydrofurans are key precursors of several biologically active products (drugs, flavors, and agrochemicals). Thus, a stereocontrolled and efficient methodology for the obtainment of these synthons is highly desirable. We exploited a two-step multienzymatic stereoselective cascade reduction of α-bromo-α,β-unsaturated ketones to give the corresponding bromohydrins in good yields, with high ee and de values. The cascade process is catalyzed by an ene-reductase and an alcohol dehydrogenase. Further manipulations of these bromohydrins, by two diastereodivergent routes, allowed the preparation of the tetrahydrofuran synthons. One route is based on a lipase catalyzed cleavage of the protecting group. The second route is characterized by a camphor sulfonic acid mediated isomerization of a β-hydroxyepoxide to give the tetrahydrofuran-2-ol. Finally, the synthesis of the most odorous and pleasant stereoisomer of the roasted meat aroma, i.e., (2S,3R)-2-methyl-3-thioacetate tetrahydrofuran, is reported as well.
- Brenna, Elisabetta,Crotti, Michele,Gatti, Francesco G.,Marinoni, Ludovico,Monti, Daniela,Quaiato, Sara
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- A new practical method for the preparation of [3H6]-leukotrienes C4 and D4
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A new method for the synthesis of highly deuterated or tritiated leukotrienes was developed. The higher reactivity of a terminal alkene compared to a 1,2-disubstituted one permitted the selective deuteration or tritiation of the diyne 14,15,19,19,20,20-hexadehydro LTC4 triester 1. After hydrolysis. LTC4 was obtained in 36% overall yield. An average of seven deuterium or tritium atoms was incorporated and the specific activity of the tritiated LTC4 was greater than 180 Ci/mmol. 1 was obtained from the addition of glutathione to 14,15,19,19,20,20-hexadehydro LTA4 ethyl ester which was the product of a Wittig reaction between (3,8-nonanediyn-1-yl)triphenylphosphonium iodide and 5(S), 6(S), 7(E), 9(E) ethyl 5,6-epoxy-11-oxo-7,9-undecadienoate.
- Belley,Gareau,Zamboni,Ahern,Hong
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- NbCl5-Mg reagent system in regio-and stereoselective synthesis of (2Z)-alkenylamines and (3Z)-alkenylols from substituted 2-alkynylamines and 3-alkynylols
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The reduction of N,N-disubstituted 2-alkynylamines and substituted 3-alkynylols using the NbCl5 –Mg reagent system affords the corresponding dideuterated (2Z)-alkenylamine and (3Z)-alkenylol derivatives in high yields in a regio-and stereoselective manner through the deuterolysis (or hydrolysis). The reaction of substituted propargylamines and homopropargylic alcohols with the in situ generated low-valent niobium complex (based on the reaction of NbCl5 with magnesium metal) is an efficient tool for the synthesis of allylamines and homoallylic alcohols bearing a 1,2-disubstituted double bond. It was found that the well-known approach for the reduction of alkynes based on the use of the TaCl5-Mg reagent system does not work for 2-alkynylamines and 3-alkynylols. Thus, this article reveals a difference in the behavior of two reagent systems—NbCl5-Mg and TaCl5-Mg, in relation to oxygen-and nitrogen-containing alkynes. A regio-and stereoselective method was developed for the synthesis of nitrogen-containing E-β-chlorovinyl sulfides based on the reaction of 2-alkynylamines with three equivalents of methanesulfonyl chloride in the presence of stoichiometric amounts of niobium(V) chloride and magnesium metal in toluene.
- Dzhemilev, Usein M.,Gabdullin, Azat M.,Kadikova, Rita N.,Mozgovoj, Oleg S.,Ramazanov, Ilfir R.
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supporting information
(2021/07/02)
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- Catalytic Regio- and Enantioselective Oxytrifluoromethylthiolation of Aliphatic Internal Alkenes by Neighboring Group Assistance
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Chiral selenide-catalyzed oxytrifluoromethylthiolation of aliphatic internal alkenes by a formally intermolecular strategy is disclosed, affording CF3S 1,3-amino alcohol and 1,3-diol derivatives with high regio-, enantio-, and diastereoselectivities. The reactions are promoted by a neighboring imide or ester group on substrates via a six-membered ring transition state. This assistance strategy is also successfully applied to the regio- and diastereoselective oxyhalofunctionalization of internal alkenes and the conversion of alkynes.
- Xu, Jia,Zhang, Yuanyuan,Qin, Tian,Zhao, Xiaodan
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p. 6384 - 6388
(2018/10/09)
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- Chemo- and Enantioselective Intramolecular Silver-Catalyzed Aziridinations
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Asymmetric nitrene-transfer reactions are a powerful tool for the preparation of enantioenriched amine building blocks. Reported herein are chemo- and enantioselective silver-catalyzed aminations which transform di- and trisubstituted homoallylic carbamates into [4.1.0]-carbamate-tethered aziridines in good yields and with ee values of up to 92 %. The effects of the substrate, silver counteranion, ligand, solvent, and temperature on both the chemoselectivity and ee value were explored. Stereochemical models were proposed to rationalize the observed absolute stereochemistry of the aziridines, which undergo nucleophilic ring opening to yield enantioenriched amines with no erosion in stereochemical integrity.
- Ju, Minsoo,Weatherly, Cale D.,Guzei, Ilia A.,Schomaker, Jennifer M.
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p. 9944 - 9948
(2017/08/08)
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- Chiral Selenide-Catalyzed Enantioselective Construction of Saturated Trifluoromethylthiolated Azaheterocycles
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An indane-based, bifunctional, chiral selenide catalyst has been developed. The new catalyst is efficient for the enantioselective synthesis of saturated azaheterocycles possessing a trifluoromethylthio group. The desired products were obtained in good yields with high diastereo- and enantioselectivities.
- Luo, Jie,Liu, Yannan,Zhao, Xiaodan
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supporting information
p. 3434 - 3437
(2017/07/15)
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- A containing halogen light active 2 - oxo - 1, 3 - oxazine compounds and its preparation method and application
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The invention discloses a 2-carbonyl-1,3-oxazine compound and a preparation method therefor and application thereof. The structural formula of the 2-carbonyl-1,3-oxazine compound is shown in a formula II. The preparation method comprises: carrying out a reaction on a compound shown in a formula I and N-bromoacetamide (or 1,3-dibromo-5,5-dimethyl hydantoin) under the action of a scandium trifluoromethanesulfonate/monophosphine ligand. The photoactive 2-carbonyl-1,3-oxazine compound provided by the invention can be used for conveniently obtaining compounds containing 1,3-hydroxylamine structures and functionalized heterocyclic compounds through further conversion reactions, and meanwhile, a bromine atom can be introduced into the reaction. The functional groups can be further converted. Other functional groups are introduced, so that the compound has huge application value. According to the method provided by the invention, raw materials are easily synthesized, the reaction condition is mild, the operation is simple and convenient, the region selectivity is high, the enantioselectivty can reach up to over 99%, and the output reaches up to 72%. The formulae are shown in the description.
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Paragraph 0095-0098
(2017/08/23)
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- COMPLEX CATALYSTS BASED ON AMINO-PHOSPHINE LIGANDS FOR HYDROGENATION AND DEHYDROGENATION PROCESSES
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The present application discloses novel PWNN and PWNWP metal catalysts for organic chemical syntheses including hydrogenation (reduction) of unsaturated compounds or dehydrogenation of substrates. The range of hydrogenation substrate compounds includes esters, lactones, enals, enones, enolates, oils and fats, resulting in alcohols, enols, diols, and triols as reaction products. The catalysts of current application can be used to catalyze a hydrogenation reaction under solvent free conditions. The present catalysts also allow the hydrogenation to proceed without added base, and it can be used in place of the conventional reduction methods employing hydrides of the main-group elements. Furthermore, the catalysts of the present application can catalyze a dehydrogenation reaction under homogenous and/or acceptorless conditions. As such, the catalysts provided herein can be useful in substantially reducing cost and improving the environmental profile of manufacturing processes for a variety of chemicals.
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Page/Page column 38; 39
(2014/09/29)
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- From esters to alcohols and back with ruthenium and osmium catalysts
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There and back again: Hydrogenation of esters and the reverse reaction of dehydrogenative coupling of alcohols are efficiently catalyzed by dimeric complexes of Ru and Os under neutral conditions. The Os dimer (see picture) is an outstanding catalyst for the hydrogenation of alkenoates and triglycerides, and allows production of fatty alcohols from olive oil. This complex converts ethanol into ethyl acetate and hydrogen under reflux. Copyright
- Spasyuk, Denis,Smith, Samantha,Gusev, Dmitry G.
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supporting information; experimental part
p. 2772 - 2775
(2012/05/20)
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- tert-butyl ethers: Renaissance of an alcohol protecting group. Facile cleavage with cerium(III) chloride/sodium iodide
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The tert-butoxy derivative is one of the most underused alcohol protecting groups. After having developed an easy and useful protocol for its introduction, we offer here a simple procedure for its removal by treatment with anhydrous CeCl3 and NaI in CH3CN. The procedure led to the successful cleavage of aliphatic and aromatic tert-butyl ethers and was compatible with various other functionalities and protecting groups present in the molecule.
- Bartoli, Giuseppe,Bosco, Marcella,Carlone, Armando,Locatelli, Manuela,Marcantoni, Enrico,Melchiorre, Paolo,Sambri, Letizia
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p. 905 - 910
(2007/10/03)
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- METHOD FOR THE ADDITION OF FORMALDEHYDE TO OLEFINS
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The invention relates to a method for the manufacture of non-saturated homoallyl alcohols and their formiates by the conversion of formaldehyde with an olefin or an olefin mixture.
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- Enzymatic asymmetric hydroxylation of unnatural substrates with soybean lipoxygenase
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Surrogate substrates mimicking the natural substrate (linoleic acid) bearing a spacing prosthetic group with a non-ionic hydroxyl terminus undergo asymmetric hydroxylation with soybean lipoxygenase. The prosthetic modifier supplies the missing structural features needed for enzymatic recognition and controls the regiochemical outcome of the reaction by its high hydrophobic content. The effect of pH on the regiochemistry clearly shows that all the substrates can arrange themselves at the active site of soybean lipoxygenase in only one orientation leading to formation of hydroperoxides by oxygenation at the ω-6 carbon.
- Yadav,Nanda,Rao
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p. 2129 - 2135
(2007/10/03)
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- The first total synthesis of (-)-lipstatin
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A key step in the first total synthesis of the potent pancreatic lipase inhibitor (-)-lipstatin (1) is a diastereoselective Lewis acid-promoted [2 + 2] cycloaddition reaction between n-hexyl(trimethylsilyl)ketene (4) and (R)-(-)-(Z,Z)-3-[(tert-butyldimethylsilyl)oxy]-5,8-tetradecadienal (3), which is prepared from dimethyl (S)-(-)-malate.
- Pommier,Pons,Kocienski
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p. 7334 - 7339
(2007/10/03)
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- REDUCTION OF α-ALKYNYL EPOXIDES
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The catalytic hydrogenation of 2-(1-heptynyl)oxirane leads preferentially to 3(Z)-nonen-1-ol, whereas the reduction of this epoxide with lithium in ethylamine gives 3(E)-nonen-1-ol.In both cases the main products are accompanied by the isomeric 2-nonen-1-ols.
- Vasil'ev, A. A.
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- Synthesis of 19(RS)-O-TBDMS-LTA4 methyl ester
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The first convergent synthesis of methyl 19(RS)-t-butyldimethylsilyloxy-5(S),6(S)-epoxy-icosa-7(E),9(E),11(Z),14(Z)-tetraenoate (19(RS)-O-TBDMS-LTA4 1) is described, using a Wittig reaction between a C1-C11 chiral epoxydienal (from (-)-2-deoxy-D-ribose as starting material) and an (ω - 1) functionalized phosphorus ylide, which was obtained by a reaction of alkyl bromide and lithium alkynylide.This strategy is sufficiently general and could allow to synthesize other analogues giving new haptens.Key Words: leukotriene A4 / ω - 1 functionalized phosphonium ylide
- Pastouret, A.,Vidal, J. P.,Durand, T.,Girard, J. P.,Rossi, J. C.
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p. 206 - 213
(2007/10/02)
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- Dispersion of Rh/Cu in a Sol-Gel Matrix. Highly Chemo- and Stereoselective Catalyst for the Reduction of Alkynes to Z-Alkenes
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Treatment of hydrated RhCl3 and Cu(NO3)2 in THF and H2O with triethoxysilane affords a highly chemo- and stereoselective catalyst system for the reduction of alkynes to Z-alkenes while alkyl-NO2, aryl-NO2, N-carbobenzyloxy, hydroxy, ester, enoate, benzyloxy, alkyl bromide, aryl bromide, and enone moieties remain unaffected.
- Tour, James M.,Pendalwar, Shekhar L.,Kafka, Cynthia M.,Cooper, Joel P.
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p. 4786 - 4787
(2007/10/02)
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- COMPOUNDS WITH GREEN PLANT FRAGRANCE. IV. SUBSTITUTED CIS-3-ALKEN-1-OLS
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Syntheses are reported for leaf alcohol analogs, namely, substituted cis-3-alken-1-ols.Many of these compounds have green plant fragrance similar to that of a leaf alcohol standard (cis-3-hexen-1-ol).
- Vasil'ev, A. A.,Cherkaev, G. V.,Nikitina, M. A.
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p. 220 - 225
(2007/10/02)
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- A Stereoselective Synthesis of Trisubstituted Alkenes. Part 1. Nickel-catalysed Coupling of Grignard Reagents with 5-Alkyl-2,3-dihydrofurans
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5-Alkyl-2,3-dihydrofurans 3a-j prepared by the alkylation of 5-lithio-2,3-dihydrofuran 2 with primary alkyl bromides and iodides, undergo Ni(0)-catalysed coupling with Grignard reagents to give homoallylic alcohols.The yield and stereoselectivity depend on the structure of the Grignard reagent with the best results being obtained with long chain primary Grignard reagents and Grignard reagents lacking β-hydrogens (Me, Ph, Me3SiCH2). 5-(1-Hydroxyalkyl)-2,3-dihydrofurans 20 and 21 are poor substrates for the coupling reaction.Mechanisms are proposed for the coupling as well as competing reduction and isomerisation reactions.
- Kocienski, Philip J.,Pritchard, Martin,Wadman, Sjoerd N.,Whitby, Richard J.,Yeates, Clive L.
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p. 3419 - 3430
(2007/10/02)
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- One-Pot Conversions of (Silylmethyl)cyclopropanes to Homoallylic Alcohols and 1,4-Diols Based on Haloborane-Induced Ring Opening
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The reactions of (silylmethyl)cyclopropanes with haloboranes, such as BBr3 and BHBr2, result in desilylative ring opening to give homoallylboranes and boracyclopentanes, respectively.Coupled with subsequent oxidation procedure, these reactions provide ready access to homoallylic alcohols and 1,4-diols.
- Ryu, Ilhyong,Hirai, Akira,Suzuki, Haruhisa,Sonoda, Noboru,Murai, Shinji
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p. 1409 - 1410
(2007/10/02)
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- Synthesis of rigidified arachidonic acid analogues
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The synthesis of eight arachidonic acid analogues, rigidified by bridging the 7- and 10- or the 10-and 13-bis-allylic positions, is described.
- Stoller,Mioskowski,Millet,Sepulchre,Bellamy
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p. 5035 - 5038
(2007/10/02)
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- Synthesis of (+/-)-Dictyoprolene through (Z)-3-Nonenol, A Pheromonal Component of Anastrepha ludens
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Synthesis of (+/-)-dictyoprolene has been achieved through the transformation of (Z)-3-nonenol, a pheromonal component of female fruit flies (Anastrepha ludens) via three steps.
- Vig, O. P.,Kad, G. L.,Sabharwal, Arun,Sharma, Sanjiv,Dogra, Vijay
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- An Efficient and Stereoselectice Synthesis of Homoallykic Alcohols via Nickel-catalysed Coupling of 5-Alkyl-2,3-dihydrofurans with Grignard Reagents
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The low-valent nickel-catalysed coupling of Grignard reagents with 5-alkyl-2,3-dihydrofurans is an efficient and stereoselective method for synthesising homoallylic alcohols provided appropriate care is taken in the workup.
- Wadman, Sjoerd,Whitby, Richard,Yeates, Clive,Kocienski, Philip,Cooper, Kelvin
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p. 241 - 243
(2007/10/02)
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- Reversibility of a Wittig Intermediate derived from a Triphenylphosphonium Ylide and an Aliphatic Aldehyde
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Wittig-reaction intermediates derived from hexanal and (γ-oxidopropylidene)triphenylphosphorane, (1), are freely reversible, as indicated by significant quantities of cross-over products from a second aldehyde (octanal); such a result may account for anomalously enhanced E stereoselectivity in the reaction of γ- and β-oxido ylides with aliphatic aldehydes.
- Reitz, Allen B.,Maryanoff, E.
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p. 1548 - 1549
(2007/10/02)
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- Enantiospecific syntheses of leukotrienes C4, D4 and E4 and [14,15-3H2]leukotriene E4 dimethyl ester
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A 'chiral-pool' approach was employed to synthesize various leukotrienes (slow-reacting substance of anaphylaxis, SRS-A) enantiospecifically. The pivotal (S,S)-trans-epoxy alcohol 9 was prepared by efficient and facile routes starting from erythorbic acid (D-araboascorbic acid, 13). This epoxide could also be produced starting from D-glucose. The epimeric (S,R)-cis-epoxide 38 was obtained utilizing L-tartaric acid as the chiral starting material. Elaboration of 9 into leukotriene A4 methyl ester (5) and the potassium salts of leukotrienes C4 (4a), D4 (4b), and E4 (4c) was accomplished by standard methods. These salts exhibited potent contractile activities in the in vitro guinea pig ileum assay. Reduction of 14,15-dehydroleukotriene A4 methyl ester (44) with tritium gas gave [14,15-3H2]-5 and subsequently the dimethyl ester of [14,15-3H2]leukotriene E4 having a high specific activity of 40 Ci/mmol.
- Cohen,Banner,Lopresti,et al.
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p. 3661 - 3672
(2007/10/02)
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- STEREOCHEMICAL OBSERVATIONS ON THE WITTIG REACTION OF OXIDO PHOSPHONIUM YLIDES WITH ALDEHYDES
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The reaction of aldehydes with oxido ylides shows a dramatic dependence of alkene stereochemistry on the distance between oxygen and phosphorus atoms; ylides with proximal O and P atoms favor production of E alkenes.The high E stereoselectivity with γ-oxido ylides is not mainly attributable to intramolecular proton-exchange in a Wittig intermediate.
- Maryanoff, Bruce E.,Reitz Allen B.,Duhl-Emswiler, Barbara A.
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p. 2477 - 2480
(2007/10/02)
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- DIMETHYLALUMINUM CHLORIDE CATALYZED ENE REACTIONS OF ALDEHYDES.
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Dimethylaluminum chloride, which is a mild Lewis acid and a proton scavenger, catalyzes the ene reactions of aliphatic and aromatic aldehydes with alkenes containing a disubstituted vinylic carbon. Proton-initiated rearrangements do not occur, since the alcohol-Lewis acid complex formed in the ene reaction reacts rapidly to give methane and a nonacidic aluminum alkoxide. Formaldehyde and excess Me//2AlCl give good yields of ene adducts with all types of alkenes. With 1 equiv of Me//2AlCl, formaldehyde and mono- and 1,2-disubstituted alkenes give gamma -chloro alcohols resulting from cis addition of chlorine and hydroxymethyl groups to the double bond. This work is pertinent to the synthesis of alcohols.
- Snider,Rodini,Kirk,Cordova
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p. 555 - 563
(2007/10/02)
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- THE SYNTHESIS OF A LEUKOTRIENE WITH SRS-LIKE ACTIVITY
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The synthesis and biological charachteristics of an SRS-like leukotriene are described.
- Rokach, Joshua,Girard, Yves,Guindon, Yvan,Atkinson, Joseph G.,Larue, Marie,et al.
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p. 1485 - 1488
(2007/10/02)
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- THE SYNTHESIS OF NATURALLY OCCURRING 4-ALKYL- AND 4-ALKENYL-γ-LACTONES USING THE ASYMMETRIC REDUCING AGENT B-3-PINANYL-9-BORABICYCLONONANE
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4-Hydroxy-2-alkynoates of high enantiomeric purity, available from the reduction of the corresponding ketones with B-3-pinanyl-9-BBN, are converted to 4-substituted-γ-lactones found in beetle and deer pheromones.
- Midland, M. Mark,Tramontano, Alfonso
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p. 3549 - 3552
(2007/10/02)
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