Showing papers on "Enone published in 1997"
TL;DR: In this article, the authors used (2 S )-L -prolines to catalyze the asymmetric Michael addition of nitroalkanes to prochiral acceptors.
100 citations
TL;DR: The cdc25A protein phosphatase inhibitor dysidiolide has been synthesized enantioselectively, starting from the enantiomerically pure ketal enone 2 and using a cationic rearrangement as the key step to produce the fully substituted bicyclic core of the natural product.
Abstract: The cdc25A protein phosphatase inhibitor dysidiolide (1) has been synthesized enantioselectively, starting from the enantiomerically pure ketal enone 2 and using a cationic rearrangement as the key step to produce the fully substituted bicyclic core of the natural product. Once the central portion of 1 was established, elaboration of the side chains was accomplished expediently via steps that included (1) vinyl cuprate displacement of an iodide to complete the C-1 side chain, (2) a highly diastereoselective oxazaborolidine-catalyzed (CBS) reduction to form carbinol 11, and (3) photochemical oxidation of 11 to generate the γ-hydroxybutenolide functionality of 1. Additionally, this synthesis proves the absolute stereochemistry of dysidiolide (1).
98 citations
TL;DR: In this paper, the amino alcohols were employed as chiral ligands in the nickel catalyzed conjugate additions of diethylzinc to chalcone and cyclohexenone as model substrates.
Abstract: Several novel tri- and tetradentate amino alcohol ligands, all derived from (+)-camphor, have been synthesized by using specific N -alkylation procedures. The amino alcohols were employed as chiral ligands in the nickel catalyzed conjugate additions of diethylzinc to chalcone and cyclohexenone as model substrates. For the acyclic enone enantioselectivities up to 83% were achieved.
45 citations
TL;DR: The formation of the enone 6 indicates that arteflene fragments to a non-stabilised carbon-centred radical, which is proposed to mediate the potent antimalarial activity of 4.
36 citations
TL;DR: Two highly stereoselective and efficient sequencial 1,4-additions to enone systems, derived from d-(−)-quinic acid, are the key to the synthesis of (+)-eutypoxide B.
Abstract: The enantioselective synthesis of (+)-eutypoxide B, a metabolite isolated from the culture medium of the fungus Eutypa lata, is described. Two highly stereoselective and efficient sequencial 1,4-additions to enone systems, derived from d-(−)-quinic acid, are the key to the synthesis. The synthesis of a diastereoisomer of (+)-eutypoxide B, was also accomplished.
33 citations
TL;DR: The first synthesis of a functionalized tricyclic skeleton of vinigrol was described in this paper, which involved an anionic oxy-Cope rearrangement of bicyclic allylic alcohol.
Abstract: The first synthesis of a functionalized tricyclic skeleton of vinigrol is described. The key step involved an anionic oxy-Cope rearrangement of bicyclic allylic alcohol 18, readily prepared by highly stereoselective addition of vinyl magnesium chloride to the hydroxy enone 15b. Introduction of the tertiary hydroxy group at carbon 8a was achieved by an unexpected hydration of 30 with aqueous trifluoroacetic acid.
33 citations
TL;DR: The asymmetric synthesis of (+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740) has been accomplished starting from the readily available enantiomerically pure cyclopentenone 4.
Abstract: The asymmetric synthesis of (+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740) 1, a potent and selective group 2 mGluR agonist, has been accomplished starting from the readily available enantiomerically pure cyclopentenone 4. Thus, cyclopropanation with ethyl(dimethylsulfuranylidene)acetate generated in situ with DBU, followed by deketalization gave rise to the dihydroxy bicyclic ketone 9. After protecting the ketone as 1,3-dioxolane and its transformation to the orthoformate 11, this was pyrolytically deoxygenated in a sealed tube to the bicyclic enone 13. The synthesis was completed after hydrogenation, stereoselective Bucherer-Bergs reaction and hydantoin hydrolysis, yielding LY354740 (+)-1 with an e.e. ≥98%.
32 citations
TL;DR: Asymmetric synthesis of L-carbocyclic nucleosides, (+)-β-L-aristeromycin (11 ) and its thymine analog (12 ) was accomplished as discussed by the authors.
29 citations
TL;DR: The enaminone 4, prepared from (2S)-pyroglutamic acid, has been found to react in an apparent 1,4-manner with DIBAL and Grignard reagents to afford a variety of alkylidene derivatives 8 which, except for the vinyl derivatives 8e, are formed only as the (E)-isomers as discussed by the authors.
Abstract: The enaminone 4, prepared from (2S)-pyroglutamic acid, has been found to react in an apparent 1,4-manner with DIBAL and Grignard reagents to afford a variety of alkylidene derivatives 8 which, except for the vinyl derivatives 8e, are formed only as the (E)-isomers. Three of these have been converted to the 4-alkylideneglutamic acids, 1, 2 and 3, which are identical to known natural products, the synthesis confirming 2 and 3 as the E-isomers. Catalytic reduction of the 4-alkylidenepyroglutamate derivatives 8 is stereospecific and affords an effective route to (2S,4S)-4-alkylglutamic acids and (2S,4S)-4-alkylprolines. Cuprate addition to the enone 5 affords access to the (2S,4R)-epimer 15 and carbene addition allows cyclopropylglutamic acids 32 and 33 to be prepared.
28 citations
TL;DR: Iso[4]-levuglandin E2 (iso[ 4]-LGE2, 5-acetyl-6-formyl-9-hydroxy-7(E),11(Z)-heptadecadienoic acid) is a structural isomer of LGE2 that was postulate to be generated during autoxidation of arachidonic acid or arachidonate esters as mentioned in this paper.
Abstract: Iso[4]-levuglandin E2 (iso[4]-LGE2, 5-acetyl-6-formyl-9-hydroxy-7(E),11(Z)-heptadecadienoic acid) is a structural isomer of levuglandin E2 (8-acetyl-9-formyl-12-hydroxy-5(Z),10(E)-heptadecadienoic acid) that we postulate to be generated during autoxidation of arachidonic acid or arachidonate esters. To facilitate detection and identification of iso[4]-LGE2 in biological samples, a succinct total synthesis was developed that depends on conjugate addition of a higher order vinyl cyanocuprate to a γ-alkoxy enone to provide a key carbon−carbon bond-forming step. Bismethoxime pentafluorobenzyl ester trimethylsilyl ether derivatives of LGE2 and iso[4]-LGE2 were prepared and shown to be suitable for mass spectral identification of these highly oxidized lipids.
26 citations
TL;DR: In this article, an optically active 1,3-disubstituted allene was used for enantioselective intramolecular allene/enone photocycloadditions.
TL;DR: In this article, the stereoselective synthesis of a bicyclic ring system related to Neocarzinostatin and Kedarcidin Chromophores is described.
TL;DR: In this article, a two-step 2+2-photocycloaddition with substituted alkenes was analyzed using frontier molecular orbital (FMO) methods using molecular orbital energies and coefficients of corresponding species calculated by PM3-CI method.
TL;DR: In this paper, new derivatives of 3-oxoolean-1-en-28-oic acid and 3oxours-1,9-dien-28 oic acid were synthesized and showed significant inhibitory activity against interferon-γ-induced nitric oxide production in mouse macrophages when assayed at the 1 μM level.
Abstract: New derivatives of 3-oxoolean-1-en-28-oic acid and 3-oxours-1-en-28-oic acid were synthesized. Nine of them showed significant inhibitory activity against interferon-γ-induced nitric oxide production in mouse macrophages when assayed at the 1 μM level. 3,12-Dioxoolean-1,9-dien-28-oic acid ( 3 ) had the highest activity (IC 50 , 0.9 μM).
TL;DR: In this article, the first photo of an enone and a benzene ring was taken and shown to have high stereoselectivity with a high pressure mercury lamp in the presence of benzil in benzene.
Abstract: N-Benzoyl-N-benzylcinnamamides 1,
N-acetyl-N-(1-benzyl)cinnamamides 3 and
N-[(1-benzyl)aminocarbonyl]-N-(1-benzyl)cinnamamides
5 have been irradiated by a high-pressure mercury lamp in the presence
of benzil in benzene at room temperature to give
3-azatricyclo[5.2.2.01,5]undeca-8,10-dien-4-ones 2, 4 and 6
with high stereoselectivity. These are the first photo[4+2]cycloadducts
of an enone and a benzene ring.
TL;DR: In this article, the carvacrole complex is characterized by single-crystal X-ray analysis, which allowed for the determination of the absolute configuration of the latter, thus, central chirality of carvone has been fully transformed into planar chircality of the carvicrole complex.
TL;DR: The synthesis of tricholomenyn A is described via a route employing two palladium-catalysed Sonogashira coupling reactions, and an efficient, stereoselective route to epitricholomeny A is reported.
Abstract: The synthesis of tricholomenyn A is described
via a route employing two palladium-catalysed
Sonogashira coupling reactions; an efficient, stereoselective route to
epitricholomenyn A is also reported.
TL;DR: Bromonitrile-Noxide adds to the enone completely regio-and stereoselectively to form the bromoisoxazoline 10b/c. The latter can be transformed into the nitrile 11, previously hydrolyzed 14 to the target 16α-carbomethoxyprednisolone 4a a potentially locally active antiinflammatory steroid.
TL;DR: The phosphinoalkynes Ph2PC⋮CR (R = H, Me, CF3, But, Ph, and PPh2) behave as tertiary phosphines in their reactions with the dirhodium complex.
TL;DR: In this article, the development of a new synthetic approach to (−)-Ambrox® (37) and epi-Ambrox (29) using thujone (1) as a chiral synthon is presented.
Abstract: The development of a new synthetic approach to (−)-Ambrox® (37) and epi-Ambrox® (29) using thujone (1) as a chiral synthon, is presented. Thujone (1), a readily available starting material obtained from Western red cedar, can be efficiently converted to β-cyperone (2) and the latter is then chemically elaborated to the key intermediate, the enone 6. A carbonyl transposition of 6 to enone 9 also allows a formal synthesis of (−)-Polywood® (18). Keywords: thujone, β-cyperone, (−)-Ambrox®, epi-Ambrox®, synthesis.
TL;DR: In this paper, the synthesis and mesomorphic properties of several dozen 3,6-disubstituted cyclohex-2-enones are described and the influence of the structure of the reactants, catalysts and solvents on the yield is discussed.
Abstract: The synthesis and mesomorphic properties of several dozen 3,6-disubstituted cyclohex-2-enones are described. The compounds were obtained by the condensation of 4-substituted β-(N,N-dimethylamino)ethylphenyl ketone hydrochlorides (Mannich salts) with 2-alkylacetoacetic esters. The influence of the structure of the reactants, catalysts and solvents on the yield is discussed.
TL;DR: In this article, a one-pot synthesis of bicyclic ethers starting from α,β-unsaturated ketones containing an additional isolated olefinic bond is proposed, which relies on highly chemoselective hydrogenation of the enone group to the corresponding alcohol in the presence of supported copper catalysts.
TL;DR: In this paper, the enantiomerically pure 4-silyloxy enone 6 is prepared in high yields via diastereomeric acetals and equilibration.
TL;DR: The first [3+2] cycloaddition reaction gave the BC ring intermediate, which was then converted into a bicyclic vinylsulfide in three steps as discussed by the authors.
TL;DR: In this article, a new approach to prepare the liquid crystalline bicyclohexylbenzene derivatives is proposed, where the key stage is the synthesis of 3-(trans-4-arylcyclohexynyl)-6-alkyl (or aryl) cyclohex-2-en-1-ones via the condensation of the corresponding Mannich salts with 2-substituted acetoacetic esters (or methyl benzyl ketones) in the presence of a base.
Abstract: A new improved approach to prepare the liquid crystalline bicyclohexylbenzene derivatives is proposed. The key stage is the synthesis of 3-(trans-4-arylcyclohexyl)-6-alkyl (or aryl) cyclohex-2-en-1-ones via the condensation of the corresponding Mannich salts with 2-substituted acetoacetic esters (or methyl benzyl ketones) in the presence of a base. The catalytic hydrogenation of these cyclohexenones in base media gives mainly saturated trans-ketones which are promising semiproducts for the preparation of different kinds of the LC compounds containing a bicyclohexyl fragment. The chemical transformations of the prepared cyclohexanones were carried out and as a result a range of LC compounds both known and new ones were synthesized.
TL;DR: In this paper, an 8-membered ring enone 3 was synthesized from the linear optically active polyoxy-compound 4 by SmI2-mediated intramolecular aldol cyclization.
Abstract: Optically active 2α,10β-dibenzyloxy-11β-(t-butyldimethylsiloxy)-7β-hydroxy-1α-(4-methoxybenzyloxy)–8β,15,15-trimethyl-4-methylene-trans-bicyclo[6.4.0]dodecan-9-one 2 that corresponds to BC ring system of Taxol was prepared from 8-membered ring enone 3 in high yield via stereoselctive Michael addition and successive intramolecular aldol cyclization. The above 8-membered ring enone 3 was synthesized from the linear optically active polyoxy-compound 4 by SmI2-mediated intramolecular aldol cyclization.
TL;DR: In this paper, the tricyclic enone was formed by radical-mediated macrocyclization, followed by transannular Diels-Alder reaction, and the analogous system 13 gave rise to the novel tetracyclic diene-dione 18 presumably by way of the intermediates 14, 16 and 17.
TL;DR: In this article, the synthesis of azadiradione was achieved in nine steps starting from a hydroxy ester using Nazarov cyclization 6→10 and a stereoselective epoxy ketone rearrangement.
TL;DR: In this paper, a condensation of crotononitrile was used to synthesize 5-(N, N-dimethylamino)-2, 4-pentadienenitrile (tertaminodienylnitrile 37).
Abstract: Methyl 5-(N, N-dimethylamino)-2, 4-pentadienoate (tert-aminodienylester 1) was synthesized by condensation of methyl crotonate (2) with N, N, N', N'-tetramethylmethylenediamine (3). The reactivity of 1 was investigated with methyl propiolate (4), dimethyl 2-butynedionate (5), dimethyl maleae (6), dimethyl fumarate (7), 2-buten-4-olide (8), 2-cyclohexenone (9), styrene (10), trans-β-nitrostyrene (11), 1, 4-benzoquinone (19), methyl 1, 4-naphtoquinone-5-carboxylate (21), 1, 4-naphthoquinone (24), juglone (26), 5-methoxy-1, 4-naphthoquinone (28), naphthazarin (31), and naphthazarin dimethyl ether (33). In addition, 5-(N, N-dimethylamino)-2, 4-pentadienenitrile (tert-aminodienylnitrile 37) was synthesized by condensation of crotononitrile (36) with 3. The reactivity of 37 was investigated with dimethyl 2-butynedionate (5), and 2-cyclohexenone (9).
TL;DR: In this article, the total synthesis of (±)-cedranediol (7 ) was achieved using intramolecular double Michael reaction using intrapolynomial double-Michael reaction.