RESUMO
The stereo-controlled total synthesis of (-)-domoic acid is described. The critical construction of the C1'-C2' Z-configuration was accomplished by taking advantage of an unsaturated lactam structure. The side chain fragment was introduced in the final stages of synthesis through a modified Julia-Kocienski reaction, aiming for its efficient derivatization.
Assuntos
Proliferação Nociva de Algas , Receptores Ionotrópicos de Glutamato , Ácido CaínicoRESUMO
One-pot sequential reactions using the acyl moieties installed by enzymatic dynamic kinetic resolution of alcohols have been little investigated. In this work, the acryloyl moiety installed via the lipase/oxovanadium combo-catalyzed dynamic kinetic resolution of a racemic dienol [4-(cyclohex-1-en-1-yl)but-3-en-2-ol or 1-(cyclohex-1-en-1-yl)but-2-en-1-ol] with a (Z)-3-(phenylsulfonyl)acrylate underwent an intramolecular Diels-Alder reaction in a one-pot procedure to produce an optically active naphtho[2,3-c]furan-1(3H)-one derivative (98% ee). This method was successfully applied to the asymmetric total synthesis of (-)-himbacine.
Assuntos
Alcaloides/biossíntese , Furanos/metabolismo , Lipase/metabolismo , Naftalenos/metabolismo , Alcaloides/química , Biocatálise , Reação de Cicloadição , Furanos/química , Cinética , Estrutura Molecular , Naftalenos/química , Piperidinas/química , EstereoisomerismoRESUMO
Total syntheses of teadenols A and B, isolated from fermented tea, were accomplished in a highly stereocontrolled manner. Key steps were an organocatalytic asymmetric α-aminoxylation reaction of an aldehyde and a palladium-catalyzed intramolecular allylic substitution with phenol. In the latter reaction, we utilized the different conformational preferences of cyclic and acyclic carbonate precursors to obtain cis- and trans-fused benzopyran rings, respectively, via intramolecular etherification.
Assuntos
Benzopiranos/química , Fenóis/química , Fenóis/síntese química , Catálise , Técnicas de Química Sintética , Paládio/química , EstereoisomerismoRESUMO
Polyamines, such as spermine (1), thermospermine (2) and norspermine (3), are widely distributed in nature, and have multiple biological activities. In addition, many of their conjugates have potential for pharmacological use. Here, we present a solid-phase synthesis using our nitrobenzenesulfonyl (Ns) strategy, which can provide 1, 2 and 3 on a gram scale. This approach should be suitable for facile construction of a diverse library of polyamines.
Assuntos
Espermina/análogos & derivados , Espermina/síntese química , Estrutura Molecular , Espermina/químicaRESUMO
Both enantiomers of dihydro-ß-ionol and ß-ionol, contained in the aromatic components of Osmanthus flower and of Hakuto peach, were obtained with high optical purity by lipase-catalyzed kinetic resolution of the racemates. It was found that all these enantiomers had different characteristic favorable scents and high antimelanogenetic effects. The absolute configuration and the enantiomer ratios of dihydro-ß-ionol in the aromatic components of Osmanthus flower and of Hakuto peach were determined. The asymmetric synthesis of (R)-dihydro-ß-ionol, one of the most valuable raw materials for fragrance and flavor, was performed from inexpensive ß-ionone via lipase-catalyzed dynamic kinetic resolution followed by reduction.
Assuntos
Fatores Biológicos/química , Norisoprenoides/química , Perfumes/química , Catálise , Flores/química , Cinética , Lipase/química , Prunus/químicaRESUMO
The combination of H(3)[PW(12)O(40)]·nH(2)O (1 mol %) and Et(3)SiH led to the direct catalytic deoxygenation of propargyl alcohols, in which proper solvent selection Cl(CH(2))(2)Cl vs CF(3)CH(2)OH was the key to obtaining better product yields. Under similar conditions, the deoxygenation of allyl alcohols proceeded to give thermodynamically stable alkenes with migration of the double bonds in good yields.
Assuntos
Alcenos/química , Alcinos/química , Ácido Fosfotúngstico/química , Propanóis/química , Catálise , Oxigênio/química , Solventes , TermodinâmicaRESUMO
The combination of (p-CF(3)C(6)H(4))(3)PAuCl and AgOTf generates a powerful catalyst for the intramolecular cyclizations of readily available gamma-hydroxyalkynones under mild conditions. The substituted 3(2H)-furanones are obtained in 55-94% yields. This method is also applicable to the preparation of 2,3-dihydro-4H-pyran-4-ones.
Assuntos
4-Butirolactona/química , Alcanos/química , Ouro/química , Catálise , Cátions , Ciclização , Hidroxilação , Espectroscopia de Ressonância Magnética , Estrutura MolecularRESUMO
Sophoraflavanone H (1) is a polyphenol with a hybrid-type structure containing 2,3-diaryl-2,3-dihydrobenzofuran and flavanone ring moieties. This compound and related analogues are promising leads for antimicrobial and antitumor drug development. Here we describe a total synthesis of 1 and its diastereomer. The dihydrobenzofuran and flavanone rings were constructed by a Rh-catalyzed asymmetric C-H insertion reaction and selective oxy-Michael reaction. The absolute configuration of 1 was established by X-ray crystallographic analysis and CD spectral investigation of synthetic derivatives.
RESUMO
The combination of Mo and cationic Au catalysts dramatically accelerated the rearrangement of diverse propargyl alcohols, which includes a short reaction time, mild conditions, and high product yields. A practical application to the highly challenging primary propargyl alcohols and the N-alkynyl amides is achieved.
Assuntos
Alcinos/química , Ouro/química , Molibdênio/química , Propanóis/química , CatáliseRESUMO
The cyclopentane core framework 23 of pactamycin (1) was synthesized in 14 steps from symmetric cyclohexadiene 11. Our synthetic strategy features Rh-mediated catalytic desymmetrization of 10 via aziridination and then regioselective ring-opening reaction of sulfonylaziridine 9 with NaN3, ring-contraction of cyclohexene 14 by ozonolysis followed by intramolecular aldol reaction, and stereoselective construction of the sequential tetrasubstituted carbons by dihydroxylation and methylation reaction. Stereospecific incorporation of amine on tetrasubstituted carbon was achieved by Curtius rearrangement and subsequent carbamide formation.
RESUMO
An efficient total synthesis of TAN1251C was accomplished by employing a Ugi four-component accumulation reaction and a Dieckmann condensation to construct the spiro-fused cyclohexanone and γ-lactam ring. Diastereoselective reduction by side-chain-controlled hydrogenation of enamide 15 or Zn reduction of oxime 23 enabled construction of the amino group with the desired stereochemistry.
RESUMO
An asymmetric synthesis of highly substituted indenes 3, bearing a quaternary stereogenic carbon center, has been developed via the central-axial-central chirality transfer from optically active propargyl alcohols 1. This transformation involves the addition/rearrangement of 1 and ynamides 2 to give tetra-substituted allenes 4 and further cyclization of 4.
Assuntos
Alcinos/química , Indenos/síntese química , Propanóis/química , Ciclização , Indenos/química , EstereoisomerismoRESUMO
[reaction: see text] Heteroaromatic thioethers and aryl, heteroaryl, and alkenylstannanes participate in a palladium-catalyzed, copper(I)-mediated cross-coupling reaction at 50 degrees C in THF.
Assuntos
Compostos Heterocíclicos/síntese química , Compostos Orgânicos de Estanho/síntese química , Catálise , Cobre/química , Indicadores e Reagentes , Paládio/químicaRESUMO
[reaction: see text] A versatile approach to ketone synthesis is described. The reaction relies on the palladium-catalyzed, copper diphenylphosphinate-mediated coupling of thiol esters with organostannanes under neutral reaction conditions. This reaction complements the previously described coupling of thiol esters with boronic acids that used dual thiophilic-borophilic activation methodology.
Assuntos
Compostos de Bifenilo/química , Cobre/química , Ésteres/química , Cetonas/síntese química , Organofosfonatos/química , Compostos Orgânicos de Estanho/química , Compostos Organometálicos/química , Paládio/química , Compostos de Sulfidrila/químicaRESUMO
AgOTf-catalyzed intramolecular cyclization of phenoxyethynyl diols proceeded under mild conditions to afford the multisubstituted α,ß-unsaturated-γ-lactones in 55-98% yields. This method was also applicable to the synthesis of α,ß-unsaturated-δ-lactones. A similar cyclization proceeded when AgOTf was replaced with a stoichiometric amount of N-bromosuccinimide to furnish the α-bromo-substituted α,ß-unsaturated lactones.