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1.
Biosci Biotechnol Biochem ; 84(1): 178-186, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31581931

RESUMO

Prohydrojasmon has been reported to improve the quality of crops. However, most previous studies have investigated its application on fruits. Here, we evaluated the effect of prohydrojasmon on the growth and total phenolic content, anthocyanin content, and antioxidant activity in komatsuna (Brassica rapa var. periviridis) and lettuce (Lactuca sativa L.). Prohydrojasmon did not show any serious inhibitory effect. Prohydrojasmon applied to komatsuna at a concentration of 0.5 µM significantly increased the total phenolic content and anthocyanin content, and a concentration of 1 µM increased the antioxidant activity. In lettuce, prohydrojasmon at a concentration of 400 µM significantly increased the total phenolic content and anthocyanin content, while a concentration of 0.5 µM significantly increased the antioxidant activity. These results suggest that prohydrojasmon positively affects the phenolic compound and anthocyanin accumulation and antioxidant activity in komatsuna and lettuce without adversely affecting growth.


Assuntos
Antocianinas/metabolismo , Antioxidantes/metabolismo , Brassica rapa/efeitos dos fármacos , Ciclopentanos/farmacologia , Alface/efeitos dos fármacos , Oxilipinas/farmacologia , Reguladores de Crescimento de Planta/farmacologia , Polifenóis/metabolismo , Brassica rapa/crescimento & desenvolvimento , Ciclopentanos/síntese química , Alface/crescimento & desenvolvimento , Oxilipinas/síntese química , Compostos Fitoquímicos/síntese química , Compostos Fitoquímicos/farmacologia , Reguladores de Crescimento de Planta/síntese química , Polifenóis/farmacologia , Transdução de Sinais/efeitos dos fármacos , Verduras/efeitos dos fármacos
2.
Anticancer Res ; 39(8): 4479-4483, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31366548

RESUMO

BACKGROUND/AIM: The stereo-configuration (R-, S-configuration) of chiral-2-nitroimidazole derivatives alters their radiosensitizing activity. This study aimed at examining the molecular features of these enantiomers by molecular simulation techniques. MATERIALS AND METHODS: A series of 2-nitroimidazole-based radiosensitizer TX-2036 molecules were synthesized, and their profiles were examined using molecular structural analysis such as conformation analysis, molecular orbital analysis, and electrostatic potential analysis. RESULTS: R-configured TXs (TX-2043, -2030, -2036) had a weaker radiosensitizing activity than S-configured TXs (TX-2044, -2031, -2037), and R-compounds had a small minus electrostatic potential (ESP) field in the cyclopentene-1,3-dione region. S-configured TX-2046 had weaker radiosensitizing activity than R-configured TX-2045, and TX-2046 had a small minus ESP field as well as R-configured TX-2043, -2030, - 2036. CONCLUSION: The cyclopentene-1,3-dione involved in the small minus ESP field affected the radiosensitizing activity of the TX-2036 series of molecules.


Assuntos
Desenho de Drogas , Nitroimidazóis/química , Tolerância a Radiação/efeitos dos fármacos , Radiossensibilizantes/química , Hipóxia Celular/efeitos dos fármacos , Ciclopentanos/síntese química , Ciclopentanos/química , Humanos , Nitroimidazóis/síntese química , Radiossensibilizantes/síntese química , Eletricidade Estática , Estereoisomerismo , Relação Estrutura-Atividade
3.
Org Biomol Chem ; 17(24): 5951-5961, 2019 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-31166343

RESUMO

The syntheses of conduramine B-2, ent-conduramine F-2, aminocyclopentitol and trihydroxyazepane were accomplished from a common precursor, through a divergent approach using ring closing metathesis (RCM) as the key step. Tri-O-benzyl-d-glucal was converted to 3,4,6-tri-O-benzyl-1,2-dideoxy-2-iodo-1-p-toluenesulfonamido-α-d-mannose. Exposure to NaBH4 in MeOH resulted in a facile 1,2-transposition of the -NHTs group with concomitant glycosylation to give methyl 3,4,6-tri-O-benzyl-2-deoxy-2-p-toluenesulfonamido-ß-d-glucoside, which was converted into methyl 6-deoxy-6-iodo-glucoside in three steps. Zinc-mediated Vasella's rearrangement proceeded smoothly to give the pluripotent formyl-olefin, possessing both electrophilic and nucleophilic sites, which was used as a common precursor in our diversity-oriented approach. Vinylation of the carbonyl group followed by RCM and subsequent deprotection resulted in the successful synthesis of conduramine B-2 and ent-conduramine F-2 for the first time. On the other hand, the Wittig reaction of the formyl-olefin affords the diene that undergoes Grubbs' I catalyzed RCM and deprotection/reduction to provide 3-amino-cyclopentan-1,2-diol. Utilizing the nucleophilic site at the nitrogen of the common precursor, base mediated N-allylation was carried out to obtain the corresponding diene that underwent a smooth RCM to afford trihydroxyazepane.


Assuntos
Azepinas/síntese química , Cicloexilaminas/síntese química , Ciclopentanos/síntese química , Azepinas/química , Cicloexilaminas/química , Ciclopentanos/química , Glicosilação , Estrutura Molecular
4.
Org Lett ; 21(10): 3813-3816, 2019 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-31021646

RESUMO

The Pd-catalyzed coupling of malonate nucleophiles with alkenes bearing tethered aryl or alkenyl triflates is described. These alkene difunctionalization reactions afford malonate-substituted cyclopentanes that contain fused aryl or cycloalkenyl rings. The transformations generate a five-membered ring, two C-C bonds, and provide products bearing up to three stereocenters with good chemical yield and generally high diastereoselectivity.


Assuntos
Alcenos/química , Ciclopentanos/síntese química , Paládio/química , Alquilação , Aminação , Catálise , Ciclopentanos/química , Malonatos , Estrutura Molecular
5.
Org Lett ; 21(2): 567-570, 2019 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-30614709

RESUMO

A complementary process to the Pauson-Khand annulation is described that is well suited to forging densely substituted/oxygenated cyclopentenone products (including fully substituted variants). The reaction is thought to proceed through a sequence of metallacycle-mediated bond-forming events that engages an internal alkyne and a ß-keto ester in an annulation process that forges two C-C bonds. A variant of this annulation process has also been established that delivers deoxygenated cyclopentenones that lack the allylic tertiary alcohol.


Assuntos
Alquinos/química , Ciclopentanos/síntese química , Oxigênio/química , Propanóis/química , Ciclopentanos/química , Estrutura Molecular
6.
Org Biomol Chem ; 16(48): 9461-9471, 2018 12 12.
Artigo em Inglês | MEDLINE | ID: mdl-30516790

RESUMO

A bisphosphine-catalyzed sequential [3 + 2] cycloaddition and Michael addition reaction of ynones with benzylidenepyrazolones has been developed. Under the catalysis of DPPB [1,4-bis(diphenylphosphino)butane], the reaction proceeded smoothly to give spiro-[cyclopentanone] pyrazolone derivatives in moderate to good yields with good diastereoselectivities via sequential dual α',α'-C(sp3)-H bifunctionalization annulation. This strategy provides a novel route toward the synthesis of spiro-[cyclopentanone] pyrazolones containing three contiguous stereocenters which possess potential pharmaceutical activities.


Assuntos
Ciclopentanos/síntese química , Pirazolonas/síntese química , Compostos de Espiro/síntese química , Catálise , Cristalografia por Raios X , Reação de Cicloadição/métodos , Ciclopentanos/química , Modelos Moleculares , Fosfinas/síntese química , Fosfinas/química , Pirazolonas/química , Compostos de Espiro/química , Estereoisomerismo
7.
Org Lett ; 20(23): 7637-7640, 2018 12 07.
Artigo em Inglês | MEDLINE | ID: mdl-30460846

RESUMO

An efficient synthesis of Fmoc-protected ( S, S)- trans-cyclopentane PNA ( tcypPNA) monomers starting from mono-Boc-protected ( S, S)-1,2-cyclopentanediamine is reported. A general synthetic strategy was developed so that tcypPNA monomers with each nucleobase can be made in sufficient quantity and purity for use in solid-phase peptide synthesis (SPPS). The newly synthesized monomers were then successfully incorporated into 10-residue PNA oligomers using standard Fmoc chemistry for SPPS. The different tcypPNAs allow different positions in the sequence to be conformationally constrained with ( S, S)- trans-cyclopentane to determine the effects on binding to complementary DNA.


Assuntos
Ciclopentanos/síntese química , Diaminas/síntese química , Ácidos Nucleicos Peptídicos/síntese química , Ciclopentanos/química , Diaminas/química , Conformação Molecular , Ácidos Nucleicos Peptídicos/química
8.
Molecules ; 23(10)2018 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-30347768

RESUMO

Cationic cyclopentadienyliron (CpFe⁺) is one of the most fruitful organometallic moieties that has been utilized to mediate the facile synthesis of a massive number of macromolecules. However, the ability of this compound to function as a nucleating agent to improve other macromolecule properties has not been explored. This report scrutinizes the influence of the cationic complex as a novel nucleating agent on the spherulitic morphology, crystal structure, and isothermal and non-isothermal crystallization behavior of the Poly(3-hydroxybutyrate) (PHB) bacterial origin. The incorporation of the CpFe⁺ into the PHB materials caused a significant increase in its spherulitic numbers with a remarkable reduction in the spherulitic sizes. Unlike other nucleating agents, the SEM imageries exhibited a good dispersion without forming agglomerates of the CpFe⁺ moieties in the PHB matrix. Moreover, according to the FTIR analysis, the cationic organoiron complex has a strong interaction with the PHB polymeric chains via the coordination with its ester carbonyl. Yet, the XRD results revealed that this incorporation had no significant effect on the PHB crystalline structure. Though the CpFe⁺ had no effect on the polymer's crystal structure, it accelerated outstandingly the melt crystallization of the PHB. Meanwhile, the crystallization half-times (t0.5) of the PHB decreased dramatically with the addition of the CpFe⁺. The isothermal and non-isothermal crystallization processes were successfully described using the Avrami model and a modified Avrami model, as well as a combination of the Avrami and Ozawa methods. Finally, the effective activation energy of the PHB/CpFe⁺ nanocomposites was much lower than those of their pure counterparts, which supported the heterogeneous nucleation mechanism with the organometallic moieties, indicating that the CpFe⁺ is a superior nucleating agent for this class of polymer.


Assuntos
Plásticos Biodegradáveis/química , Ciclopentanos/química , Hidroxibutiratos/química , Compostos Organometálicos/química , Poliésteres/química , Plásticos Biodegradáveis/síntese química , Varredura Diferencial de Calorimetria , Cátions/química , Cristalização , Ciclopentanos/síntese química , Hidroxibutiratos/síntese química , Nanocompostos/química , Compostos Organometálicos/síntese química , Poliésteres/síntese química , Polímeros/síntese química , Polímeros/química , Temperatura Ambiente
9.
J Am Chem Soc ; 140(40): 12710-12714, 2018 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-30216053

RESUMO

Cyclic structures are highly represented in organic molecules, motivating a wealth of catalytic methods targeting their synthesis. Among the various ring-forming processes, cyclooligomerization reactions possess several attractive features but require addressing a unique challenge associated with controlling ring-size selectivity. Here we describe the catalytic reductive cocyclooligomerization of an enone and three carbene equivalents to generate a cyclopentane, a process that constitutes a formal [2 + 1 + 1 + 1]-cycloaddition. The reaction is promoted by a (quinox)Ni catalyst and uses CH2Cl2/Zn as the C1 component. Mechanistic studies are consistent with a metallacycle-based pathway, featuring sequential migratory insertions of multiple carbene equivalents to yield cycloalkanes larger than cyclopropanes.


Assuntos
Reação de Cicloadição/métodos , Ciclopentanos/síntese química , Catálise , Ciclização , Ciclopentanos/química , Metano/análogos & derivados , Metano/síntese química , Metano/química , Modelos Moleculares , Níquel/química , Oxirredução
10.
Molecules ; 23(9)2018 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-30223586

RESUMO

Jasmonates show great potential in sustainable agriculture due to their various roles in natural mechanisms of plant defense, and because they are non-toxic, non-mutagenic, and easily metabolized. The aim of the study was to explore structure⁻activity relationships of dihydrojasmone, cis-jasmone, and their derivatives at the plant⁻aphid interface. We focused on the behavioral responses of aphids, following the exogenous application of natural jasmonates and their derivatives to the host plants. Aphid probing behavior was examined using an electrical penetration graph technique (EPG). The chemoenzymatic transformation of cis-jasmone and the activity of two new derivatives are described. The application of cis-jasmone, dihydrojasmone, the hydroxyderivatives, epoxyderivatives, and alkyl-substituted δ-lactones hindered the foraging activity of Myzus persicae (Sulz.) (Hemiptera: Aphididae) during early stages of probing at the level of non-phloem tissues. The application of saturated bicyclic epoxy-δ-lactone enhanced plant acceptance by M. persicae. Jasmonate derivatives containing a hydroxy group, especially in correlation with a lactone ring, were more active than natural compounds and other derivatives studied. Jasmonates of the present study are worth considering as elements of sustainable aphid control as components of the "push⁻pull" strategy.


Assuntos
Afídeos/fisiologia , Ciclopentanos/síntese química , Oxilipinas/química , Solanum tuberosum/crescimento & desenvolvimento , Animais , Afídeos/efeitos dos fármacos , Comportamento Animal/efeitos dos fármacos , Ciclopentanos/química , Ciclopentanos/farmacologia , Controle de Insetos , Estrutura Molecular , Solanum tuberosum/química , Solanum tuberosum/parasitologia , Relação Estrutura-Atividade
11.
Molecules ; 23(8)2018 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-30060584

RESUMO

The development of novel synthetic routes to produce bioactive compounds starting from renewable sources has become an important research area in organic and medicinal chemistry. Here, we present a low-cost procedure for the tunable and selective conversion of biomass-produced furfural to cyclopentenone derivatives using a mixture of choline chloride and urea as a biorenewable deep eutectic solvent (DES). The proposed medium is a nontoxic, biodegradable, and could be reused up to four times without any unfavorable effect on the reaction yield. The process is tunable, clean, cheap, simple and scalable and meets most of the criteria; therefore, it can be considered as an environmental sustainable process in a natural reaction medium.


Assuntos
Colina/química , Ciclopentanos/síntese química , Furaldeído/química , Solventes/química , Ureia/química , Biodegradação Ambiental , Biomassa , Química Farmacêutica/métodos , Química Verde , Humanos , Temperatura Ambiente
12.
Eur J Med Chem ; 155: 406-417, 2018 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-29906687

RESUMO

Based on the potent anticancer activity of 6'-fluorocyclopentenyl-cytosine 2b in phase IIa clinical trials for the treatment of gemcitabine-resistant pancreatic cancer, we carried out a systematic structure-activity relationship study of 6'-fluorocyclopentenyl-pyrimidines 3a-i and -purines 3j-o to discover novel anticancer agents. We also synthesized the phosphoramidate prodrug 3p of adenine derivative 1b to determine if the anticancer activity depended on the inhibition of DNA and/or RNA polymerase in cancer cells and/or on the inhibition of S-adenosylhomocysteine (SAH) hydrolase. All of the synthesized pyrimidine nucleosides exhibited much less potent anticancer activity in vitro than the cytosine derivative 2b, acting as RNA and/or DNA polymerase inhibitor, indicating that they could not be efficiently converted to their triphosphates for anticancer activity. Among all the synthesized purine nucleosides, adenine derivative 1b and N6-methyladenine derivative 3k showed potent anticancer activity, showing equipotent inhibitory activity as the positive control, neplanocin A (1a) or Ara-C. However, the phosphoramidate prodrug 3p showed less anticancer activity than 1b, indicating that it did not act as a RNA and/or DNA polymerase inhibitor like 2b. This result also demonstrates that the anticancer activity of 1b largely depends on the inhibition of histone methyltransferase, resulting from strong inhibition of SAH hydrolase. The deamination of the N6-amino group, the addition of the bulky alkyl group at the N6-amino group, or the introduction of the amino group at the C2 position almost abolished the anticancer activity.


Assuntos
Antineoplásicos/farmacologia , Ciclopentanos/farmacologia , Desenho de Drogas , Hidrocarbonetos Fluorados/farmacologia , Pró-Fármacos/farmacologia , Purinas/farmacologia , Pirimidinas/farmacologia , Antineoplásicos/síntese química , Antineoplásicos/química , Proliferação de Células/efeitos dos fármacos , Ciclopentanos/síntese química , Ciclopentanos/química , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Hidrocarbonetos Fluorados/síntese química , Hidrocarbonetos Fluorados/química , Estrutura Molecular , Pró-Fármacos/síntese química , Pró-Fármacos/química , Purinas/síntese química , Purinas/química , Pirimidinas/síntese química , Pirimidinas/química , Relação Estrutura-Atividade , Células Tumorais Cultivadas
13.
J Invest Dermatol ; 138(12): 2635-2643, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-29908149

RESUMO

Overexpression of hexokinase 2, and its binding to VDAC1 on the outer mitochondrial membrane of cancer cells, is key to their metabolic reprogramming to aerobic glycolysis, which enables them to proliferate. We describe Comp-1, an allosteric small molecule that selectively detaches hexokinase 2 from the mitochondria. Detachment of hexokinase 2 reduces glycolysis and triggers apoptosis in cancer cells, without affecting hexokinase 1-expressing normal cells. The anti-cancer activity of Comp-1 was demonstrated in the UVB-damaged skin model in SKH-1 mice. Topical treatment with Comp-1 led to 70% reduction in lesion number and area. This in vivo efficacy was obtained without local skin reactions or other safety findings. Mechanism-related pharmacodynamic markers, including hexokinase 2 and cleaved caspase 3 levels, are affected by Comp-1 treatment in vivo. Good Laboratory Practice toxicology studies in minipigs for 28 days and 13 weeks established no systemic toxicities and minimal dermal reaction for once-daily application of up to 20% and 15% ointment strengths, respectively. Thus, Comp-1 may address a significant unmet medical need for a non-irritating efficacious topical actinic keratosis treatment.


Assuntos
Acetatos/uso terapêutico , Antineoplásicos/uso terapêutico , Ciclopentanos/uso terapêutico , Ceratose Actínica/tratamento farmacológico , Neoplasias de Células Escamosas/tratamento farmacológico , Oxilipinas/uso terapêutico , Neoplasias Cutâneas/tratamento farmacológico , Pele/patologia , Raios Ultravioleta/efeitos adversos , Acetatos/síntese química , Acetatos/farmacologia , Animais , Antineoplásicos/síntese química , Antineoplásicos/farmacologia , Apoptose , Linhagem Celular , Ciclopentanos/síntese química , Ciclopentanos/farmacologia , Feminino , Glicólise , Hexoquinase/metabolismo , Humanos , Camundongos , Camundongos Mutantes , Mitocôndrias/metabolismo , Modelos Animais , Oxilipinas/síntese química , Oxilipinas/farmacologia , Pele/efeitos dos fármacos , Suínos , Porco Miniatura , Canal de Ânion 1 Dependente de Voltagem/metabolismo , Ensaios Antitumorais Modelo de Xenoenxerto
14.
J Am Chem Soc ; 140(20): 6426-6431, 2018 05 23.
Artigo em Inglês | MEDLINE | ID: mdl-29712423

RESUMO

A new class of bioorthogonal reagents based on the cyclopentadiene scaffold is described. The diene 6,7,8,9-tetrachloro-1,4-dioxospiro[4,4]nona-6,8-diene (a tetrachlorocyclopentadiene ketal, TCK) is ambiphilic and self-orthogonal with remarkable stability. The diene reacts rapidly with a trans-cyclooctene and an endo-bicyclononyne, but slowly with dibenzoazacyclooctyne (DIBAC), allowing for tandem labeling studies with mutually orthogonal azides that react rapidly with DIBAC. TCK analogues are synthesized in three steps from inexpensive, commercially available starting materials.


Assuntos
Ciclopentanos/síntese química , Azidas/química , Técnicas de Química Sintética , Ciclo-Octanos/química , Ciclopentanos/química , Halogenação , Indicadores e Reagentes , Coloração e Rotulagem
15.
J Am Chem Soc ; 140(16): 5347-5351, 2018 04 25.
Artigo em Inglês | MEDLINE | ID: mdl-29652498

RESUMO

Here, we describe that simple ketones can be efficiently employed as electrophiles in Suzuki-Miyaura coupling reactions via catalytic activation of unstrained C-C bonds. A range of common ketones, such as cyclopentanones, acetophenones, acetone and 1-indanones, could be directly coupled with various arylboronates in high site-selectivity, which offers a distinct entry to more functionalized aromatic ketones. Preliminary mechanistic study suggests that the ketone α-C-C bond was cleaved via oxidative addition.


Assuntos
Carbono/química , Hidrocarbonetos Aromáticos/química , Cetonas/química , Acetona/síntese química , Acetona/química , Acetofenonas/síntese química , Acetofenonas/química , Ácidos Borônicos/síntese química , Ácidos Borônicos/química , Catálise , Técnicas de Química Sintética , Ciclopentanos/síntese química , Ciclopentanos/química , Hidrocarbonetos Aromáticos/síntese química , Cetonas/síntese química , Oxirredução
16.
Molecules ; 23(3)2018 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-29558439

RESUMO

From 1,2;3,4-di-O-isopropylidene-d-galactopyranose, a preliminary series of highly functionalized amino(hydroxymethyl)cyclopentanes was easily available. These amine-containing basic carbasugars featuring the d-galacto configuration are potent inhibitors of the GH20 ß-d-hexosaminidases probed and may bear potential as regulators of N-acetyl-d-hexosaminidase activities in vivo.


Assuntos
Ciclopentanos/farmacologia , Inibidores Enzimáticos/farmacologia , beta-N-Acetil-Hexosaminidases/antagonistas & inibidores , Cristalografia por Raios X , Ciclopentanos/síntese química , Ciclopentanos/química , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Conformação Molecular , beta-N-Acetil-Hexosaminidases/metabolismo
17.
Eur J Med Chem ; 150: 616-625, 2018 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-29550734

RESUMO

The synthesis of both 2'-hydroxy-3'-deoxy and 2'-deoxy-3'-hydroxy cyclopentyl nucleoside phosphonates with the natural nucleobases adenine, thymine, cytosine and guanine from a single precursor has been performed. The guanine containing analogues showed antiviral activity. Especially the 3'-deoxy congener 23 was active, displaying an EC50 of 5.35 µM against TK+ VZV strain and an EC50 of 8.83 µM against TK- VZV strain, besides lacking cytotoxicity. However, the application of phosphonodiamidate prodrug strategy did not lead to a boost in antiviral activity.


Assuntos
Antivirais/farmacologia , Ciclopentanos/farmacologia , Vírus de DNA/efeitos dos fármacos , Nucleosídeos/farmacologia , Organofosfonatos/farmacologia , Antivirais/síntese química , Antivirais/química , Ciclopentanos/síntese química , Ciclopentanos/química , Relação Dose-Resposta a Droga , Humanos , Testes de Sensibilidade Microbiana , Estrutura Molecular , Nucleosídeos/síntese química , Nucleosídeos/química , Organofosfonatos/síntese química , Organofosfonatos/química , Relação Estrutura-Atividade
18.
Angew Chem Int Ed Engl ; 57(22): 6605-6609, 2018 05 28.
Artigo em Inglês | MEDLINE | ID: mdl-29570926

RESUMO

Highly functionalized aminocyclopentadienes can be formed through the rearrangement of anions generated from readily prepared 6-silyl-1,2-dihydropyridines by desilylation with fluoride. The scope and generality of the reaction was defined, and diverse transformations were performed on the highly functionalized products. A mechanism and driving force for the rearrangement were identified from experiments and DFT calculations.


Assuntos
Ciclopentanos/síntese química , Di-Hidropiridinas/química , Ânions/química , Ciclopentanos/química , Teoria da Densidade Funcional
19.
J Am Chem Soc ; 140(6): 1998-2001, 2018 02 14.
Artigo em Inglês | MEDLINE | ID: mdl-29400455

RESUMO

The enantioselective desymmetrization of carboxylic acids by chiral Brønsted base catalysis is reported, leading to bridged bicyclic lactones with up to 94% ee. Crystallographic analysis of a substrate-catalyst complex suggests an origin of stereocontrol, reminiscent of functional Brønsted bases in biological settings, and enabled reaction optimization. The products contain an all-carbon quaternary stereocenter and can be derivatized to functionalized cyclopentanes.


Assuntos
Compostos Bicíclicos com Pontes/síntese química , Ácidos Carboxílicos/química , Lactonas/síntese química , Biomimética , Compostos Bicíclicos com Pontes/química , Ácidos Carboxílicos/síntese química , Catálise , Cristalografia por Raios X , Ciclopentanos/síntese química , Ciclopentanos/química , Lactonas/química , Modelos Moleculares , Estereoisomerismo
20.
J Am Chem Soc ; 140(10): 3514-3517, 2018 03 14.
Artigo em Inglês | MEDLINE | ID: mdl-29465998

RESUMO

We report a stereoselective formal [3 + 2] cycloaddition of cyclopropyl ketones and radical-acceptor alkenes to form polysubstituted cyclopentane derivatives. Catalyzed by a chiral Ti(salen) complex, the cycloaddition occurs via a radical redox-relay mechanism and constructs two C-C bonds and two contiguous stereogenic centers with generally excellent diastereo- and enantioselectivity.


Assuntos
Alcenos/química , Reação de Cicloadição , Ciclopentanos/síntese química , Radicais Livres/química , Cetonas/química , Titânio/química , Catálise , Ciclopentanos/química , Estrutura Molecular , Oxirredução , Estereoisomerismo
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