RESUMO
N-Acyl/sulfonyl-α-functionalized 1,2,3,4-tetrahydroisoquinolines (THIQs) are significant structural motifs in organic synthesis and drug discovery. However, the one-pot approach enabling direct difunctionalization of THIQs remains challenging. Herein we report a photomediated one-pot three-component strategy to access N-acyl/sulfonyl-α-functionalized THIQs. This method features the use of oxygen (from air) as the green oxidant, high atom and step economy, and decent structural diversity. The synthetic applicability of the method was further demonstrated via the facile construction of valuable bioactive molecules. Mechanistic studies indicated that oxidation with singlet oxygen and the acceptor-less dehydrogenation were involved in the photoredox process.
RESUMO
A cooperative tertiary amine/palladium-catalyzed sequential reaction process, proceeding via a [4 + 3] cyclization of isatin-derived Morita-Baylis-Hillman Expansion (MBH) carbonates and tert-butyl 2-(hydroxymethyl)allyl carbonates followed by a [1,3]-rearrangement, has been found and developed. A range of structurally diverse spiro[methylene cyclopentane-1,3'-oxindolines] bearing two adjacent ß,γ-acyl quaternary carbon stereocenters, which are difficult to obtain by conventional strategies, were obtained in good yields. Further synthetic utility of this protocol is highlighted by its excellent regio- and stereocontrol as well as the large-scale synthesis and diverse functional transformations of the synthetic compounds. Moreover, the control experiments probably established the plausible mechanism for this sequential [4 + 3] cyclization/[1,3]-rearrangement process.
Assuntos
Carbonatos , Paládio , Ciclização , Estrutura Molecular , Estereoisomerismo , Catálise , AminasRESUMO
A practical and efficient electrochemical intramolecular amino- or oxysulfonylation of internal alkenes equipped with pendant nitrogen or oxygen-centered nucleophiles with sodium sulfinate was developed. Under undivided electrolytic cell conditions, a variety of sulfonylated N-heterocycles and O-heterocycles, such as tetrahydrofurans, tetrahydropyrans, oxepanes, tetrahydropyrroles, piperidines, δ-valerolactones, etc., were efficiently prepared from easily accessible unsaturated alcohols, carboxylic acids, and N-tosyl amines without the need for additional metal or exogenous oxidant. The robust electrochemical transformation features excellent redox economy, high diastereoselectivity, and broad substrate specificity, which provide a general and practical access to sulfone-containing heterocycles and would facilitate the related synthetic and biological studies based on this electrosynthesis.
RESUMO
An inexpensive copper-catalyzed sequential reaction process, proceeding via a nucleophilic attack of amine to Cu-carbene generated in situ from heterocyclic N-tosylhydrazone precursors followed by a 1,2-H shift/oxidative cyclization cascade of N-ylides, has been described, smoothly generating the corresponding structurally various spiro-dihydropyrrolo[1,2-a]quinoxaline derivatives. Furthermore, the significance of this protocol can be also highlighted by its diverse conversions of the synthetic compounds to the potentially bioactive molecules such as the 2-substituted pyrrolo[1,2-a]quinoxalins.
Assuntos
Cobre , Quinoxalinas , Compostos de Anilina , Catálise , Ciclização , Estrutura MolecularRESUMO
To date, the examples of difunctionalization of alkanes to directly incorporate two functional groups are very limited. In this study, we combined photoorgano redox catalysis and P450 biocatalysts to obtain dioxygen-functionalization of α/ß-C-H bonds of arylalkanes in a straightforward manner. The synthesis of enantiomerically chiral acyloins through a one-pot two-step photoredox/P450-catalyzed cascade reaction is described. Two P450 mutants with stereocomplementary bio-oxidation were obtained using mutagenesis technology and were able to asymmetrically hydroxylate ketones to acyloins with excellent ee values, which were further proved to be efficient on a wide range of substrates. Moreover, a photoredox synthesis of ketones in situ was developed by the direct carbonylation of aromatic methyl C-H bonds and subsequently combined with the aerobic P450-biocatalytic enantioselective hydroxylation of intermediate ketones, thus providing a green and sustainable approach towards optically pure acyloins.
Assuntos
Sistema Enzimático do Citocromo P-450 , Oxigênio , Estereoisomerismo , Sistema Enzimático do Citocromo P-450/química , Cetonas/químicaRESUMO
Expanding the enzymatic toolbox for the green synthesis of valuable molecules is still of high interest in synthetic chemistry and the pharmaceutical industry. Chiral thiiranes are valuable sulfur-containing heterocyclic compounds, but relevant methods for their enantioselective synthesis are limited. Herein, we report a biocatalytic thionation strategy for the enantioselective synthesis of thiiranes, which was developed based on the halohydrin dehalogenase (HHDH)-catalyzed enantioselective ring-opening reaction of epoxides with thiocyanate and a subsequent nonenzymatic rearrangement process. A novel HHDH was identified and engineered for enantioselective biocatalytic thionation of various aryl- and alkyl-substituted epoxides on a preparative scale, affording the corresponding thiiranes in up to 43 % isolated yield and 98 % ee. Large-scale synthesis and useful transformations of chiral thiiranes were also performed to demonstrate the utility and scalability of the biocatalytic thionation strategy.
Assuntos
Compostos de Epóxi , Compostos de Epóxi/química , Estereoisomerismo , BiocatáliseRESUMO
An organometal catalytic conversion of 3-aminooxindoles for the diastereo- and enantioselective synthesis of homoallylic aminooxindoles has been described. The asymmetric allylic alkylation of 3-aminooxindoles with allyl carboxylates proceeded smoothly to afford a series of chiral 3-allyl-3-aminooxindoles. This work offers an alternative route to build these scaffolds. The application of this protocol is also highlighted by a significant conversion of products to the potential applicable spiro[indoline-3,2'-pyrrolidin]-2-one derivatives.
RESUMO
A self-sufficient cytochrome P450 monooxygenase from Deinococcus apachensis (P450DA) was identified and successfully overexpressed in Escherichia coli BL21(DE3). P450DA would be a member of the CYP102D subfamily and assigned as CYP102D2 according to the phylogenetic tree and sequence alignment. Purification and characterization of the recombinant P450DA indicated both NADH and NADPH could be used by P450DA as a reducing cofactor. The recombinant E.â coli (P450DA) strain was functionally active, showing excellent enantioselectivity for benzylic hydroxylation of methyl 2-phenylacetate. Further substrate scope studies revealed that P450DA is able to catalyze benzylic hydroxylation of a variety of compounds, affording the corresponding chiral benzylic alcohols in 86-99 %â ee and 130-1020 total turnover numbers.
Assuntos
Proteínas de Bactérias/metabolismo , Álcool Benzílico/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Deinococcus/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/classificação , Proteínas de Bactérias/genética , Álcool Benzílico/química , Biocatálise , Sistema Enzimático do Citocromo P-450/classificação , Sistema Enzimático do Citocromo P-450/genética , Escherichia coli/metabolismo , Hidroxilação , NADP/química , NADP/metabolismo , Filogenia , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Estereoisomerismo , Especificidade por SubstratoRESUMO
A palladium-catalyzed [2 + 2 + 1] domino annulation of 3-iodochromones, α-bromo carbonyl compounds, and tetracyclododecene (TCD) is described. This approach provides a facile, efficient and atom-economical route to a variety of chromone-containing polycyclic compounds bearing fused/bridged-ring systems in good yields (up to 81%) with excellent diastereoselectivities (99 : 1 dr in all cases).
RESUMO
Cortex Dictamni is extensively used as an herbal medicine worldwide, but is believed to induce hepatotoxicity and even causes mortality in many Asian and European countries. As the most abundant furoquinoline alkaloid ingredient of Cortex Dictamni, dictamnine (DIC) can be metabolically activated by CYP3A to an epoxide metabolite, which possesses the potential to induce hepatotoxicity by covalent binding with proteins. As yet, the hepatotoxicity of DIC and the role played by metabolic activation remain unknown. Here, we found that DIC caused acute liver injury in a time- and dose-dependent manner in mice. The hepatic and urinary DIC epoxide intermediates were observed in DIC-treated mice. Ketoconazole, a CYP3A inhibitor, significantly reduced the hepatotoxicity of DIC and inhibited the formation of reactive metabolites of DIC. Moreover, treatment with 2,3-dihydro-DIC, a DIC analog synthesized by selective reduction of the furan moiety, produced no hepatotoxicity in mice, and no reactive metabolite was formed, suggesting a structural necessity of furan moiety in DIC hepatotoxicity. A time course of gradual hepatic glutathione consumption was observed in DIC-treated mice, while depletion of hepatic glutathione by L-buthionine-S,R-sulfoximine enhanced the hepatotoxicity of DIC. Collectively, this study demonstrates that DIC induces acute hepatocellular injury in mice, and that metabolic activation of furan plays a crucial role in DIC-induced hepatotoxicity.
Assuntos
Doença Hepática Induzida por Substâncias e Drogas/etiologia , Sistema Enzimático do Citocromo P-450/metabolismo , Furanos/metabolismo , Fígado/efeitos dos fármacos , Preparações de Plantas/toxicidade , Quinolinas/toxicidade , Ativação Metabólica , Animais , Doença Hepática Induzida por Substâncias e Drogas/metabolismo , Doença Hepática Induzida por Substâncias e Drogas/patologia , Doença Hepática Induzida por Substâncias e Drogas/prevenção & controle , Citocromo P-450 CYP3A , Inibidores do Citocromo P-450 CYP3A/farmacologia , Relação Dose-Resposta a Droga , Glutationa/metabolismo , Cetoconazol/farmacologia , Fígado/metabolismo , Fígado/patologia , Masculino , Camundongos , Estrutura Molecular , Relação Estrutura-Atividade , Fatores de Tempo , ToxicocinéticaRESUMO
Herein is disclosed a selective and facile approach for the construction of CF2H-containing pyrazolo[1,5- c]quinazolines from easily accessible 3-ylideneoxindoles and in situ generated CF2HCHN2. The reaction involving a [3 + 2] cycloaddition/1,3-H shift/rearrangement/dehydrogenation cascade proceeded smoothly at room temperature in the absence of catalyst and additive. Moreover, this metal-free process along with mild conditions is desirable and valuable for the pharmaceutical industry. Importantly, this reaction features a broad substrate scope, good functional group tolerance, and gram-scale synthesis.
RESUMO
A highly regio- and stereoselective [3 + 2] cycloaddition reaction for constructing novel 3,3'-cyclopentenyldispirooxindoles incorporating two adjacent quaternary spirostereocenters is reported. Under the mild conditions, the asymmetric annulation of isatin-derived MBH carbonates with 3-methyleneoxindoles involving a chiral tertiary amine catalyst provides the corresponding dispirooxindole frameworks with an extraordinary level of enantioselective control. Further synthetic utility of this method was demonstrated by the gram-scale experiment and simple transformation of the obtained product. Moreover, a plausible mechanism for this annulation reaction was also proposed on the basis of the control experiments.
RESUMO
A novel and simple spectrophotometric method is developed for the determination of nitrite in water by using the self-coupling diazotization reagent 2-amino-6-chlorobenzoic acid and UV light illumination. The method only involves one reagent and one step, which can be easily applied to the determination of nitrite and tolerates many foreign anions' effects under acidic conditions.
RESUMO
Halohydrin dehalogenases are remarkable enzymes which possess promiscuous catalytic activity and serve as potential biocatalysts for the synthesis of chiral halohydrins, epoxides and ß-substituted alcohols. The enzyme HheC exhibits a highly R enantioselectivity in the processes of dehalogenation of vicinal halohydrins and ring-opening of epoxides, which attracts more attentions in organic synthesis. Recently dozens of novel potential halohydrin dehalogenases have been identified by gene mining, however, most of the characterized enzymes showed low stereoselectivity. In this study, a novel halohydrin dehalogenase of HheA10 from Tsukamurella sp. 1534 has been heterologously expressed, purified and characterized. Substrate spectrum and kinetic resolution studies indicated the HheA10 was a highly S enantioselective enzyme toward several halohydrins, which produced the corresponding epoxides with the ee (enantiomeric excess) and E values up to >99% and >200 respectively. Our results revealed the HheA10 was a promising biocatalyst for the synthesis of enantiopure aromatic halohydrins and epoxides via enzymatic kinetic resolution of racemic halohydrins. What's more important, the HheA10 as the first individual halohydrin dehalogenase with the highly S enantioselectivity provides a complementary enantioselectivity to the HheC.
Assuntos
Actinomycetales/enzimologia , Hidrolases/metabolismo , Actinomycetales/genética , Actinomycetales/metabolismo , Clonagem Molecular , Compostos de Epóxi/metabolismo , Hidrolases/genética , Cinética , Estereoisomerismo , Especificidade por Substrato , TemperaturaRESUMO
An efficient complementary strategy for the construction of spiro[pyrrolidin-3,2'-oxindole] derivatives has been described. With the sequential nucleophilic benzylation and copper-catalyzed intramolecular C(sp2)-N cross-coupling reaction of 3-aminooxindoles with 2-bromobenzyl bromides, a wide range of 2,3'-spirobi[indolin]-2-ones were smoothly obtained in moderate to good yields. A plausible catalytic cycle for this tandem reaction process was proposed based on the control experiments. This study represents a new perspective for the synthesis of structurally diverse spirocyclic oxindoles by employing 3-aminooxindole substrates.
RESUMO
An organocatalytic and highly diastereo- and enantioselective reaction of 3-aminooxindoles with 2-enoylpyridines for the synthesis of chiral spiro[pyrrolidin-3,2'-oxindole] derivatives has been achieved. With the cinchonidine-based thiourea catalyst, the asymmetric Michael/cyclization reaction sequence of 3-aminooxindoles with 2-enoylpyridines followed by the dehydration and deprotection with concentrated hydrochloric acid provided a wide range of chiral 3',4'-dihydrospiro[indoline-3,2'-pyrrol]-2-ones, bearing two adjacent tri- and tetrasubstituted stereocenters, in moderate to good yields with overall excellent stereoselectivities. The synthetic application of this methodology was presented by the scale-up experiment and transformation of product 5a into the spiro-oxindole-based pyrrolidine 6. Furthermore, a plausible transition state for this cascade reaction sequence was also proposed. And this work will provide a new way to access chiral spiro[pyrrolidin-3,2'-oxindole] derivatives.
Assuntos
Indóis/química , Piridinas/química , Pirróis/síntese química , Compostos de Espiro/química , Ciclização , Estrutura Molecular , Oxindóis , Pirróis/química , EstereoisomerismoRESUMO
A cascade biocatalysis system involving asymmetric hydroxylation and diastereoselective oxidation was developed using Rhodococcus equi ZMU-LK19, which gave chiral 2-substituted-1,2,3,4-tetrahydroquinoline-4-ols (2) (up to 57% isolated yield, 99 : 1 dr, and >99% ee) and chiral 2-substituted-2,3-dihydroquinolin-4(1H)-ones (3) (up to 25% isolated yield, and >99% ee) from (±)-2-substituted-tetrahydroquinolines (1). In addition, a possible mechanism for this cascade biocatalysis was tentatively proposed.
Assuntos
Quinolinas/química , Quinolinas/síntese química , Rhodococcus equi/metabolismo , Biocatálise , Técnicas de Química Sintética , Hidroxilação , Oxirredução , EstereoisomerismoRESUMO
An efficient [3 + 2] cycloaddition of 3-ylideneoxindoles with in situ generated CF2HCHN2 for the syntheses of spirooxindoles has been developed. This methodology gives access to a range of relatively complex spirooxindoles featuring a CF2H group and three contiguous stereogenic centers in up to 84% yield and 99 : 1 trans/cis.
RESUMO
A highly efficient asymmetric Mannich reaction of 3-monosubstituted 3-aminooxindoles/3-hydroxyoxindoles with in situ generated N-Boc-protected aldimines catalyzed by the chiral bifunctional thiourea-tertiary amine catalyst has been developed. Under mild reaction conditions, a series of structurally diverse vicinal oxindole-diamines/amino alcohols were smoothly obtained in moderate to high yields (up to 99%) with good to excellent diastereoselectivities and enantioselectivities (up to 95:5 dr and 96% ee). The synthetic application of this protocol was also demonstrated by the versatile transformation of chiral vicinal oxindole-diamine/amino alcohol into spirocyclic oxindoles.
RESUMO
A facile and practical palladium-catalyzed nucleophilic substitution/C-H activation/aromatization cascade reaction has been developed. A range of 6-unsubstituted phenanthridines could be obtained in moderate to good yields (31-85%) with readily prepared N-Ms arylamines and commercially available 2-bromobenzyl bromide derivatives as starting materials. The potential application of the protocol was also demonstrated by the expeditious synthesis of the natural alkaloid trisphaeridine.