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1.
Food Chem ; 336: 127551, 2021 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32795783

RESUMO

The inhibitory effects of Portulaca oleracea L. (PO) and its flavonoid ingredients on the formation of heterocyclic amines (HAs) in roast beef patties were investigated. Ten HAs were found in control patties, and the total content was 212.73 ± 7.13 ng/g. With the addition of PO (1%, 5%, and 10%, w/w), HAs decreased by 62.39%, 68.03%, and 73.75%, respectively. The main flavonoid ingredients (rutin, hesperidin, and flavanone) also present a similar inhibitory effect. The Density Function Theory (DFT) methods were adopted to investigate the inhibitory mechanism. These ingredients bonded with the intermediate to block the formation of norharman. Both experimental and calculated data of the ingredients were analyzed on their HAs inhibitory capacity. Our results provide a novel and valuable strategy to reduce HAs via a low additive level of medicinal and edible plants. And the correlation between experimental and calculated data could be applied to predict the inhibitory ability of inhibitors.


Assuntos
Aminas/química , Flavonoides/química , Portulaca/química , Carne Vermelha/análise , Aminas/análise , Aminas/metabolismo , Animais , Antioxidantes/química , Bovinos , Cromatografia Líquida de Alta Pressão , Teoria da Densidade Funcional , Compostos Heterocíclicos/química , Portulaca/metabolismo , Espectrometria de Massas em Tandem
2.
Yakugaku Zasshi ; 140(10): 1225-1233, 2020.
Artigo em Japonês | MEDLINE | ID: mdl-32999201

RESUMO

This article describes our stereoselective and site-selective chemical methods for exploiting cationic heterocycles as electron-withdrawing groups (EWGs). We envisioned that the phosphoramide N-H proton of a pyridyl phosphoramide 3 would be activated by the cationic pyridinium moiety that is formed upon protonation. The resulting imide-like N-H proton and the acidic pyridinium proton of the pyridinium phosphoramide 3⋅HX cooperate together, making 3⋅HX a highly acidic dual Brønsted acid. The catalytic ability of 3⋅HX was demonstrated in the development of the first asymmetric Diels-Alder reaction between 1-amide dienes and maleimides. Focusing on the activation of N-bromosuccinimide (NBS) because of its structural similarity to maleimides, the enantioselective bromolactonization of trisubstituted olefinic acids was accomplished utilizing pyridyl phosphoramide 3f as a Brønsted base catalyst bearing an acidic N-H proton. Lastly, our strategy for the site-selective acylation of polyol compounds is described. In our system, a pyridine aldoxime ester 10, used as a mild acylating reagent, was activated by a catalytic amount of Lewis acid via the inductive effect of the cationic pyridinium moiety. The resulting metal complex preferentially attracted the alcohol with a Lewis basic site, thereby facilitating selective acylation via a template effect. This metal-template-driven strategy allowed for the site-selective acylation of diverse α-hydroxyamides, including unprotected N-glycolyl aminosugars.


Assuntos
Cátions/química , Cátions/síntese química , Química Orgânica/métodos , Desenvolvimento de Medicamentos/métodos , Elétrons , Compostos Heterocíclicos/química , Compostos Heterocíclicos/síntese química , Acilação , Amidas/química , Catálise , Complexos de Coordenação/química , Reação de Cicloadição , Ésteres/química , Compostos de Pralidoxima/química , Estereoisomerismo
3.
Acta Crystallogr C Struct Chem ; 76(Pt 8): 795-809, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32756043

RESUMO

The crystal structures of four new chiral [1,2,3]triazolo[5,1-b][1,3,4]thiadiazines are described, namely, ethyl 5'-benzoyl-5'H,7'H-spiro[cyclohexane-1,6'-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine]-3'-carboxylate, C19H22N4O3S, ethyl 5'-(4-methoxybenzoyl)-5'H,7'H-spiro[cyclohexane-1,6'-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine]-3'-carboxylate, C20H24N4O4S, ethyl 6,6-dimethyl-5-(4-methylbenzoyl)-6,7-dihydro-5H-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine-3-carboxylate, C17H20N4O3S, and ethyl 5-benzoyl-6-(4-methoxyphenyl)-6,7-dihydro-5H-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine-3-carboxylate, C21H20N4O4S. The crystallographic data and cell activities of these four compounds and of the structures of three previously reported similar compounds, namely, ethyl 5'-(4-methylbenzoyl)-5'H,7'H-spiro[cyclopentane-1,6'-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine]-3'-carboxylate, C19H22N4O3S, ethyl 5'-(4-methoxybenzoyl)-5'H,7'H-spiro[cyclopentane-1,6'-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine]-3'-carboxylate, C19H22N4O4S, and ethyl 6-methyl-5-(4-methylbenzoyl)-6-phenyl-6,7-dihydro-5H-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine-3-carboxylate, C22H22N4O3S, are contrasted and compared. For both crystallization and an MTT assay, racemic mixtures of the corresponding [1,2,3]triazolo[5,1-b][1,3,4]thiadiazines were used. The main manner of molecular packing in these compounds is the organization of either enantiomeric pairs or dimers. In both cases, the formation of two three-centre hydrogen bonds can be detected resulting from intramolecular N-H...O and intermolecular N-H...O or N-H...N interactions. Molecules of different enantiomeric forms can also form chains through N-H...O hydrogen bonds or form layers between which only weak hydrophobic contacts exist. Unlike other [1,2,3]triazolo[5,1-b][1,3,4]thiadiazines, ethyl 5'-benzoyl-5'H,7'H-spiro[cyclohexane-1,6'-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine]-3'-carboxylate contains molecules of only the (R)-enantiomer; moreover, the N-H group does not participate in any significant intermolecular interactions. Molecular mechanics methods (force field OPLS3e) and the DFT B3LYP/6-31G+(d,p) method show that the compound forming enantiomeric pairs via weak N-H...N hydrogen bonds is subject to greater distortion of the geometry under the influence of the intermolecular interactions in the crystal. For intramolecular N-H...O and S...O interactions, an analysis of the noncovalent interactions (NCIs) was carried out. The cellular activities of the compounds were tested by evaluating their antiproliferative effect against two normal human cell lines and two cancer cell lines in terms of half-maximum inhibitory concentration (IC50). Some derivatives have been found to be very effective in inhibiting the growth of Hela cells at nanomolar and submicromolar concentrations with minimal cytotoxicity in relation to normal cells.


Assuntos
Cicloexanos/química , Compostos Heterocíclicos/farmacologia , Tiadiazinas/química , Cristalografia por Raios X , Células HeLa , Compostos Heterocíclicos/química , Humanos , Ligação de Hidrogênio , Conformação Molecular , Estereoisomerismo , Tiadiazinas/farmacologia
4.
J Oleo Sci ; 69(8): 871-882, 2020 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-32641614

RESUMO

In this study, an N-heterocyclic carbene (NHC)-based metal coordinate surfactant (MCS), NHC-Au-MCS, in which the NHC framework afforded the bonding of the Au(I) at the linkage of the hydrophilic and hydrophobic moieties, was synthesized. The structure of NHC-Au-MCS was confirmed by 1H and 13C NMR spectroscopic measurements together with elemental analysis. Matrix-assisted laser desorption/ionization (MALDI), laser desorption/ionization (LDI), and electrospray ionization mass spectrometry (ESI-MS) indicated the distinct reactivity of NHC-Au-MCS, such as the exchange of Br to Cl and the formation of a cationic Au complex, where the two NHC ligands were coordinated to an Au(I) center upon laser activation. The surface tension and dynamic light scattering (DLS) measurements revealed that the coordination of Au(I) to NHC reduced the critical micelle concentration (CMC) of NHC-Au-MCS (1.3×10-5 M), which resulted in the formation of micelles at concentrations higher than the CMC in water. We also confirmed that the surface-active Au(I) complex of NHC-Au-MCS catalyzed the hydration of 1-dodecyne to 2-dodecanone in water in the absence of an organic solvent. On the basis of the detailed mechanistic investigations regarding the reactivity of NHC-Au-MCS, we revealed that NHC-Au-MCS partially translated into Au nanoparticles (AuNPs), which facilitated alkyne hydration. These mechanistic studies were supported by UV-vis measurements, transmission electron microscopy (TEM), and LDI-MS.


Assuntos
Alquinos/química , Ouro/química , Compostos Heterocíclicos/síntese química , Nanopartículas Metálicas/química , Metano/análogos & derivados , Tensoativos/síntese química , Catálise , Compostos Heterocíclicos/química , Hidrogenação , Interações Hidrofóbicas e Hidrofílicas , Metano/síntese química , Metano/química , Micelas , Tensoativos/química , Água
5.
Food Chem ; 331: 127264, 2020 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-32619906

RESUMO

This work aimed to develop a method permitting an informed choice of antioxidants to reduce carcinogenic heterocyclic aromatic amine (HAA) formation during proteinaceous food cooking. Therefore, a three-step approach was developed. First, the most promising antioxidants were selected using molecular modeling approaches. For this, analog design was used to highlight the most suitable antioxidants based on their diversification potential using bioisosteric replacement. Then, structure activity relationship studies allowed drawing the relevant properties for inhibiting HAA formation and explained partly the inhibitory activity. Secondly, the approved antioxidants were tested in ground beef patties to assess their inhibitory properties against HAA formation. Resveratrol was found to be the most efficient as it totally inhibited MeIQ and reduced MeIQx and PhIP formation by 40 and 70%, respectively. Finally, natural ingredients rich in these antioxidants were evaluated. Oregano was found to totally inhibit MeIQ formation and to reduce by half MeIQx and PhIP formation.


Assuntos
Antioxidantes/química , Culinária/métodos , Compostos Heterocíclicos/química , Carne Vermelha , Relação Estrutura-Atividade , Aminas/química , Animais , Bovinos , Modelos Moleculares , Origanum/química , Extratos Vegetais , Quinolinas/química , Quinoxalinas/química , Resveratrol/química , Chá , Vinho
6.
Nat Commun ; 11(1): 2890, 2020 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-32513962

RESUMO

Employment of sulfoxides as electrophiles in cross-coupling reactions remains underexplored. Herein we report a transition-metal-free cross-coupling strategy utilizing aryl(heteroaryl) methyl sulfoxides and alcohols to afford alkyl aryl(heteroaryl) ethers. Two drug molecules were successfully prepared using this protocol as a key step, emphasizing its potential utility in medicinal chemistry. A DFT computational study suggests that the reaction proceeds via initial addition of the alkoxide to the sulfoxide. This adduct facilitates further intramolecular addition of the alkoxide to the aromatic ring wherein charge on the aromatic system is stabilized by the nearby potassium cation. Rate-determining fragmentation then delivers methyl sulfenate and the aryl or heteroaryl ether. This study establishes the feasibility of nucleophilic addition to an appended sulfoxide as a means to form a bond to aryl(heteroaryl) systems and this modality is expected to find use with many other electrophiles and nucleophiles leading to new cross-coupling processes.


Assuntos
Álcoois/química , Éteres/química , Hidrocarbonetos Policíclicos Aromáticos/química , Sulfóxidos/química , Elementos de Transição/química , Carbono/química , Catálise , Química Farmacêutica/métodos , Compostos Heterocíclicos/química , Hidrocarbonetos Aromáticos/química , Metais/química , Modelos Químicos , Estrutura Molecular , Hidrocarbonetos Policíclicos Aromáticos/síntese química , Enxofre/química
7.
Nat Commun ; 11(1): 2740, 2020 06 02.
Artigo em Inglês | MEDLINE | ID: mdl-32488094

RESUMO

Induced fit and conformational selection are two dominant binding mechanisms in biology. Although induced fit has been widely accepted by supramolecular chemists, conformational selection is rarely studied with synthetic systems. In the present research, we report a macrocyclic host whose binding mechanism is unambiguously assigned to conformational selection. The kinetic and thermodynamic aspects of this system are studied in great detail. It reveals that the kinetic equation commonly used for conformational selection is strictly followed here. In addition, two mathematical models are developed to determine the association constants of the same guest to the two host conformations. A "conformational selectivity factor" is defined to quantify the fidelity of conformational selection. Many details about the kinetic and thermodynamic aspects of conformational selection are revealed by this synthetic system. The conclusion and the mathematical models reported here should be helpful in understanding complex molecular recognition in both biological and synthetic systems.


Assuntos
Fenômenos Biofísicos , Domínios Proteicos , Proteínas/metabolismo , Compostos Heterocíclicos/química , Compostos Heterocíclicos/metabolismo , Cinética , Ligantes , Modelos Moleculares , Modelos Teóricos , Ligação Proteica , Conformação Proteica , Proteínas/química , Termodinâmica
8.
PLoS Pathog ; 16(6): e1008485, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32589689

RESUMO

Ozonide antimalarials, OZ277 (arterolane) and OZ439 (artefenomel), are synthetic peroxide-based antimalarials with potent activity against the deadliest malaria parasite, Plasmodium falciparum. Here we used a "multi-omics" workflow, in combination with activity-based protein profiling (ABPP), to demonstrate that peroxide antimalarials initially target the haemoglobin (Hb) digestion pathway to kill malaria parasites. Time-dependent metabolomic profiling of ozonide-treated P. falciparum infected red blood cells revealed a rapid depletion of short Hb-derived peptides followed by subsequent alterations in lipid and nucleotide metabolism, while untargeted peptidomics showed accumulation of longer Hb-derived peptides. Quantitative proteomics and ABPP assays demonstrated that Hb-digesting proteases were increased in abundance and activity following treatment, respectively. Ozonide-induced depletion of short Hb-derived peptides was less extensive in a drug-treated K13-mutant artemisinin resistant parasite line (Cam3.IIR539T) than in the drug-treated isogenic sensitive strain (Cam3.IIrev), further confirming the association between ozonide activity and Hb catabolism. To demonstrate that compromised Hb catabolism may be a primary mechanism involved in ozonide antimalarial activity, we showed that parasites forced to rely solely on Hb digestion for amino acids became hypersensitive to short ozonide exposures. Quantitative proteomics analysis also revealed parasite proteins involved in translation and the ubiquitin-proteasome system were enriched following drug treatment, suggestive of the parasite engaging a stress response to mitigate ozonide-induced damage. Taken together, these data point to a mechanism of action involving initial impairment of Hb catabolism, and indicate that the parasite regulates protein turnover to manage ozonide-induced damage.


Assuntos
Adamantano/análogos & derivados , Antimaláricos/farmacologia , Eritrócitos , Hemoglobinas/metabolismo , Compostos Heterocíclicos com 1 Anel/farmacologia , Peróxidos/farmacologia , Plasmodium falciparum/metabolismo , Compostos de Espiro/farmacologia , Adamantano/farmacologia , Eritrócitos/metabolismo , Eritrócitos/parasitologia , Hemoglobinas/genética , Compostos Heterocíclicos/química , Compostos Heterocíclicos/farmacologia , Humanos , Plasmodium falciparum/genética , Proteômica
9.
J Leukoc Biol ; 107(6): 1123-1135, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32374043

RESUMO

Chemokines play critical roles in numerous physiologic and pathologic processes through their action on seven-transmembrane (TM) receptors. The N-terminal domain of chemokines, which is a key determinant of signaling via its binding within a pocket formed by receptors' TM helices, can be the target of proteolytic processing. An illustrative case of this regulatory mechanism is the natural processing of CXCL12 that generates chemokine variants lacking the first two N-terminal residues. Whereas such truncated variants behave as antagonists of CXCR4, the canonical G protein-coupled receptor of CXCL12, they are agonists of the atypical chemokine receptor 3 (ACKR3/CXCR7), suggesting the implication of different structural determinants in the complexes formed between CXCL12 and its two receptors. Recent analyses have suggested that the CXCL12 N-terminus first engages the TM helices of ACKR3 followed by the receptor N-terminus wrapping around the chemokine core. Here we investigated the first stage of ACKR3-CXCL12 interactions by comparing the activity of substituted or N-terminally truncated variants of CXCL12 toward CXCR4 and ACKR3. We showed that modification of the first two N-terminal residues of the chemokine (K1R or P2G) does not alter the ability of CXCL12 to activate ACKR3. Our results also identified the K1R variant as a G protein-biased agonist of CXCR4. Comparative molecular dynamics simulations of the complexes formed by ACKR3 either with CXCL12 or with the P2G variant identified interactions between the N-terminal 2-4 residues of CXCL12 and a pocket formed by receptor's TM helices 2, 6, and 7 as critical determinants for ACKR3 activation.


Assuntos
Quimiocina CXCL12/química , AMP Cíclico/química , Receptores CXCR4/química , Receptores CXCR/química , Sequência de Aminoácidos , Sítios de Ligação , Quimiocina CXCL11/química , Quimiocina CXCL11/genética , Quimiocina CXCL11/metabolismo , Quimiocina CXCL12/genética , Quimiocina CXCL12/metabolismo , AMP Cíclico/metabolismo , Expressão Gênica , Células HEK293 , Compostos Heterocíclicos/química , Compostos Heterocíclicos/farmacologia , Humanos , Simulação de Dinâmica Molecular , Mutação , Oligopeptídeos/química , Oligopeptídeos/farmacologia , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Receptores CXCR/genética , Receptores CXCR/metabolismo , Receptores CXCR4/antagonistas & inibidores , Receptores CXCR4/genética , Receptores CXCR4/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , beta-Arrestinas/genética , beta-Arrestinas/metabolismo
10.
Top Curr Chem (Cham) ; 378(3): 39, 2020 05 04.
Artigo em Inglês | MEDLINE | ID: mdl-32367181

RESUMO

During the last decade, organometallic, coordination, and catalytic chemistry of the three-dimensional metals such as copper (Cu) has been greatly affected by the emergence of nitrogen heterocyclic carbene (NHC) complexes. The NHCs, and in particular the mononuclear CuI-based ones, have been proven vastly useful in several applications such as in biosynthesis, catalysis, photochemistry, etc. This review tries to thoroughly describe a series of mononuclear CuI NHC complexes and their subcategories such as heteroleptics, and bidentate and tridentate heteroatom complexes, and give some detailed insights on their development, emergence, and applications. A brief outlook is also disclosed to enable other researchers to further develop a platform for future advances and studies in the field of CuI-based NHCs.


Assuntos
Complexos de Coordenação/química , Cobre/química , Compostos Heterocíclicos/química , Metano/análogos & derivados , Nitrogênio/química , Complexos de Coordenação/síntese química , Metano/química , Estrutura Molecular
11.
Food Chem ; 324: 126898, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32361096

RESUMO

Reactions involving reactive carbonyls, creatinine, and ammonia-producing compounds were investigated in order to clarify the formation of the heterocyclic aromatic amine (HAA) 2-amino-3,4-dimethylimidazo(4,5-f)quinoline (MeIQ). Obtained results showed that MeIQ was only produced when 2-butenal (crotonaldehyde) was present. Reaction yields depended on the pH, with a maximum around pH 6.5, and on concentrations of crotonaldehyde and creatinine. Ammonia was also required for MeIQ formation, but ammonia was produced by creatinine decomposition. The amount of MeIQ formed increased with reaction time, temperature, and oxygen content in the reaction atmosphere. Activation energy for MeIQ formation from crotonaldehyde, creatinine, and glutamine was 72.2 ± 0.4 kJ·mol-1. A reaction pathway that explains MeIQ formation is proposed. Obtained results suggest a main role of reactive carbonyls formed in foods (the food carbonylome) on HAA formation. In addition, they provide scientific basis for the understanding of how HAAs are formed and could be mitigated.


Assuntos
Aldeídos/química , Creatinina/química , Quinolinas/química , Amônia/química , Cromatografia Líquida de Alta Pressão , Compostos Heterocíclicos/química , Concentração de Íons de Hidrogênio , Oxigênio/química , Quinolinas/análise , Espectrometria de Massas em Tandem , Temperatura
12.
Food Chem ; 326: 127016, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32428855

RESUMO

The effects of sodium tripolyphosphate (TPP), sodium pyrophosphate (PP), and NaCl at different ionic strengths on the formation of heterocyclic amines (HAs) were investigated in roasted beef patties. Six HAs (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine [PhIP], 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline [MeIQx], 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline [4,8-DiMeIQx], 2-amino-3-methylimidazo[4,5-f]quinoline [IQ], 1-methyl-9H-pyrido[3,4-b] indole [harman], and 9H-pyrido[3,4-b] indole [norharman]) were identified and quantified. The presence of 0.3% and 0.45% PP significantly increased the formation of PhIP (P < 0.05). Different levels of TPP/PP had no effect on MeIQx, 4,8-DiMeIQx, IQ, norharman, or harman (P > 0.05), but these products increased in the presence of NaCl at three ionic strengths and NaCl + 0.3% and 0.45% TPP/PP (P < 0.05). High hardness and surface temperatures were observed after treatments with NaCl and NaCl + TPP/PP. The increase in these six HAs in beef patties with the addition of polyphosphates and NaCl did not involve changes in pH, but mainly stemmed from higher surface temperatures during roasting.


Assuntos
Aminas/química , Compostos Heterocíclicos/química , Carne/análise , Carne Vermelha/análise , Cloreto de Sódio/química , Animais , Bovinos , Cromatografia Líquida de Alta Pressão , Culinária , Temperatura Alta , Espectrometria de Massas em Tandem
13.
Org Biomol Chem ; 18(15): 2793-2812, 2020 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-32239033

RESUMO

The current review summarizes the latest achievements in the synthesis of piperidine-2,4-dione-type azaheterocycles. Two main groups traditional (carbonyl compound transformations) and novel (anionic enolate rearrangements) of complementary methods for the simple and effective preparation of structurally diverse compounds in racemic and enantiopure forms have been reported. Due to the specific structure and appropriate reactivity profiles of dione-type molecules, they are a convenient modern platform for the construction of functionalized piperidine-type systems possessing high synthetic and medicinal potential. This potential is successfully realized by the creation of highly active pharmaceutically relevant compounds and the synthesis of natural products.


Assuntos
Compostos Aza/síntese química , Produtos Biológicos/síntese química , Desenvolvimento de Medicamentos , Compostos Heterocíclicos/síntese química , Piperidonas/síntese química , Compostos Aza/química , Produtos Biológicos/química , Compostos Heterocíclicos/química , Estrutura Molecular , Piperidonas/química
14.
Nat Commun ; 11(1): 1273, 2020 03 09.
Artigo em Inglês | MEDLINE | ID: mdl-32152321

RESUMO

The importance of N-heterocycles in drugs has stimulated diverse methods for their efficient syntheses. Methods that introduce significant stereochemical complexity are attractive for identifying new bioactive amine chemical space. Here, we report a [3 + 3] ring expansion of bicyclic aziridines and rhodium-bound vinyl carbenes to form complex dehydropiperidines in a highly stereocontrolled rearrangement. Mechanistic studies and DFT computations indicate that the reaction proceeds through formation of a vinyl aziridinium ylide; this reactive intermediate undergoes a pseudo-[1,4]-sigmatropic rearrangement to directly furnish heterocyclic products with net retention at the new C-C bond. In combination with asymmetric silver-catalyzed aziridination, enantioenriched scaffolds with up to three contiguous stereocenters are rapidly delivered. The mild reaction conditions, functional group tolerance, and high stereospecificity of this method are well-suited for appending piperidine motifs to natural product and complex molecules. Ultimately, our work establishes the value of underutilized aziridinium ylides as key intermediates for converting small, strained rings to larger N-heterocycles.


Assuntos
Aziridinas/química , Piperidinas/química , Catálise , Compostos Heterocíclicos/química , Estereoisomerismo
15.
Chemistry ; 26(27): 6056-6063, 2020 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-32133687

RESUMO

The properties of LnIII -HPDO3A complexes as relaxation enhancers and paraCEST agents are essentially related to the hydroxylpropyl moiety. A series of three HPDO3A derivatives, with small modifications to the hydroxyl arm, were herein investigated to understand how heightened control can be gained over the parameters involved in the design of these agents. A full 1 H and 17 O-NMR relaxometric analysis was conducted and demonstrated that increasing the length of the OH group from the lanthanide centre significantly enhanced the water exchange rate of the gadolinium complex, but with a subsequent reduction in kinetic stability. Alternatively, the introduction of an additional methyl group, which increased the steric bulk around the OH moiety, resulted in the formation of almost exclusively the TSAP isomer (95 %) as identified by 1 H-NMR of the europium complex. The gadolinium analogue of this complex also exhibited a very fast water exchange rate, but with no detectable loss of kinetic stability. This complex therefore demonstrates a notable improvement over Gd-HPDO3A.


Assuntos
Meios de Contraste/química , Gadolínio/química , Elementos da Série dos Lantanídeos/química , Imagem por Ressonância Magnética/métodos , Európio/química , Compostos Heterocíclicos/química , Cinética , Compostos Organometálicos/química , Água
16.
PLoS One ; 15(3): e0230540, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32182285

RESUMO

Halide vacancies and associated metallic lead (Pb°) observed at the surface and deep inside macroscopic organolead trihalide perovskite crystals is removed through a facile and noninvasive treatment. Indeed, Br2 vapor is shown to passivate Br-vacancies and associated Pb° in the bulk of macroscopic crystals. Controlling the exposure time can markedly improve the overall stoichiometry for moderate exposures or introduce excessive bromide for long exposures, resulting in p-doping of the crystals. In the low dose passivation regime, Hall effect measurements reveal a ca. 3-fold increase in carrier mobility to ca. 15 cm2V-1s-1, while the p-doping increases the electrical conductivity ca. 10000-fold, including a 50-fold increase in carrier mobility to ca. 150 cm2V-1s-1. The ease of diffusion of Br2 vapor into macroscopic crystals is ascribed to the porosity allowed in rapidly grown crystals through aggregative processes of the colloidal sol during growth of films and macroscopic crystals. This process is believed to form significant growth defects, including open voids, which may be remnants of the escaping solvent at the solidification front. These results suggest that due to the sol-gel-like nature of the growth process, macroscopic perovskite crystals reported in this study are far from perfect and point to possible pathways to improving the optoelectronic properties of these materials. Nevertheless, the ability of the vapor-phase approach to access and tune the bulk chemistry and properties of nominally macroscopic perovskite crystals provides interesting new opportunities to precisely manipulate and functionalize the bulk properties of hybrid perovskite crystals in a noninvasive manner.


Assuntos
Compostos de Cálcio/química , Óxidos/química , Titânio/química , Brometos/química , Doping nos Esportes , Compostos Heterocíclicos/química , Humanos
17.
Chemistry ; 26(31): 7083-7091, 2020 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-32073723

RESUMO

The electron donor tetrathiafulvalene (D1 ) was fused onto the electron-rich heterabuckybowl trichalcogenasumanene (D2 ) through an electron-deficient pyrazine unit (A) to give 1 c, 1 d, 2 c, and 2 d, featuring the D1 -A-D2 structure. Both D1 and D2 play a pivotal role in intramolecular charge-transfer (ICT) transitions, consequently 1 c, 2 d, 2 c, and 2 d show a broad ICT band at 450-720 nm in steady state. They exhibit two charge-separated transient states, CS1 and CS2 , that appear in sequence. CS1 has a short lifetime (542 fs), and the D1 moiety on CS1 is in the radical cation state with an absorption maximum (λmax ) at 889 nm. CS1 then converts into CS2 (λmax , 1105 nm) through an ICT between D1 .+ and D2 , affording D1 (1-δ).+ and D2 δ.+ . Compounds 1 c, 1 d, 2 c, and 2 d show protonation-induced intramolecular electron transfer that leads to absorption at λ=700-1300 nm. Owing to the existence of an electron-rich C=C bond on the D1 moiety and in situ generation of 1 O2 by the pyrazine-fused D2 moiety, compounds 1 c, 1 d, 2 c, and 2 d display self-sensitized photooxidation in 50 s.


Assuntos
Compostos Heterocíclicos/química , Pirazinas/química , Transporte de Elétrons , Elétrons , Hidrogenação , Estrutura Molecular
18.
AAPS PharmSciTech ; 21(3): 96, 2020 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-32103355

RESUMO

The true density of an amorphous solid is an important parameter for studying and modeling materials behavior. Experimental measurements of density using helium pycnometry are standard but may be prevented if the material is prone to rapid recrystallization, or preparation of gram quantities of reproducible pure component amorphous materials proves impossible. The density of an amorphous solid can be approximated by assuming it to be 95% of its respective crystallographic density; however, this can be inaccurate or impossible if the crystal structure is unknown. Molecular dynamic simulations were used to predict the density of 20 amorphous solid materials. The calculated density values for 10 amorphous solids were compared with densities that were experimentally determined using helium pycnometry. In these cases, the amorphous densities calculated using molecular dynamics had an average percent error of - 0.7% relative to the measured values, with a maximum error of - 3.48%. In contrast, comparisons of amorphous density approximated from crystallographic structures with pycnometrically measured values resulted in an average percent error of + 3.7%, with a maximum error of + 9.42%. These data suggest that the density of an amorphous solid can be accurately predicted using molecular dynamic simulations and allowed reliable calculation of density for the remaining 10 materials for which pycnometry could not be done.


Assuntos
Cristalografia/métodos , Compostos Heterocíclicos/química , Simulação de Dinâmica Molecular , Cristalografia/tendências , Previsões , Compostos Heterocíclicos/análise , Simulação de Dinâmica Molecular/tendências
19.
Org Biomol Chem ; 18(7): 1279-1336, 2020 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-32025682

RESUMO

Enantio- and diastereodivergent routes to marine-origin natural products with different sizes of cyclic ethers and lactones have been used in order to assign stereochemical features. Kainoid amino acids such as isodomoic acids have been synthesized using diastereodivergent routes. The bis(indole) alkaloid dragmacidin F has been prepared by enantiodivergent strategies as well as furanoterpenes and the tetracyclic agelastatin A. Natural products containing five-membered lactones like quercus lactones, muricatacins, goniofufuranones, methylenolactocins and frenolicin B have been synthesized using stereodivergent routes. Macrolides are very abundant lactones and have been mainly prepared from the corresponding seco-acids by lactonization, such as lasiodiplodin, zaeralanes, macrosphelides and haloprins, or by ring-closing metathesis, such as aspercyclides, microcarpalides, macrolides FD-891 and 892, and tetradic-5-en-9-olides. Other natural products including cyclic ethers (such as sesamin, asarinin, acetogenins, centrolobines and nabilones), alcohols (such as sulcatol), esters (such as methyl jasmonates), polycyclic precursors of fredericamycin, amino alcohols (such as ambroxol and sphingosines), isoprostanes, isofurans, polyketide precursors of anachelins, brevicomins, gummiferol, shikimic acid and the related compounds, and the pheromone disparlure have been synthesized stereodivergently. Heterocyclic systems such as epoxides, theobroxides and bromoxones, oxetan-3-ones, 5- to 8-membered cyclic ethers, azetidones, γ-lactams, oxazolidinones, bis(oxazolines), dihydropyridoisoindolines and octahydroisoquinolines have been prepared following stereodivergent routes. Stereodivergent routes to unnatural compounds such as alkenes, dienes, allenes, cyclopropanes, alcohols, aldols, amines, amino alcohols, ß-amino acids, carboxylic acids, lactones, nitriles and α-amino nitriles have been considered as well.


Assuntos
Produtos Biológicos/síntese química , Compostos Heterocíclicos/síntese química , Lactonas/síntese química , Álcoois/síntese química , Álcoois/química , Alcenos/síntese química , Alcenos/química , Aminas/síntese química , Aminas/química , Aminoácidos/síntese química , Aminoácidos/química , Produtos Biológicos/química , Ácidos Carboxílicos/síntese química , Ácidos Carboxílicos/química , Compostos Heterocíclicos/química , Lactonas/química , Estrutura Molecular , Nitrilos/síntese química , Nitrilos/química , Estereoisomerismo
20.
Inorg Chem ; 59(5): 3312-3320, 2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-32049516

RESUMO

We carried out a detailed theoretical study on the mechanism of the carbene ligand substitution by cysteine and selenocysteine residues in an Au(I) bis-N-heterocyclic carbene complex in order to model the initial stages of the mechanism of action of this promising class of antitumor metallodrug. Both neutral and deprotonated capped Cys and Sec species were considered as possible nucleophiles in the ligand exchange reaction on the metal center to model the corresponding protein side chains. Energies and geometric structures of the possible transition states and reactant- and product-adducts involved in the substitution process have been calculated using density functional theory and local MP2. Reaction and activation enthalpies and free energies have been evaluated and indicate a slightly exothermic and exergonic process with reasonably low barriers, 21.3 and 19.6 kcal mol-1, respectively, for capped Cys and Sec, in good agreement with the experimental data available for the reaction with free amino acids. The results suggest a mechanism for the ligand exchange reaction involving an anionic thiolate or selenothiolate species coupled to an explicit proton transfer to the leaving carbene from the acidic component of the buffer. The presence of a buffer is necessary both in in vitro experiments and under physiological conditions, and its proton reservoir behavior reveals the importance of the environmental effects in carbene substitution by biological nucleophiles.


Assuntos
Antineoplásicos/química , Cisteína/química , Ouro/química , Compostos Heterocíclicos/química , Metano/análogos & derivados , Antineoplásicos/síntese química , Cisteína/análogos & derivados , Teoria da Densidade Funcional , Metano/química , Estrutura Molecular
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