RESUMEN
Selective ligands of the CB2 receptor are receiving considerable attention due to their potential as therapeutic agents for a variety of diseases. Recently, 7-hydroxy-5-oxopyrazolo[4,3-b]pyridine-6-carboxamide derivatives were shown to act at the CB2 receptor either as agonists or as inverse agonists/antagonists in vitro and to have anti-osteoarthritic activity in vivo. In this article, we report the synthesis, pharmacological profile, and molecular modeling of a series of twenty-three new 7-hydroxy-5-oxopyrazolo[4,3-b]pyridine-6-carboxamides with the aim of further developing this new class of selective CB2 ligands. In addition to these compounds, seven other analogs that had been previously synthesized were included in this study to better define the structure-activity relationship (SAR). Ten of the new compounds studied were found to be potent and selective ligands of the CB2 receptor, with Ki values ranging from 48.46 to 0.45 nM and CB1/CB2 selectivity indices (SI) ranging from >206 to >4739. In particular, compounds 54 and 55 were found to be high-affinity CB2 inverse agonists that were not active at all at the CB1 receptor, whereas 57 acted as an agonist. The functional activity profile of the compounds within this structural class depends mainly on the substitution pattern of the pyrazole ring.
Asunto(s)
Cannabinoides , Receptor Cannabinoide CB2 , Ligandos , Agonismo Inverso de Drogas , Relación Estructura-Actividad , Piridinas , Receptor Cannabinoide CB1RESUMEN
This review is aimed at providing an overview of the up-to-now published literature on resorc[4]arene macrocycles exploited as artificial receptors for the molecular recognition of some classes of natural products. A concise illustration of the main synthetic strategies developed to afford the resorc[4]arene scaffold is followed by a report on the principles of the gas-phase investigation of recognition phenomena by mass spectrometry (MS). Emphasis is placed on gas-phase studies of diastereoisomeric complexes generated inside a Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometer by resorc[4]arene receptors towards a series of natural products, namely amino acids, amphetamine, ethanolamine neurotransmitters, dipeptides, vinca alkaloids and nucleosides. The literature outcomes discussed here, taken largely from our own revisited work, have been completed by references to other studies, in order to draw a broader picture of this rapidly evolving field of research.
Asunto(s)
Productos Biológicos/análisis , Productos Biológicos/química , Hidrocarburos/química , Resorcinoles/química , Humanos , Estructura Molecular , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
Prokineticins are angiogenic hormones that activate two G protein-coupled receptors: PKR1 and PKR2. PKR1 has emerged as a critical mediator of cardiovascular homeostasis and cardioprotection. Identification of non-peptide PKR1 agonists that contribute to myocardial repair and collateral vessel growth hold promises for treatment of heart diseases. Through a combination of in silico studies, medicinal chemistry, and pharmacological profiling approaches, we designed, synthesized, and characterized the first PKR1 agonists, demonstrating their cardioprotective activity against myocardial infarction (MI) in mice. Based on high throughput docking protocol, 250,000 compounds were computationally screened for putative PKR1 agonistic activity, using a homology model, and 10 virtual hits were pharmacologically evaluated. One hit internalizes PKR1, increases calcium release and activates ERK and Akt kinases. Among the 30 derivatives of the hit compound, the most potent derivative, IS20, was confirmed for its selectivity and specificity through genetic gain- and loss-of-function of PKR1. Importantly, IS20 prevented cardiac lesion formation and improved cardiac function after MI in mice, promoting proliferation of cardiac progenitor cells and neovasculogenesis. The preclinical investigation of the first PKR1 agonists provides a novel approach to promote cardiac neovasculogenesis after MI.
Asunto(s)
Benzamidas/química , Sustancias Protectoras/química , Piridinas/química , Receptores Acoplados a Proteínas G/agonistas , Animales , Benzamidas/farmacología , Benzamidas/uso terapéutico , Sitios de Unión , Presión Sanguínea/efectos de los fármacos , Células CHO , Calcio/metabolismo , Células Cultivadas , Biología Computacional , Cricetinae , Cricetulus , Modelos Animales de Enfermedad , Ecocardiografía , Células Endoteliales/citología , Células Endoteliales/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Microscopía Confocal , Simulación del Acoplamiento Molecular , Infarto del Miocardio/tratamiento farmacológico , Infarto del Miocardio/metabolismo , Infarto del Miocardio/patología , Péptidos/química , Sustancias Protectoras/farmacología , Sustancias Protectoras/uso terapéutico , Piridinas/farmacología , Piridinas/uso terapéutico , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Transducción de Señal/efectos de los fármacosRESUMEN
The 5-amino-1,2,3-triazole-4-carboxylic acid is a suitable molecule for the preparation of collections of peptidomimetics or biologically active compounds based on the triazole scaffold. However, its chemistry may be influenced by the possibility of undergoing the Dimroth rearrangement. To overcome this problem, a protocol based on the ruthenium-catalyzed cycloaddition of N-Boc ynamides with azides has been developed to give a protected version of this triazole amino acid. When aryl or alkyl azides are reacted with N-Boc-aminopropiolates or arylynamides, the cycloaddition occurs with complete regiocontrol, while N-Boc-alkyl ynamides yield a mixture of regioisomers. The prepared amino acids were employed for the preparation of triazole-containing dipeptides having the structural motives typical of turn inducers. In addition, triazoles active as HSP90 inhibitors (as compound 41, IC50 = 29 nM) were synthesized.
Asunto(s)
Aminoácidos/química , Azidas/química , Ácidos Carboxílicos/química , Dipéptidos/química , Proteínas HSP90 de Choque Térmico/química , Peptidomiméticos/química , Rutenio/química , Triazoles/síntesis química , Catálisis , Reacción de Cicloadición , Proteínas HSP90 de Choque Térmico/agonistas , Proteínas HSP90 de Choque Térmico/antagonistas & inhibidores , Concentración 50 Inhibidora , Triazoles/química , Triazoles/farmacologíaRESUMEN
G protein-coupled receptors (GPCRs) are seven integral transmembrane proteins that are the primary targets of almost 30% of approved drugs and continue to represent a major focus of pharmaceutical research. All of GPCR targeted medicines were discovered by classical medicinal chemistry approaches. After the first GPCR crystal structures were determined, the docking screens using these structures lead to discovery of more novel and potent ligands. There are over 360 pharmaceutically relevant GPCRs in the human genome and to date about only 30 of structures have been determined. For these reasons, computational techniques such as homology modeling and molecular dynamics simulations have proven their usefulness to explore the structure and function of GPCRs. Furthermore, structure-based drug design and in silico screening (High Throughput Docking) are still the most common computational procedures in GPCRs drug discovery. Moreover, ligand-based methods such as three-dimensional quantitative structure-selectivity relationships, are the ideal molecular modeling approaches to rationalize the activity of tested GPCR ligands and identify novel GPCR ligands. In this review, we discuss the most recent advances for the computational approaches to effectively guide selectivity and affinity of ligands. We also describe novel approaches in medicinal chemistry, such as the development of biased agonists, allosteric modulators, and bivalent ligands for class A GPCRs. Furthermore, we highlight some knockout mice models in discovering biased signaling selectivity.
RESUMEN
Targeted molecular dynamics (TMD) simulations allowed for identifying the chemical/structural features of the nucleotide-competitive HIV-1 inhibitor DAVP-1, which is responsible for the disruption of the T-shape motif between Try183 and Trp229 of the reverse transcriptase (RT). DAVP-1 promoted the opening of a connection "gate" between allosteric and catalytic sites of HIV-1 RT, thus explaining its peculiar mechanism of action and providing useful insights to develop novel nucleotide-competitive RT inhibitors.
Asunto(s)
Transcriptasa Inversa del VIH/química , VIH-1/química , Simulación del Acoplamiento Molecular , Simulación de Dinámica Molecular , Pirimidinas/química , Inhibidores de la Transcriptasa Inversa/química , Compuestos de Vinilo/química , Sitio Alostérico , Unión Competitiva , Dominio Catalítico , Transcriptasa Inversa del VIH/antagonistas & inhibidores , VIH-1/enzimología , Compuestos Heterocíclicos con 3 Anillos/química , Humanos , Indoles/química , Nitrilos/química , Unión Proteica , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Piridonas/química , Relación Estructura-ActividadRESUMEN
Bis(diamido)-bridged basket resorcin[4]arene (all-S)-1 and its (all-R)-1 enantiomer proved able to interact with 2'-deoxycytidine (2) and pyrimidine nucleoside analogs in dimethyl sulfoxide (DMSO) solution. In such a solvent, the resorcinarene hosts adopt a preferential 1,3-alternate-like conformation, with a larger cavity delimited by two syn 3,5-dimethoxyphenyl moieties, and two external pockets, each delimited by the other 3,5-dimethoxyphenyl group and its diamido arm (the wing). Complexation phenomena were investigated by nuclear magnetic resonance (NMR) methods, including (1)H NMR DOSY and 1D ROESY experiments, and molecular modeling. Heteroassociation constants of [(all-S)-1·2] and [(all-R)-1·2] diastereoisomeric complexes were obtained from diffusion data by single point measurements, and from nonlinear fitting of 1H NMR chemical shifts. Selective proton relaxation rate measurements allowed us to significantly discriminate the two complexes by identifying two different interaction sites of the guest in the resorcin[4]arene host, depending on its configuration.
Asunto(s)
Calixarenos/química , Desoxicitidina/química , Modelos Moleculares , Fenilalanina/análogos & derivados , Espectroscopía de Resonancia Magnética , Fenilalanina/química , EstereoisomerismoRESUMEN
The development of a novel approach for the prediction of antiestrogenic activity is described, bringing up to date a previous pharmacophore study. Software Phase has been used to derive a 3D-QSAR model based, as alignment rule, on a pharmacophore built on three compounds highly active against MCF-7 cell line. Five features comprised the pharmacophore: two hydrogen-bond acceptors, one hydrogen-bond donor, and two aromatic rings. The sequential 3D-QSAR yielded a test set q(2) equal to 0.73 and proved to be predictive with respect to an external test set of 21 compounds (r(2) = 0.69). The model was used to detect new MCF-7 inhibitors through 3D-database searching and identified fourteen compounds that were subsequently tested in vitro against the MCF-7 human breast adenocarcinoma cell line. Eleven out of the fourteen compounds exhibited inhibitory activity with IC50 values ranging between 30 and 186 µM. The results of the study confirmed the fundamental validity of the chosen approach as a hit discovery tool.
Asunto(s)
Antineoplásicos/farmacología , Descubrimiento de Drogas , Ensayos Analíticos de Alto Rendimiento , Relación Estructura-Actividad Cuantitativa , Antineoplásicos/síntesis química , Antineoplásicos/química , Proliferación Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Células MCF-7 , Estructura Molecular , Relación Estructura-ActividadRESUMEN
A mild chlorination reaction of alcohols was developed using the classical thionyl chloride reagent but with added catalytic titanium(IV) chloride. These reactions proceeded rapidly to afford chlorination products in excellent yields and with preference for retention of configuration. Stereoselectivities were high for a variety of chiral cyclic secondary substrates including sterically hindered systems. Chlorosulfites were first generated in situ and converted to alkyl chlorides by the action of titanium tetrachloride which is thought to chelate the chlorosulfite leaving group and deliver the halogen nucleophile from the front face. To better understand this novel reaction pathway, an ab initio study was undertaken at the DFT level of theory using two different computational approaches. This computational evidence suggests that while the reaction proceeds through a carbocation intermediate, this charged species likely retains pyramidal geometry existing as a conformational isomer stabilized through hyperconjugation (hyperconjomers). These carbocations are then essentially "frozen" in their original configurations at the time of nucleophilic capture.
Asunto(s)
Alcoholes/química , Cationes/química , Titanio/química , Catálisis , Halogenación , Indicadores y Reactivos/química , Cinética , Estructura Molecular , Teoría Cuántica , EstereoisomerismoRESUMEN
In our search for new cannabinoid receptor modulators, we describe herein the design and synthesis of three sets of indole-based ligands characterized by an acetamide, oxalylamide, or carboxamide chain, respectively. Most of the compounds showed affinity for CB2 receptors in the nanomolar range, with K(i) values spanning 3 orders of magnitude (377-0.37 nM), and moderate to good selectivity over CB1 receptors. Their in vitro functional activity as inverse agonists was confirmed in vivo in the formalin test of acute peripheral and inflammatory pain in mice, in which compounds 10a and 11e proved to be able to reverse the effect of the CB2 selective agonist COR167.
Asunto(s)
Amidas/síntesis química , Indoles/síntesis química , Receptor Cannabinoide CB2/antagonistas & inhibidores , Amidas/química , Amidas/farmacología , Animales , Células CHO , Técnicas Químicas Combinatorias , Cricetinae , Cricetulus , AMP Cíclico/biosíntesis , Diseño de Fármacos , Agonismo Inverso de Drogas , Células HEK293 , Humanos , Factores Inmunológicos/síntesis química , Factores Inmunológicos/química , Factores Inmunológicos/farmacología , Indoles/química , Indoles/farmacología , Inflamación/tratamiento farmacológico , Ratones , Modelos Moleculares , Dolor/tratamiento farmacológico , Dolor/inmunología , Dimensión del Dolor , Ensayo de Unión Radioligante , Receptor Cannabinoide CB2/agonistas , Relación Estructura-ActividadRESUMEN
Three heterocyclic systems were selected as potential bioisosteres of the amide linker for a series of 1,6-disubstituted-4-quinolone-3-carboxamides, which are potent and selective CB2 ligands that exhibit poor water solubility, with the aim of improving their physicochemical profile and also of clarifying properties of importance for amide bond mimicry. Among the newly synthesized compounds, a 1,2,3-triazole derivative (1-(adamantan-1-yl)-4-[6-(furan-2-yl)-1,4-dihydro-4-oxo-1-pentylquinolin-3-yl]-1H-1,2,3-triazole) emerged as the most promising in terms of both physicochemical and pharmacodynamic properties. When assayed in vitro, this derivative exhibited inverse agonist activity, whereas, in the formalin test in mice, it produced analgesic effects antagonized by a well-established inverse agonist. Metabolic studies allowed the identification of a side chain hydroxylated derivative as its only metabolite, which, in its racemic form, still showed appreciable CB2 selectivity, but was 150-fold less potent than the parent compound.
Asunto(s)
4-Quinolonas/química , Ácidos Carboxílicos/química , Simulación por Computador , Receptor Cannabinoide CB2/agonistas , Animales , Células CHO , Línea Celular Tumoral , Cromatografía Líquida de Alta Presión , Cricetinae , Cricetulus , Humanos , Ligandos , Lípidos/química , Ratones , Modelos Moleculares , Estructura Molecular , Estructura Terciaria de Proteína , Solubilidad , Relación Estructura-ActividadRESUMEN
The potential efficacy of GABA(B) receptor agonists in the treatment of pain, drug addiction, epilepsy, cognitive dysfunctions, and anxiety disorders is supported by extensive preclinical and clinical evidence. However, the numerous side effects produced by the GABA(B) receptor agonist baclofen considerably limit the therapeutic use of this compound. The identification of positive allosteric modulators (PAMs) of the GABA(B) receptor may constitute a novel approach in the pharmacological manipulation of the GABA(B) receptor, leading to fewer side effects. The present study reports the identification of two novel compounds, methyl 2-(1-adamantanecarboxamido)-4-ethyl-5-methylthiophene-3-carboxylate (COR627) and methyl 2-(cyclohexanecarboxamido)-4-ethyl-5-methylthiophene-3-carboxylate (COR628), which act as GABA(B) PAMs in 1) rat cortical membranes and 2) in vivo assay. Both compounds potentiated GABA- and baclofen-stimulated guanosine 5'-O-(3-[(35)S]thio)-triphosphate binding to native GABA(B) receptors, while producing no effect when given alone. GABA concentration-response curves in the presence of fixed concentrations of COR627 and COR628 revealed an increase of potency of GABA rather than its maximal efficacy. In radioligand binding experiments [displacement of the GABA(B) receptor antagonist, 3-N-[1-((S)-3,4dichlorophenyl)-ethylaminol]-2-(S)hydroxypropyl cyclo-hexylmethyl phosphinic acid ([(3)H]CGP54626)], both COR627 and COR628 increased the affinity of high- and low-affinity binding sites for GABA, producing no effect when administered alone up to a concentration of 1 mM. In vivo experiments indicated that pretreatment with per se ineffective doses of COR627 and COR628 potentiated the sedative/hypnotic effect of baclofen. In conclusion, COR627 and COR628 may represent two additional tools for use in investigating the roles and functions of positive allosteric modulatory binding sites of the GABA(B) receptor.
Asunto(s)
Adamantano/análogos & derivados , Moduladores del GABA/farmacología , Receptores de GABA-B/fisiología , Tiofenos/farmacología , Adamantano/farmacología , Regulación Alostérica/efectos de los fármacos , Animales , Baclofeno/farmacología , Sitios de Unión , Guanosina 5'-O-(3-Tiotrifosfato)/metabolismo , Masculino , Ratones , Ratones Endogámicos DBA , Pentobarbital/farmacología , Ratas , Ratas Sprague-DawleyRESUMEN
This paper deals with the design, synthesis, and evaluation of a new series of receptors for protein surface recognition. The design of these agents is based around the attachment of four constrained dipeptide chains onto a central resorc[4]arene scaffold. By varying the sequence, nature, and stereochemistry of the chains we prepared anionically functionalized N-linked peptidoresorc[4]arenes 12, 13, and 17 by Pd/C-catalyzed hydrogenation of the corresponding benzyl esters 10, 11, and 16. From this family of receptors we have identified noncompetitive inhibitors of α-chymotrypsin (ChT), which function by binding to the surface of the enzyme in the neighborhood of the active site cleft (K(i) values ranging from 12.4 ± 5.1 µM for free carboxylic acid (+)-12b to 0.76 ± 0.14 µM for benzyl ester (-)-16a). For anionically functionalized receptors 12, 13, and 17 the ChT inhibition is based essentially on electrostatic interaction, and the bound enzyme can be released from the resorcarene surface by increasing the ionic strength, with its activity almost completely restored. For receptors with terminal benzyl ester groups (10 and 16) a hydrophobic network can be suggested.
Asunto(s)
Calixarenos/química , Quimotripsina/antagonistas & inhibidores , Nitrógeno/química , Péptidos Cíclicos/química , Péptidos Cíclicos/farmacología , Fenoles/química , Inhibidores de Proteasas/química , Inhibidores de Proteasas/farmacología , Animales , Dominio Catalítico , Bovinos , Quimotripsina/química , Evaluación Preclínica de Medicamentos , Humanos , Modelos Moleculares , Concentración Osmolar , Péptidos Cíclicos/síntesis química , Péptidos Cíclicos/metabolismo , Inhibidores de Proteasas/síntesis química , Inhibidores de Proteasas/metabolismo , Albúmina Sérica/metabolismo , Estereoisomerismo , Especificidad por SustratoRESUMEN
This paper describes a three-dimensional quantitative structure-selectivity relationships (3D-QSSR) study for selectivity of a series of ligands for cannabinoid CB1 and CB2 receptors. 3D-QSSR exploration was expected to provide design information for drugs with high selectivity toward the CB2 receptor. The proposed 3D computational model was performed by Phase and generated taking into account a number of structurally diverse compounds characterized by a wide range of selectivity index values. The model proved to be predictive, with r2 of 0.95 and Q2 of 0.63. In order to get prospective experimental validation, the selectivity of an external data set of 39 compounds reported in the literature was predicted. The correlation coefficient (r2=0.56) obtained on this unrelated test set provided evidence that the correlation shown by the model was not a chance result. Subsequently, we essayed the ability of our approach to help the design of new CB2-selective ligands. Accordingly, based on our interest in studying the cannabinergic properties of quinolones, the N-(adamantan-1-yl)-4-oxo-8-methyl-1-pentyl-1,4-dihydroquinoline-3-carboxamide (65) was considered as a potential synthetic target. The log(SI) value predicted by using our model was indicative of high CB2 selectivity for such a compound, thus spurring us to synthesize it and to evaluate its CB1 and CB2 receptor affinity. Compound 65 was found to be an extremely selective CB2 ligand as it displayed high CB2 affinity (Ki=4.9 nM), while being devoid of CB1 affinity (Ki>10,000 nM). The identification of a new selective CB2 receptor ligand lends support for the practicability of quantitative ligand-based selectivity models for cannabinoid receptors. These drug discovery tools might represent a valuable complementary approach to docking studies performed on homology models of the receptors.
Asunto(s)
Diseño de Fármacos , Relación Estructura-Actividad Cuantitativa , Quinolonas/farmacología , Receptor Cannabinoide CB1/antagonistas & inhibidores , Receptor Cannabinoide CB2/antagonistas & inhibidores , Simulación por Computador , Humanos , Ligandos , Modelos Moleculares , Estructura Molecular , Quinolonas/síntesis química , Quinolonas/química , Proteínas Recombinantes/antagonistas & inhibidores , EstereoisomerismoRESUMEN
A ligand-based pharmacophore approach for the prediction of antiestrogenic activity to be used as an in silico screening tool for bioactive compounds including natural products was developed using Catalyst HypoGen. The generated pharmacophore hypothesis (HYPO-7) consisted of five features, namely, one hydrophobic (HY1), two hydrophobic aromatic (HY2), one hydrogen-bond acceptor (HBA), and one hydrogen-bond donor (HBD). HYPO-7 successfully predicted the lack of cytotoxicity of a number of new metabolites isolated from the red alga Laurencia glandulifera. Furthermore, a screening of the Asinex Gold Collection database was performed by coupling HYPO-7 with a docking filtration, which resulted in a restricted set of 12 new scaffolds to be investigated as potential SERMs. The inhibitory activity of these compounds was evaluated in vitro using MCF7 human breast adenocarcinoma cell line. Ten out of the twelve compounds exhibited inhibitory activity with IC(50) values between 26 and 188 microM. This result shows that application of HYPO-7 could assist in the selection of potentially active compounds, thus expediting the hit discovery process.
Asunto(s)
Moduladores de los Receptores de Estrógeno/farmacología , Modelos Químicos , Moduladores de los Receptores de Estrógeno/química , Enlace de Hidrógeno , Rhodophyta/químicaRESUMEN
A dynamic target-based pharmacophoric model mapping the CD4 binding site on HIV-1 gp120 was built and used to identify new hits able to inhibit gp120-CD4 protein-protein interactions. Two compounds showed micromolar inhibition of HIV-1 replication in cells attributable to an interference with the entry step of infection, by direct interaction with gp120. Inactivity of compounds toward a M475I strain suggested specific contacts with the Phe43 cavity of gp120.
Asunto(s)
Fármacos Anti-VIH/química , Antígenos CD4/metabolismo , Proteína gp120 de Envoltorio del VIH/metabolismo , VIH-1/efectos de los fármacos , Fenilpropionatos/química , Ftalimidas/química , Fármacos Anti-VIH/toxicidad , Sitios de Unión , Antígenos CD4/química , Línea Celular , Simulación por Computador , Proteína gp120 de Envoltorio del VIH/química , Humanos , Modelos Químicos , Fenilpropionatos/toxicidad , Ftalimidas/toxicidad , Dominios y Motivos de Interacción de Proteínas , Mapeo de Interacción de Proteínas , Replicación Viral/efectos de los fármacosRESUMEN
The stereoselectivity of the reaction between (R)-(-)-2-butylamine and the diastereomeric proton-bound complexes of (+)-catharanthine (C) or (-)-vindoline (V) with some chiral amido[4]resorcinarenes has been investigated in the gas phase by ESI-FT-ICR-MS. The reaction stereoselectivity (0.56 < k(homo)/k(hetero) < 16.9) is found to depend critically on the functional groups present in the chiral pendants of the hosts. Rationalisation of the kinetic results is based on careful computational and spectroscopic studies of the most stable conformations of (+)-catharanthine and its protonated form in the isolated state and in water, as well as in a representative host structure. The emerging picture points to the relevant diastereomeric proton-bound complexes as quasi-degenerate, thus suggesting that their stereoselectivity in the guest exchange reaction is mostly due to kinetic factors. The results of this study may represent a starting point for a deeper comprehension of the intrinsic factors that endow these molecules, and their dimeric forms, with their biochemical properties.
Asunto(s)
Aminas/química , Calixarenos/química , Fenilalanina/análogos & derivados , Alcaloides de la Vinca/química , Carbono/química , Hidrocarburos/química , Cinética , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Modelos Moleculares , Estructura Molecular , Fenilalanina/química , Espectroscopía Infrarroja por Transformada de Fourier , EstereoisomerismoRESUMEN
Carbapenem-hydrolyzing class D beta-lactamases (CHDLs) are enzymes found in important Gram-negative pathogens (mainly Acinetobacter baumannii and Enterobacteriaceae) that confer resistance to beta-lactam antibiotics, and notably carbapenems. The crystal structure of the OXA-48 carbapenemase was determined at pH 7.5 and at a resolution of 1.9 A. Surprisingly, and by contrast with OXA-24, the only other CHDL of known crystal structure, the structure of OXA-48 was similar to OXA-10, an enzyme devoid of carbapenemase activity, indicating that the hydrolysis of these compounds could depend on subtle changes in the active site region. Moreover, the active site groove of OXA-48 was different from that of OXA-24 in shape, dimensions, and charge distribution. Molecular dynamics pointed to the functional relevance of residues located in or close to the beta5-beta6 loop and allowed us to propose a mechanism for carbapenem hydrolysis by OXA-48.
Asunto(s)
beta-Lactamasas/química , Proteínas Bacterianas/química , Proteínas Bacterianas/clasificación , Dominio Catalítico , Simulación por Computador , Cristalografía por Rayos X , Cinética , Estructura Cuaternaria de Proteína , beta-Lactamasas/clasificaciónRESUMEN
The intramolecular version of the Huisgen cycloaddition is a potentially useful reaction for the stereocontrolled preparation of 1,5-disubstituted and 1,4,5-trisubstiututed triazoles. When alpha-azido propargyl esters derived from alpha-amino acids are submitted to [3 + 2] cycloaddition, the expected 4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-6-ones are not formed; rather, an oligomeric cyclic polyester is obtained via a prevailing intermolecular cycloaddition. We have discovered that propargyl alpha-azido amides undergo metal-free intramolecular Huisgen cycloaddition in MeCN/H(2)O under microwave dielectric heating. This reaction provides access to new condensed triazoles that can be considered as conformationally constrained peptidomimetics. Moreover, the following microwave-assisted lactam ring opening provides 1,4-disubstituted and 1,4,5-trisubstituted triazole amino acids. The same kind of compounds are obtained from the ester cycloadduct by reaction with primary amines in the presence of AlMe(3). In order to interpretate this unpredictable behavior, an ab initio study of the reaction pathway was undertaken using GAMESS(US) at the B3LYP/6-31G** level of theory. Different relaxed potential energy profiles were obtained for esters and amides, suggesting that the cis-arrangement of the -CO=N- could account for the amide reactivity.