RESUMEN
The Pictet-Spengler reaction of tryptophan esters and aldehydes has been widely applied in natural product synthesis and medicinal chemistry. To date, the trans- or cis-configuration of 1,3-disubstituted tetrahydro-ß-carbolines (THßCs) formed in this reaction has most often been assigned based on the relative 13C chemical shifts of C1 and C3 in the diastereomers. Although the upfield shifts of C1 and C3 in trans-THßCs relative to cis-THßCs has been attributed to steric compression associated with the "γ-gauche" effect, we show that this effect is not borne out experimentally for other carbons that should suffer this same compression. Thus we developed a robust alternative method for stereochemical assignment based on 1H NMR coupling constants (31 examples) and supported by extensive DFT-based conformational analysis and calculation of 1H-1H coupling constants. DFT calculations of 13C NMR chemical shifts also cast doubt upon the role of the "γ-gauche" effect on C1 and C3 chemical shifts in trans-THßCs.
Asunto(s)
Carbolinas/química , Modelos Moleculares , Espectroscopía de Protones por Resonancia Magnética , Teoría Cuántica , EstereoisomerismoRESUMEN
Coxiella burnetii is a highly infectious bacterium and potential agent of bioterrorism. However, it has not been studied as extensively as other biological agents, and very few of its proteins have been structurally characterized. To address this situation, we undertook a study of critical metabolic enzymes in C. burnetii that have great potential as drug targets. We used high-throughput techniques to produce novel crystal structures of 48 of these proteins. We selected one protein, C. burnetii dihydrofolate reductase (CbDHFR), for additional work to demonstrate the value of these structures for structure-based drug design. This enzyme's structure reveals a feature in the substrate binding groove that is different between CbDHFR and human dihydrofolate reductase (hDHFR). We then identified a compound by in silico screening that exploits this binding groove difference, and demonstrated that this compound inhibits CbDHFR with at least 25-fold greater potency than hDHFR. Since this binding groove feature is shared by many other prokaryotes, the compound identified could form the basis of a novel antibacterial agent effective against a broad spectrum of pathogenic bacteria.
Asunto(s)
Proteínas Bacterianas/química , Coxiella burnetii/efectos de los fármacos , Coxiella burnetii/genética , Antagonistas del Ácido Fólico/farmacología , Ensayos Analíticos de Alto Rendimiento/métodos , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Sitios de Unión , Simulación por Computador , Cristalografía por Rayos X , Diseño de Fármacos , Antagonistas del Ácido Fólico/química , Humanos , Conformación Proteica , Tetrahidrofolato Deshidrogenasa/químicaRESUMEN
Compounds that target isoprenoid biosynthesis in Plasmodium falciparum could be a welcome addition to malaria chemotherapy, since the methylerythritol phosphate (MEP) pathway used by the parasite is not present in humans. We previously reported that MMV008138 targets the apicoplast of P. falciparum and that its target in the MEP pathway differs from that of Fosmidomycin. In this Letter, we determine that the active stereoisomer of MMV008138 is 4a, which is (1R,3S)-configured. 2',4'-Disubstitution of the D ring was also found to be crucial for inhibition of the parasite growth. Limited variation of the C3-carboxylic acid substituent was carried out, and methylamide derivative 8a was found to be more potent than 4a; other amides, acylhydrazines, and esters were less potent. Finally, lead compounds 4a, 4e, 4f, 4h, 8a, and 8e did not inhibit growth of Escherichia coli, suggesting that protozoan-selective inhibition of the MEP pathway of P. falciparum can be achieved.
Asunto(s)
Antimaláricos/farmacología , Carbolinas/farmacología , Eritritol/análogos & derivados , Ácidos Pipecólicos/farmacología , Plasmodium falciparum/efectos de los fármacos , Fosfatos de Azúcar/antagonistas & inhibidores , Antimaláricos/química , Carbolinas/química , Relación Dosis-Respuesta a Droga , Eritritol/antagonistas & inhibidores , Eritritol/metabolismo , Estructura Molecular , Pruebas de Sensibilidad Parasitaria , Ácidos Pipecólicos/química , Plasmodium falciparum/crecimiento & desarrollo , Plasmodium falciparum/metabolismo , Estereoisomerismo , Relación Estructura-Actividad , Fosfatos de Azúcar/metabolismoRESUMEN
We previously reported that activation of p53 by APR-246 reprograms tumor-associated macrophages to overcome immune checkpoint blockade resistance. Here, we demonstrate that APR-246 and its active moiety, methylene quinuclidinone (MQ) can enhance the immunogenicity of tumor cells directly. MQ treatment of murine B16F10 melanoma cells promoted activation of melanoma-specific CD8+ T cells and increased the efficacy of a tumor cell vaccine using MQ-treated cells even when the B16F10 cells lacked p53. We then designed a novel combination of APR-246 with the TLR-4 agonist, monophosphoryl lipid A, and a CD40 agonist to further enhance these immunogenic effects and demonstrated a significant antitumor response. We propose that the immunogenic effect of MQ can be linked to its thiol-reactive alkylating ability as we observed similar immunogenic effects with the broad-spectrum cysteine-reactive compound, iodoacetamide. Our results thus indicate that combination of APR-246 with immunomodulatory agents may elicit effective antitumor immune response irrespective of the tumor's p53 mutation status.
Asunto(s)
Linfocitos T CD8-positivos , Melanoma , Ratones , Animales , Proteína p53 Supresora de Tumor/genética , Antígenos de NeoplasiasRESUMEN
Perivascular collagen deposition by activated fibroblasts promotes vascular stiffening and drives cardiovascular diseases such as pulmonary hypertension (PH). Whether and how vascular fibroblasts rewire their metabolism to sustain collagen biosynthesis remains unknown. Here, we found that inflammation, hypoxia, and mechanical stress converge on activating the transcriptional coactivators YAP and TAZ (WWTR1) in pulmonary arterial adventitial fibroblasts (PAAFs). Consequently, YAP and TAZ drive glutamine and serine catabolism to sustain proline and glycine anabolism and promote collagen biosynthesis. Pharmacologic or dietary intervention on proline and glycine anabolic demand decreases vascular stiffening and improves cardiovascular function in PH rodent models. By identifying the limiting metabolic pathways for vascular collagen biosynthesis, our findings provide guidance for incorporating metabolic and dietary interventions for treating cardiopulmonary vascular disease.
Asunto(s)
Glutamina , Serina , Rigidez Vascular , Animales , Glutamina/metabolismo , Serina/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Fibroblastos/metabolismo , Hipertensión Pulmonar/metabolismo , Hipertensión Pulmonar/patología , Humanos , Colágeno/metabolismo , RatasRESUMEN
Theoretical studies of the mechanisms of the thermal cyclotrimerization of fluoro- and chloroacetylenes, which were reported by Viehe and Ballester, respectively, were conducted with the aid of density functional theory calculations of the (U)B3LYP functional, indicating that the thermal cyclotrimerizations of fluoro- and chloroacetylenes involve tandem processes of regioselectively stepwise [2+2] and stepwise [4+2] cycloadditions. These tandem processes generate 1,2,6-trihalo-Dewar benzenes and 1,2,4-trihalo-Dewar benzenes, which then isomerize to the corresponding benzenes when heated. The rate-determining step of the cyclotrimerizations of haloacetylenes is the dimerization step involving open-shell singlet diradical transition states and intermediates. The substituent effects in the thermal cyclotrimerization of haloacetylenes have been rationalized using frontier molecular orbital theory. The higher reactivity of fluoroacetylenes compared to that of chloroacetylenes is due to the fact that fluoroacetylenes have lower singlet-triplet gaps than chloroacetylenes and more easily undergo dimerization and cyclotrimerization. In this report, additional experiments were performed to verify the theoretical prediction about the cyclotrimerization of chloroacetylene and to trap the proposed 1,4-dichlorocyclobutadiene intermediate. Experiments revealed that the thermal reaction of phenylchloroacetylene at 110 °C gave 1,2,3-triphenyltrichlorobenzene and 1,2,4-triphenyltrichlorobenzene together with a tetramer, cis-1,2,5,6-tetrachloro-3,4,7,8-tetraphenyltricyclo[4.2.0.0(2,5)]octa-3,7-diene. The proposed 1,4-diphenyldichlorocyclobutadiene intermediate in the thermal cyclotrimerization of phenylchloroacetylene was successfully trapped using dienophiles of maleic anhydride and dimethyl acetylenedicarboxylate.
RESUMEN
Malaria continues to be one of the deadliest diseases worldwide, and the emergence of drug resistance parasites is a constant threat. Plasmodium parasites utilize the methylerythritol phosphate (MEP) pathway to synthesize isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), which are essential for parasite growth. Previously, we and others identified that the Malaria Box compound MMV008138 targets the apicoplast and that parasite growth inhibition by this compound can be reversed by supplementation of IPP. Further work has revealed that MMV008138 targets the enzyme 2- C-methyl-d-erythritol 4-phosphate cytidylyltransferase (IspD) in the MEP pathway, which converts MEP and cytidine triphosphate (CTP) to cytidinediphosphate methylerythritol (CDP-ME) and pyrophosphate. In this work, we sought to gain insight into the structure-activity relationships by probing the ability of MMV008138 analogs to inhibit PfIspD recombinant enzyme. Here, we report PfIspD inhibition data for fosmidomycin (FOS) and 19 previously disclosed analogs and report parasite growth and PfIspD inhibition data for 27 new analogs of MMV008138. In addition, we show that MMV008138 does not target the recently characterized human IspD, reinforcing MMV008138 as a prototype of a new class of species-selective IspD-targeting antimalarial agents.
Asunto(s)
Antimaláricos/farmacología , Carbolinas/farmacología , Inhibidores Enzimáticos/farmacología , Nucleotidiltransferasas/antagonistas & inhibidores , Ácidos Pipecólicos/farmacología , Plasmodium/efectos de los fármacos , Plasmodium/enzimología , Antimaláricos/química , Carbolinas/química , Inhibidores Enzimáticos/química , Estructura Molecular , Ácidos Pipecólicos/química , Plasmodium/crecimiento & desarrollo , Relación Estructura-ActividadRESUMEN
N1-Methyl-N4-Boc-benzo[e][1,4]diazepine-2,5-diones were prepared in good yield and high stereochemical purity from five amino acids. Upon deprotonation, these compounds undergo ring contraction to the corresponding quinolone-2,4-diones with high enantioselectivity, providing efficient entry to a potentially useful drug scaffold. Mechanistic commentary and comparisons to related reactions are provided.
Asunto(s)
Azepinas/síntesis química , Cetonas/síntesis química , Quinolonas/síntesis química , Azepinas/química , Catálisis , Cetonas/química , Estructura Molecular , Quinolonas/química , EstereoisomerismoRESUMEN
Developing olefin isomerization reactions to reach kinetically controlled Z-alkenes is challenging because formation of trans-alkenes is thermodynamically favored under the traditional catalytic conditions using acids, bases, or transition metals as the catalysts. A new synthesis of Z-alkenes from Rh(I)-catalyzed olefin isomerization of ß,γ-unsaturated ketones to α,ß-unsaturated ketones was developed, providing an easy and efficient way to access various Z-enones.
RESUMEN
Discovering new carbon building blocks is very significant to advance transition-metal-catalyzed cycloadditions for the synthesis of various-sized ring compounds. A new seven-carbon building block from buta-1,3-dienylcyclopropanes (BDCPs) has been developed, showing that, under the catalysis of [Rh(CO)(2)Cl](2), BDCPs react with CO to give [7 + 1] cycloaddition products, cyclooctadienones. The present [7 + 1] reaction provides an efficient entry to the synthetically challenging eight-membered carbocyclic skeleton, which is present in many natural products of medicinal and biological significance.