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1.
J Xray Sci Technol ; 32(1): 1-15, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-37927293

RESUMEN

BACKGROUND: In clinical medicine, low-dose radiographic image noise reduces the quality of the detected image features and may have a negative impact on disease diagnosis. OBJECTIVE: In this study, Adaptive Projection Network (APNet) is proposed to reduce noise from low-dose medical images. METHODS: APNet is developed based on an architecture of the U-shaped network to capture multi-scale data and achieve end-to-end image denoising. To adaptively calibrate important features during information transmission, a residual block of the dual attention method throughout the encoding and decoding phases is integrated. A non-local attention module to separate the noise and texture of the image details by using image adaptive projection during the feature fusion. RESULTS: To verify the effectiveness of APNet, experiments on lung CT images with synthetic noise are performed, and the results demonstrate that the proposed approach outperforms recent methods in both quantitative index and visual quality. In addition, the denoising experiment on the dental CT image is also carried out and it verifies that the network has a certain generalization. CONCLUSIONS: The proposed APNet is an effective method that can reduce image noise and preserve the required image details in low-dose radiographic images.


Asunto(s)
Algoritmos , Tomografía Computarizada por Rayos X , Relación Señal-Ruido , Dosis de Radiación , Tomografía Computarizada por Rayos X/métodos , Procesamiento de Imagen Asistido por Computador/métodos
2.
BMC Gastroenterol ; 23(1): 353, 2023 Oct 11.
Artículo en Inglés | MEDLINE | ID: mdl-37821801

RESUMEN

BACKGROUND: Replication factor C subunit 2 (RFC2) participates in the growth and metastasis of various malignancies. Our study investigated the roles of RFC2 in colorectal cancer (CRC). RESULTS: RFC2 expression was upregulated in CRC tissues and cells. High RFC2 expression was associated with poor prognosis. Knockdown RFC2 inhibited proliferation, induced apoptosis, and suppressed migration and invasion of CRC cells. CREB5 was a transcription factor of RFC2, and CREB5 knockdown suppressed RFC2 expression. Furthermore, RFC2 promoted aerobic glycolysis and MET/PI3K/AKT/mTOR pathway. CONCLUSION: RFC2 promoted the progression of CRC cells via activating aerobic glycolysis and the MET/PI3K/AKT/mTOR pathway.


Asunto(s)
Neoplasias Colorrectales , Transducción de Señal , Humanos , Proteínas Proto-Oncogénicas c-akt/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Proteína de Replicación C/metabolismo , Proliferación Celular/genética , Serina-Treonina Quinasas TOR/metabolismo , Neoplasias Colorrectales/patología , Glucólisis , Línea Celular Tumoral
3.
Drug Metab Dispos ; 51(6): 753-763, 2023 06.
Artículo en Inglés | MEDLINE | ID: mdl-36863866

RESUMEN

The human pharmacokinetics, metabolism, and excretion of [14C]-ganaxolone (GNX) were characterized in healthy male subjects (n = 8) following a single 300-mg (150 µCi) oral dose. GNX exhibited a short half-life of 4 hours in plasma, whereas total radioactivity had a half-life of 413 hours indicating extensive metabolism to long-lived metabolites. Identification of the major GNX circulating metabolites required extensive isolation and purification for liquid chromatography-tandem mass spectrometry analysis, together with in vitro studies, NMR spectroscopy, and synthetic chemistry support. This revealed that the major routes of GNX metabolism involved hydroxylation at the 16α-hydroxy position, stereoselective reduction of the 20-ketone to afford the corresponding 20α-hydroxysterol, and sulfation of the 3α-hydroxy group. This latter reaction yielded an unstable tertiary sulfate, which eliminated the elements of H2SO4 to introduce a double bond in the A ring. A combination of these pathways, together with oxidation of the 3ß-methyl substituent to a carboxylic acid and sulfation at the 20α position, led to the major circulating metabolites in plasma, termed M2 and M17. These studies, which led to the complete or partial identification of no less than 59 metabolites of GNX, demonstrated the high complexity of the metabolic fate of this drug in humans and demonstrated that the major circulating products in plasma can result from multiple sequential processes that may not be easily replicated in animals or with animal or human in vitro systems. SIGNIFICANCE STATEMENT: Studies on the metabolism of [14C]-ganaxolone in humans revealed a complex array of products that circulated in plasma, the two major components of which were formed via an unexpected multi-step pathway. Complete structural characterization of these (disproportionate) human metabolites required extensive in vitro studies, along with contemporary mass spectrometry, NMR spectroscopy, and synthetic chemistry efforts, which served to underscore the limitations of traditional animal studies in predicting major circulating metabolites in man.


Asunto(s)
Neuroesteroides , Animales , Humanos , Masculino , Neuroesteroides/análisis , Pregnanolona/análisis , Espectrometría de Masas , Cromatografía Liquida , Cromatografía Líquida de Alta Presión , Heces/química
4.
Int J Colorectal Dis ; 37(8): 1853-1863, 2022 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-35857106

RESUMEN

PURPOSE: Colorectal cancer (CRC) is a common and aggressive gastrointestinal cancer, and the prognostic impact associated with chemotherapy in super elderly (over 80 years old) patients remains poorly defined. We aimed to define the effect of chemotherapy on the prognosis of patients with CRC over 80 years old. PATIENTS AND METHODS: A retrospective study including CRC patients over 80 years old was conducted. The patients were screened from the Surveillance Epidemiology and End Results (SEER) database from 2010 to 2015. Overall survival (OS) and cancer-specific survival (CSS) were applied as the primary and secondary outcome. Cox proportional hazards regression models were used to evaluate factors associated with OS and CSS. Survival curves of OS and CSS were estimated by Kaplan-Meier method and compared by log-rank test. RESULTS: In total, 14,748 CRC patients over 80 years old were included in this study. The median patient age was 85 (IQR: 82-87). All patients were divided into surgical group and non-surgical group. The OS and CSS of the surgical group were significantly better than those of the non-surgical group (P < 0.001). Chemotherapy can improve OS and CSS for patients with stage III and IV (P < 0.001) in surgical group. For the super elderly patients with CRC, chemotherapy significantly improved OS and CSS in all TNM stages in non-surgical group. CONCLUSION: For super elderly patients with colorectal cancer, tumor treatment should not be abandoned because of their age. It is necessary to carry out clinical trials in super elderly patients.


Asunto(s)
Neoplasias Colorrectales , Anciano , Anciano de 80 o más Años , Neoplasias Colorrectales/tratamiento farmacológico , Neoplasias Colorrectales/cirugía , Humanos , Estadificación de Neoplasias , Pronóstico , Estudios Retrospectivos , Programa de VERF , Resultado del Tratamiento
5.
Nutr Res ; 95: 1-18, 2021 11.
Artículo en Inglés | MEDLINE | ID: mdl-34757305

RESUMEN

A key event featured in the early stage of chronic gut inflammatory diseases is the disordered recruitment and excess accumulation of immune cells in the gut lamina propria. This process is followed by the over-secretion of pro-inflammatory factors and the prolonged overactive inflammatory responses. Growing evidence has suggested that gut inflammatory diseases may be mitigated by butyric acid (BA) or butyrate sodium (NaB). Laboratory studies show that BA and NaB can enhance gut innate immune function through G-protein-mediated signaling pathways while mitigating the overactive inflammatory responses by inhibiting histone deacetylase. The regulatory effects may occur in both epithelial enterocytes and the immune cells in the lamina propria. Prior to further clinical trials, comprehensive literature reviews and rigid examination concerning the underlying mechanism are necessary. To this end, we collected and reviewed 197 published reports regarding the mechanisms, bioactivities, and clinical effects of BA and NaB to modulate gut inflammatory diseases. Our review found insufficient evidence to guarantee the safety of clinical practice of BA and NaB, either by anal enema or oral administration of capsule or tablet. The safety of clinical use of BA and NaB should be further evaluated. Alternatively, dietary patterns rich in "fruits, vegetables and beans" may be an effective and safe approach to prevent gut inflammatory disease, which elevates gut microbiota-dependent production of BA. Our review provides a comprehensive reference to future clinical trials of BA and NaB to treat gut inflammatory diseases.


Asunto(s)
Microbioma Gastrointestinal , Ácido Butírico/farmacología , Transducción de Señal , Sodio
6.
FASEB J ; 34(6): 8187-8203, 2020 06.
Artículo en Inglés | MEDLINE | ID: mdl-32388910

RESUMEN

Circular RNAs (circRNAs) function as modulators of microRNAs (miRNAs) and are often involved in cancer progression. This study aims to investigate the underlying mechanism by which circRNA hsa-circ-000684 promotes the progression of gastric cancer (GC). Expression of hsa-circ-000684 and that of ZEB1 mRNA were elevated while microRNA-186 (miR-186) expression was downregulated in GC cell lines and clinical tissues. In addition, the effects of hsa-circ-000684 on the proliferation, migration, invasion, and tube formation of GC cells were examined through gain-and loss-of-function experiments. Furthermore, we introduced tumor xenografts into nude mice to better understand these effects in vivo. Either knockdown of hsa-circ-000684 or upregulation of miR-186 inhibited GC cell proliferation, migration, invasion, and tube formation in vitro, and reduced the xenograft tumor growth in nude mice. Moreover, we found that hsa-circ-000684 and ZEB1 directly bound to miR-186. Hsa-circ-000684 increased the expression of ZEB1 by binding to miR-186. The tumor suppressive effects of hsa-circ-000684 knockdown were reversed by inhibition of miR-186. Collectively, our data show that hsa-circ-000684 reduces the miR-186 expression which leads to an increase in the ZEB1 expression and, consequently, promotion of GC progression.


Asunto(s)
MicroARNs/genética , Oncogenes/genética , ARN Circular/genética , Neoplasias Gástricas/genética , Homeobox 1 de Unión a la E-Box con Dedos de Zinc/genética , Adulto , Anciano , Animales , Carcinogénesis/genética , Línea Celular , Línea Celular Tumoral , Movimiento Celular/genética , Proliferación Celular/genética , Progresión de la Enfermedad , Regulación hacia Abajo/genética , Femenino , Humanos , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Desnudos , Persona de Mediana Edad , ARN Mensajero/genética , Regulación hacia Arriba/genética
7.
Cell Prolif ; 52(4): e12648, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-31199037

RESUMEN

OBJECTIVES: Circular RNAs (circRNAs) exist extensively in the eukaryotic genome. The study aimed to identify the role of hsa_circ_0008365 (Circ-SERPINE2) in gastric carcinoma (GC) cells and its downstream mechanisms. MATERIALS AND METHODS: Gene Expression Omnibus (GEO) database was applied to screen differentially expressed circRNAs. CircInteractome, TargetScan and miRecords websites were used to predict target relationships. qRT-PCR and RNase R treatment were utilised to detect molecule expression and confirm the existence of circ-SERPINE2. RNA pull-down assay and dual-luciferase reporter assay were performed for interaction between circRNA and miRNA or mRNA. EdU assay, colony formation assay, and flow cytometry for apoptosis and cell cycle detections were utilised to assess cell function. Western blot and immunohistochemistry (IHC) assays were applied for detection of proteins in tissues or cells. RESULTS: Circ-SERPINE2 and YWHAZ were upregulated, and miR-375 was downregulated in GC tissues and cells. Circ-SERPINE2 and YWHAZ targetedly bound to miR-375. Circ-SERPINE2 promoted cell proliferation and cell cycle progress and inhibited cell apoptosis by sponging miR-375 and regulating YWHAZ expression in vitro. Circ-SERPINE2 repressed solid tumour growth through enhancing miR-375 expression and reducing YWHAZ expression in vivo. CONCLUSIONS: Circ-SERPINE2 is a novel proliferative promoter through the regulation of miR-375/YWHAZ. Circ-SERPINE2/miR-375/YWHAZ axis might provide a novel therapeutic target of GC.


Asunto(s)
Proteínas 14-3-3/genética , MicroARNs/genética , Serpina E2/genética , Neoplasias Gástricas/genética , Apoptosis/genética , Ciclo Celular/genética , Línea Celular Tumoral , Proliferación Celular/genética , Progresión de la Enfermedad , Regulación hacia Abajo/genética , Regulación Neoplásica de la Expresión Génica/genética , Humanos , ARN , ARN Circular , Neoplasias Gástricas/patología , Regulación hacia Arriba/genética
8.
J Cell Physiol ; 234(10): 18587-18601, 2019 08.
Artículo en Inglés | MEDLINE | ID: mdl-30953349

RESUMEN

Gastric cancer (GC) is a common heterogeneous disease. The critical roles of microRNA-340 (miR-340) in the development and progression of GC were emphasized in accumulating studies. This study aims to examine the regulatory mechanism of miR-340 in GC cellular processes. Initially, microarray technology was used to identify differentially expressed genes and regulatory miRs in GC. After that, the potential role of miR-340 in GC was determined via ectopic expression, depletion, and reporter assay experiments. Expression of secreted phosphoprotein 1 (SPP1), miR-340, phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway, and epithelial-mesenchymal transition (EMT)-related genes was measured. Moreover, to further explore the function of miR-340 in vivo and in vitro, proliferation, apoptosis, migration, invasion, and tumorigenic capacity were evaluated. SPP1 was a target gene of miR-340 which could then mediate the PI3K/AKT signaling pathway by targeting SPP1 in GC. Furthermore, miR-340 levels were reduced and SPP1 was enriched in GC tissues and cells, with the PI3K/AKT signaling pathway being activated. Inhibitory effects of upregulated miR-340 on SPP1 and the PI3K/AKT signaling pathway were confirmed in vivo and in vitro. Overexpression of miR-340 or the silencing of SPP1 inhibited GC cell proliferation, invasion, migration, and EMT process, but promoted apoptosis of GC cells. Typically, targeting of SPP1 by miR-340 may contribute to the inhibition of proliferation, migration, invasion, and EMT of GC cells via suppression of PI3K/AKT signaling pathway.


Asunto(s)
Transición Epitelial-Mesenquimal , MicroARNs/metabolismo , Osteopontina/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Transducción de Señal , Neoplasias Gástricas/genética , Neoplasias Gástricas/patología , Animales , Apoptosis/genética , Secuencia de Bases , Carcinogénesis/genética , Carcinogénesis/patología , Línea Celular Tumoral , Movimiento Celular/genética , Proliferación Celular/genética , Progresión de la Enfermedad , Regulación hacia Abajo/genética , Transición Epitelial-Mesenquimal/genética , Regulación Neoplásica de la Expresión Génica , Silenciador del Gen , Humanos , Ratones Desnudos , MicroARNs/genética , Modelos Biológicos , Invasividad Neoplásica , Osteopontina/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Regulación hacia Arriba/genética
9.
Cancer Biol Ther ; 20(4): 524-536, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-30395767

RESUMEN

We aimed at the effects of long non-coding RNA (lncRNA) SNHG5 on proliferation, metastasis and migration of colorectal cancer (CRC) cells. We also investigated regulatory relationships among miR-132-3p, SNHG5 and CREB5 and their roles in CRC. 25 pairs of samples containing CRC tissues and matched para-tumor tissues were obtained to examine SNHG5, miR-132-3p and CREB5 expression by qRT-PCR or Western blot. The targeted relationship between miR-132-3p and SNHG5 or CREB5 was confirmed by dual luciferase report assay as well as RNA pull down assay. The expression of SNHG5, miR-132-3p and CREB5 in CRC cells were regulated by cell transfection. CRC cellular proliferation was assayed by CCK-8 and meanwhile flow cytometry was adopted to observe apoptosis. Metastasis and migration of CRC cells were determined respectively by means of Transwell assay and scratch test. The effects of SNHG5 on CRC were researched in vivo, too. SNHG5 or CREB5 was up-regulated in CRC tissues and cells, whereas miR-132-3p was down-regulated. Overexpression of SNHG5 and CREB5 resulted in the enhancement of proliferation, metastasis, migration and the inhibition of apoptosis in CRC cells, while miR-132-3p led to the opposite result. LncRNA SNHG5 promoted proliferation, migration and metastasis of CRC cells but inhibited apoptosis by modulating miR-132-3p/CERB5.


Asunto(s)
Movimiento Celular , Proliferación Celular , Neoplasias Colorrectales/patología , Proteína de Unión al Elemento de Respuesta al AMP Cíclico/metabolismo , Regulación Neoplásica de la Expresión Génica , MicroARNs/genética , ARN Largo no Codificante/genética , Animales , Apoptosis , Biomarcadores de Tumor/genética , Biomarcadores de Tumor/metabolismo , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/metabolismo , Proteína de Unión al Elemento de Respuesta al AMP Cíclico/genética , Femenino , Humanos , Ratones , Ratones Desnudos , Metástasis de la Neoplasia , Pronóstico , Tasa de Supervivencia , Células Tumorales Cultivadas , Ensayos Antitumor por Modelo de Xenoinjerto
10.
Cancer Biol Ther ; 19(7): 573-583, 2018 07 03.
Artículo en Inglés | MEDLINE | ID: mdl-29667486

RESUMEN

OBJECTIVE: This study was conducted to investigate the effects of ADP dependent glucokinase antisense RNA 1 (ADPGK-AS1)/ miR-205-5p/ zinc finger E-box binding homeobox 1 (ZEB1) on PC cells. METHODS: Differentially expressed lncRNAs and miRNAs in pancreatic cancer (PC) were identified by microarray analysis. In silico ceRNA analysis was conducted to find out the interactions among lncRNAs, miRNAs and mRNAs. Quantitative real-time PCR (qRT-PCR) was utilized to examine the expression of miR-205-5p and lncRNA ADPGK-AS1 in PC and non-cancerous cells. The association between miR-205-5p and ADPGK-AS1 as well as miR-205-5p and ZEB1 was determined by dual-luciferase reporter gene assay. After manipulating the expression of ADPGK-AS1, mir-205-5p and ZEB1 in PANC-1 and SW-1990 cells, cell proliferation, migration, invasion and apoptosis were respectively confirmed by cell counting kit-8 (CCK-8) assay, transwell assay and TUNEL. Western blot was applied to examine the expression of Epithelial-mesenchymal Transition-related proteins. In vivo experiment was conducted to further determine the effect of miR-205-5p/ZEB1 on tumorigenic ability of PC cells. RESULTS: MiR-205-5p was low-expressed while ZEB1 and ADPGK-AS1 were high-expressed in PC tissues and cells compared with the normal. Dual-luciferase reporter gene assay proved that ADPGK-AS1 could directly target miR-205-5p and miR-205-5p could directly target ZEB1 3'UTR. The expression of MiR-205-5p was negatively correlated with proliferation, migration and invasion, and positively correlated with apoptosis rate of PC cells, while ZEB1 and ADPGK-AS1 had an inversed effect. Further in vitro and in vivo investigation indicated that epithelial-mesenchymal transition (EMT) could be restrained by miR-205-5p through targeting ZEB1. ADPGK-AS1 strongly promoted the tumorigenesis via downregulating miR-205-5p expression and induced the EMT process in vivo. CONCLUSION: ADPGK-AS1 inhibited miR-205-5p and therefore promoted PC progression through activating ZEB1-induced EMT.


Asunto(s)
Transición Epitelial-Mesenquimal/genética , MicroARNs/metabolismo , Neoplasias Pancreáticas/genética , ARN Largo no Codificante/metabolismo , Homeobox 1 de Unión a la E-Box con Dedos de Zinc/genética , Regiones no Traducidas 3'/genética , Animales , Apoptosis/genética , Carcinogénesis/genética , Línea Celular Tumoral , Movimiento Celular/genética , Proliferación Celular/genética , Progresión de la Enfermedad , Perfilación de la Expresión Génica , Regulación Neoplásica de la Expresión Génica , Células HEK293 , Humanos , Ratones , Ratones Endogámicos BALB C , MicroARNs/genética , Neoplasias Pancreáticas/patología , ARN Largo no Codificante/genética , Ensayos Antitumor por Modelo de Xenoinjerto , Homeobox 1 de Unión a la E-Box con Dedos de Zinc/metabolismo
11.
J Med Chem ; 56(6): 2568-80, 2013 Mar 28.
Artículo en Inglés | MEDLINE | ID: mdl-23472952

RESUMEN

Recent efforts to identify treatments for myocardial ischemia reperfusion injury have resulted in the discovery of a novel series of highly potent α,α-disubstituted amino acid-based arginase inhibitors. The lead candidate, (R)-2-amino-6-borono-2-(2-(piperidin-1-yl)ethyl)hexanoic acid, compound 9, inhibits human arginases I and II with IC50s of 223 and 509 nM, respectively, and is active in a recombinant cellular assay overexpressing human arginase I (CHO cells). It is 28% orally bioavailable and significantly reduces the infarct size in a rat model of myocardial ischemia/reperfusion injury. Herein, we report the design, synthesis, and structure-activity relationships (SAR) for this novel series of inhibitors along with pharmacokinetic and in vivo efficacy data for compound 9 and X-ray crystallography data for selected lead compounds cocrystallized with arginases I and II.


Asunto(s)
Aminoácidos/química , Aminoácidos/farmacología , Arginasa/antagonistas & inhibidores , Compuestos de Boro/química , Compuestos de Boro/farmacología , Caproatos/química , Caproatos/farmacología , Descubrimiento de Drogas , Daño por Reperfusión Miocárdica/tratamiento farmacológico , Aminoácidos/farmacocinética , Aminoácidos/uso terapéutico , Animales , Arginasa/química , Compuestos de Boro/farmacocinética , Compuestos de Boro/uso terapéutico , Células CHO , Caproatos/farmacocinética , Caproatos/uso terapéutico , Cricetinae , Cricetulus , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacocinética , Inhibidores Enzimáticos/farmacología , Inhibidores Enzimáticos/uso terapéutico , Humanos , Masculino , Modelos Moleculares , Conformación Proteica , Ratas , Relación Estructura-Actividad
12.
J Nat Prod ; 76(2): 157-69, 2013 Feb 22.
Artículo en Inglés | MEDLINE | ID: mdl-23356946

RESUMEN

The monoglucuronides and sulfates of epicatechin, 3'-O-methylepicatechin, and 4'-O-methylepicatechin, respectively, were synthesized as authentic bioanalytical standards. Reversed-phase HPLC methods capable of baseline separation of the glucuronides and sulfates have been developed. Both the epicatechin glucuronides and sulfates were stable in the solid state when stored under ambient conditions and in aqueous solution when stored refrigerated. These results should prove invaluable to the research community as analytical standards as well as in future studies of the biological and pharmacological effects of epicatechin in humans.


Asunto(s)
Catequina/análogos & derivados , Glucurónidos/síntesis química , Ésteres del Ácido Sulfúrico/síntesis química , Catequina/síntesis química , Catequina/química , Cromatografía Líquida de Alta Presión , Glucurónidos/química , Humanos , Estructura Molecular , Resonancia Magnética Nuclear Biomolecular , Ésteres del Ácido Sulfúrico/química
13.
Bioorg Med Chem Lett ; 17(15): 4378-81, 2007 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-17574417

RESUMEN

Novel anthranilamides were surprisingly found to exert additional activity on B-RAF. Corresponding thiophene, pyrazole, and thiazole core analogs were prepared as VEGFR-2 inhibitors with c-KIT, and B-RAF activity. Compounds in the phenyl, thiophene, and thiazole series are in vivo active.


Asunto(s)
Antineoplásicos/farmacología , Neoplasias/tratamiento farmacológico , Inhibidores de Proteínas Quinasas/farmacología , Receptor 2 de Factores de Crecimiento Endotelial Vascular/antagonistas & inhibidores , Animales , Antineoplásicos/uso terapéutico , Línea Celular Tumoral , Humanos , Ratones , Inhibidores de Proteínas Quinasas/uso terapéutico , Relación Estructura-Actividad
15.
J Org Chem ; 69(21): 7371-4, 2004 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-15471497

RESUMEN

Polyhaloanilines bearing an ortho halogen atom undergo smooth nucleophilic aromatic substitution reactions with anionic sulfur nucleophiles at relatively mild temperatures (95-120 degrees C). These reactions are very efficient and highly ortho-selective. With potassium/sodium O-ethyl xanthate as a nucleophile, subsequent cyclization follows to afford halogenated 2(3H)-benzothiazolethiones (2-mercaptobenzothiazoles) in high yields.

16.
Org Lett ; 5(9): 1587-9, 2003 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-12713330

RESUMEN

A highly efficient diastereoselective, carboxylate-directed homogeneous hydrogenation of cyclic olefins with use of Wilkinson's catalyst is described. Under the optimized reaction conditions, better than 99% de was achieved. The experimental protocol is very simple and readily amenable to scale-up. [reaction: see text]

17.
J Org Chem ; 68(9): 3729-32, 2003 May 02.
Artículo en Inglés | MEDLINE | ID: mdl-12713390

RESUMEN

We have developed a modification of the Miyaura arylboronate synthesis(1a) by substituting a ligandless palladium catalyst for PdCl(2)(dppf). Palladium acetate, free of ligand, was found highly effective for such coupling reactions. This modified procedure is advantageous over the original Miyaura synthesis in ease of workup, catalyst removal, and low catalyst cost. Furthermore, the boronates formed in this manner can be used directly for Suzuki coupling reactions in a one-pot fashion. The biaryl products have improved impurity profiles and reduced heavy metal contamination.

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