Bibliografías temáticas / INDOLENT PRECURSOR

Índice

Artículos de revistas
Tesis
Capítulos de libros
Actas de conferencias

Literatura académica sobre el tema "INDOLENT PRECURSOR"

Autor: Grafiati

Publicado: 11 de marzo de 2023

Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros

Elija tipo de fuente:

Consulte las listas temáticas de artículos, libros, tesis, actas de conferencias y otras fuentes académicas sobre el tema "INDOLENT PRECURSOR".

Junto a cada fuente en la lista de referencias hay un botón "Agregar a la bibliografía". Pulsa este botón, y generaremos automáticamente la referencia bibliográfica para la obra elegida en el estilo de cita que necesites: APA, MLA, Harvard, Vancouver, Chicago, etc.

También puede descargar el texto completo de la publicación académica en formato pdf y leer en línea su resumen siempre que esté disponible en los metadatos.

Artículos de revistas sobre el tema "INDOLENT PRECURSOR"

Pinto-Lopes, Pedro, Francisco Adao Fonseca, Roberto Silva, Pedro von Hafe y Elsa Fonseca. "Indolent systemic mastocytosis limited to the bone: a case report and review of the literature". Sao Paulo Medical Journal 131, n.º 3 (2013): 198–204. http://dx.doi.org/10.1590/1516-3180.2013.1313460.

Texto completo

Resumen

CONTEXT Systemic mastocytosis is defined as a clonal disorder of mast cells and their precursor cells and is currently classified as a myeloproliferative neoplasm. Its clinical course has a wide spectrum, ranging from indolent disease, with normal life expectancy, to highly aggressive disease, associated with multisystemic involvement and poor overall survival. The aim of this study was to report a case of indolent systemic mastocytosis, focusing on the diagnostic challenges, with a review of the literature. CASE REPORT A 79-year-old Caucasian woman with osteoporosis was evaluated at the Emergency Department because of complaints of low back pain. Before this, she had consulted an orthopedist and had undergone some imaging examinations, namely a bone scan that revealed a “superscan” pattern. Due to her pain complaints and these test results, the patient was admitted to the Department of Internal Medicine. After undergoing several analytical tests and some additional imaging examinations to rule out some important differential diagnoses, she then underwent bone marrow biopsy, which made it possible to identify indolent systemic mastocytosis. CONCLUSION Systemic mastocytosis is a rare entity that is difficult to diagnose. Its symptoms are often unspecific and frequently ignored. Skeletal changes may be the first and only manifestation of the disease and in some cases, like this one, the diagnosis is made only after histological examination. The key point for the diagnosis is to contemplate the possibility of systemic mastocytosis.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Canberk, Sule. "Precursor and borderline lesions of the thyroid (indolent lesions of epithelial origin): from theory to practice". Gland Surgery 9, n.º 5 (octubre de 2020): 1724–34. http://dx.doi.org/10.21037/gs-20-429.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

Lussier, Tyler, Natalie Schoebe y Sabine Mai. "Risk Stratification and Treatment in Smoldering Multiple Myeloma". Cells 11, n.º 1 (31 de diciembre de 2021): 130. http://dx.doi.org/10.3390/cells11010130.

Texto completo

Resumen

Smoldering multiple myeloma is a heterogeneous asymptomatic precursor to multiple myeloma. Since its identification in 1980, risk stratification models have been developed using two main stratification methods: clinical measurement-based and genetics-based. Clinical measurement models can be subdivided in three types: baseline measurements (performed at diagnosis), evolving measurements (performed over time during follow-up appointments), and imaging (for example, magnetic resonance imaging). Genetic approaches include gene expression profiling, DNA/RNA sequencing, and cytogenetics. It is important to accurately distinguish patients with indolent disease from those with aggressive disease, as clinical trials have shown that patients designated as “high-risk of progression” have improved outcomes when treated early. The risk stratification models, and clinical trials are discussed in this review.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Marchegiani, Giovanni, Stefano Andrianello, Tommaso Pollini, Andrea Caravati, Giuseppe Malleo, Marco Biancotto, Claudio Bassi y Roberto Salvia. "Natural History of Intraductal Papillary Mucinous Neoplasm of the Pancreas Reappraisal of the Indolent Precursor of Pancreatic Cancer". Journal of the American College of Surgeons 227, n.º 4 (octubre de 2018): e37-e38. http://dx.doi.org/10.1016/j.jamcollsurg.2018.08.099.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

Purdy, Adam, Firas Ido y Deborah Stahlnecker. "Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia (DIPNECH): A Case of Indolent Pulmonary Nodules Diagnosed with Robotic-Assisted Navigational Bronchoscopy". Case Reports in Pulmonology 2021 (10 de diciembre de 2021): 1–4. http://dx.doi.org/10.1155/2021/6312296.

Texto completo

Resumen

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is an atypical pulmonary disorder with limited understanding. Given the rare nature of this disease, it is essential to obtain adequate tissue pathology to confirm the diagnosis. This disease is mainly diagnosed in middle-aged, nonsmoking females, and it is now accepted as a precursor lesion to pulmonary carcinoid tumors. DIPNECH presents with characteristic radiographic and histologic findings, but its diagnosis, management, and prognosis are often underrecognized and poorly understood. Those with symptoms may present with shortness of breath, wheezing, and persistent cough and are often misdiagnosed with reactive airway disease. Pulmonary function testing may reveal airflow obstruction and air trapping. Imaging is characterized by multiple lung nodules, typically less than 5 mm in size, with a background mosaic attenuation on computed tomography imaging. Histologically, DIPNECH can be suspected based on the presence of hyperplastic neuroendocrine cells. DIPNECH is considered a precursor to invasive neuroendocrine tumor, and up to 50% of patients may have a well-differentiated neuroendocrine tumor at the time of presentation. Here, we present the case of a 46-year-old female with a history of ulcerative colitis on mesalamine who presented with a 6-month history of ongoing shortness of breath, chest tightness, wheezing, and cough. She was initially diagnosed with asthma before imaging later revealed as multiple pulmonary nodules with a diffuse mosaic pattern. Using robotic-assisted navigational bronchoscopy, she underwent sampling of a dominant 1.8 cm right middle lobe pulmonary nodule and pathology was consistent with low-grade neuroendocrine tumor.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Garcia-Montero, Andres C., Maria Jara-Acevedo, Ivan Alvarez-Twose, Cristina Teodosio, Laura Sanchez-Muñoz, Javier Ignacio Muñoz-Gonzalez, Andrea Mayado et al. "KIT D816V Mutation Positive Bone Marrow Mesenchymal Stem Cells in Indolent Systemic Mastocytosis Are Associated with Disease Progression". Blood 126, n.º 23 (3 de diciembre de 2015): 4058. http://dx.doi.org/10.1182/blood.v126.23.4058.4058.

Texto completo

Resumen

Abstract PURPOSE: Multilineageinvolvement of bone marrow (BM) hematopoiesis by the somatic KIT D816V mutation is present in a subset of adult indolent systemic mastocytosis (ISM) patients in association with a poorer prognosis. Here we investigated the potential involvement of BM mesenchymal stem cells (MSC) from ISM patients by the KIT D816V mutation and its potential impact on disease progression and outcome. METHODS: The KIT D816V mutation was investigated in highly-purified BM MSC and other BM cell populations from 83 ISM patients followed for a median of 116 months. MC clonality was further evaluated in female patients by the pattern of inactivation of the X chromosome (XCIP). RESULTS: KIT D816V-mutated MSC were detected in 22/83 (27%) ISM patients. All MSC-mutated patients had multilineage KIT mutation (100% vs. 30%, p=0.0001) and they more frequently showed involvement of lymphoid plus myeloid BM cells (59% vs 22%; P =.03) and a polyclonal XCIP of the KIT- mutated BM MC (64% vs 0%; P =0.01) vs other multilineage ISM cases. Moreover, presence of KIT D816V-mutated MSC was associated with more advanced disease features of ISM, a greater rate of disease progression (50% vs 17%; P =.04) and a shorter progression-free survival at 10, 20 and 30 years (P ≤.003). CONCLUSION: Overall, these results support the notion that ISM patients with mutated MSC may have acquired the KIT mutation in a common pluripotent progenitor cell, prior to differentiation into MSC and hematopoietic precursor cells, before the X-chromosome inactivation process occurs. From a clinical point of view, acquisition of the KIT mutation in an earlier BM precursor cell confers a significantly greater risk for disease progression and a poorer outcome. Disclosures No relevant conflicts of interest to declare.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Marchegiani, Giovanni, Stefano Andrianello, Tommaso Pollini, Andrea Caravati, Marco Biancotto, Giuseppe Malleo, Claudio Bassi y Roberto Salvia. "The natural history of intraductal papillary mucinous neoplasms of the pancreas: Reappraisal of the indolent precursor of pancreatic cancer". Pancreatology 18, n.º 4 (junio de 2018): S2—S3. http://dx.doi.org/10.1016/j.pan.2018.05.011.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

Marchegiani, G., S. Andrianello, T. Pollini, A. Caravati, M. Biancotto, G. Malleo, C. Bassi y R. Salvia. "The natural history of intraductal papillary mucinous neoplasm of the pancreas: Reappraisal of the indolent precursor of pancreatic cancer". HPB 20 (septiembre de 2018): S195. http://dx.doi.org/10.1016/j.hpb.2018.06.051.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

López, Cristina, Pablo Mozas, Armando López-Guillermo y Sílvia Beà. "Molecular Pathogenesis of Follicular Lymphoma: From Genetics to Clinical Practice". Hemato 3, n.º 4 (26 de septiembre de 2022): 595–614. http://dx.doi.org/10.3390/hemato3040041.

Texto completo

Resumen

Follicular lymphoma (FL), a generally indolent disease that derives from germinal center (GC) B cells, represents around 20–25% of all new lymphomas diagnosed in Western countries. The characteristic t(14;18)(q32;q21) translocation that places the BCL2 oncogene under control of the immunoglobulin heavy-chain enhancer occurs in pro- or pre-B cells. However, additional secondary alterations are required for the development of overt FL, which mainly affects genes involved in epigenetic and transcriptional regulation, signaling and B cell differentiation, the BCR/NF-κB pathway, and proliferation/apoptosis. On the other hand, new insights into the FL pathogenesis suggest that FL lacking the BCL2 translocation might be a distinct biological entity with genomic features different from the classical FL. Although FL is considered an indolent disease, around 10–20% of cases eventually transform to an aggressive lymphoma, usually a diffuse large B cell lymphoma, generally by a divergent evolution process from a common altered precursor cell acquiring genomic alterations involved in the cell cycle and DNA damage responses. Importantly, FL tumor cells require interaction with the microenvironment, which sustains cell survival and proliferation. Although the use of rituximab has improved the outlook of most FL patients, further genomic studies are needed to identify those of high risk who can benefit from innovative therapies. This review provides an updated synopsis of FL, including the molecular and cellular pathogenesis, key events of transformation, and targeted treatments.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Khanlari, Mahsa y Jennifer R. Chapman. "Follicular lymphoma: updates for pathologists". Journal of Pathology and Translational Medicine 56, n.º 1 (15 de enero de 2022): 1–15. http://dx.doi.org/10.4132/jptm.2021.09.29.

Texto completo

Resumen

Follicular lymphoma (FL) is the most common indolent B-cell lymphoma and originates from germinal center B-cells (centrocytes and centroblasts) of the lymphoid follicle. Tumorigenesis is believed to initiate early in precursor B-cells in the bone marrow (BM) that acquire the t(14;18)(q32;q21). These cells later migrate to lymph nodes to continue their maturation through the germinal center reaction, at which time they acquire additional genetic and epigeneticabnormalities that promote lymphomagenesis. FLs are heterogeneous in terms of their clinicopathologic features. Most FLs are indolent and clinically characterized by peripheral lymphadenopathy with involvement of the spleen, BM, and peripheral blood in a substantial subset of patients, sometimes accompanied by constitutional symptoms and laboratory abnormalities. Diagnosis is established by the histopathologic identification of a B-cell proliferation usually distributed in an at least partially follicular pattern, typically, but not always, in a lymph node biopsy. The B-cell proliferation is biologically of germinal center cell origin, thus shows an expression of germinal center-associated antigens as detected by immunophenotyping. Although many cases of FLs are typical and histopathologic features are straightforward, the biologic and histopathologic variability of FL is wide, and an accurate diagnosis of FL over this disease spectrum requires knowledge of morphologic variants that can mimic other lymphomas, and rarely non-hematologic malignancies, clinically unique variants, and pitfalls in the interpretation of ancillary studies. The overall survival for most patients is prolonged, but relapses are frequent. The treatment landscape in FL now includes the application of immunotherapy and targeted therapy in addition to chemotherapy.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Más fuentes

Tesis sobre el tema "INDOLENT PRECURSOR"

Mcausland, Donald Euan Reynolds. "Arynes in synthesis : new reaction and precursor development". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/arynes-in-synthesisnew-reaction-and-precursor-development(1f59c4ec-dc6d-487b-9bc4-c5a99d5bc030).html.

Texto completo

Resumen

The arylation of readily accessible N-tosyl hydrazones has been achieved using arynes generated in situ under mild conditions. The resulting N-tosyl-N-aryl hydrazones undergo a one-pot Fischer indole reaction on the addition of acid, giving a synthesis of protected indoles that avoids handling unstable intermediates and arylhydrazines. A new route to functionalised 2-(trimethylsilyl)phenyl triflate aryne precursors via Suzuki cross-coupling has been developed. The method allows the incorporation of a wide range of aryl and heteroaryl groups and reactions of arynes generated from these novel precursors have been demonstrated, including a cyclotrimerisation and a fluorenone synthesis. Work was also undertaken on aryne σ-insertion reactions. The addition of benzyne to ynamides was found to result in its net insertion between the nitrogen and acetylene species. The reaction proceeds from attack at the terminal carbon in an analogous manner to C(sp)–O insertions.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Ciccolini, Cecilia. "Synthesis of Mono and Poly-Heterocycles starting from 1,2-Diaza-1,3-Dienes (or precursors) as Building Blocks". Doctoral thesis, Urbino, 2020. http://hdl.handle.net/11576/2674162.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

Wen, Xin. "The Utilization of Sulfonylhydrazones as New Radical Precursors for Asymmetric Radical C–H Alkylation via Co(II)-Based Metalloradical Catalysis". Thesis, Boston College, 2019. http://hdl.handle.net/2345/bc-ir:108292.

Texto completo

Resumen

Thesis advisor: X. Peter Zhang
Asymmetric C–H functionalization represents one of the central topics in modern organic chemistry, which allows for the direct installation of functional groups onto ubiquitous C–H bonds in organic molecules. Among numerous elegant strategies, transition metal-catalyzed C–H alkylation with diazo compounds represents one of the most powerful methods for C–C bond formation. Different from Fischer metallocarbene-based C–H insertion reactions, cobalt(II)-based metalloradical catalysis (MRC) is recently proven to be capable of activating acceptor/acceptor diazo compounds for radical C–H alkylation reactions via H-atom abstraction. In this dissertation, we have developed several systems by utilizing less-explored aryl and alkyl diazomethanes as new radical precursors for highly enantioselective radical C–H alkylation reactions, which permit the efficient synthesis of different optically active heterocyclic compounds. First, we have demonstrated the feasibility of using aryl aldehyde-derived sulfonylhydrazones as new radical precursors for enantioselective radical C–H alkylation to synthesis enantioenriched 2,3-dihydrobenzofuran derivatives. Notably, a general and mild way for in situ generation of diazo compounds have been identified by using 2,4,6-triisopropyl sulfonyl hydrazone as diazo precursor, which allow us to regulate the reaction temperature to achieve the high enantioselectivity for the desired radical reactions. Second, the utility of Co(II)-based MRC has been further highlighted by enantioselective indoline synthesis. Through the design and synthesis of new catalysts, the system is shown to have a broad spectrum of substrate scope, forming various 2-substituted indolines with up to 98% yield and 96% ee. A series of mechanistic studies further support the underlying stepwise radical alkylation pathway. Finally, we further expand the applicability of MRC to even more challenging diazo compounds, aliphatic diazomethanes. Starting from alkyl aldehyde-derived sulfonylhydrazones as diazo precursors, the Co(II)-based radical alkylation reactions allow for the enantioselective synthesis for common 2-substituted tetrahydrofuran structures with high yields and excellent enantioselectivities
Thesis (PhD) — Boston College, 2019
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

Los estilos APA, Harvard, Vancouver, ISO, etc.

Marchegiani, Giovanni. "THE NATURAL HISTORY OF INTRADUCTAL PAPILLARY MUCINOUS NEOPLASM OF THE PANCREAS: REAPPRAISAL OF THE INDOLENT PRECURSOR OF PANCREATIC CANCER". Doctoral thesis, 2018. http://hdl.handle.net/11562/978425.

Texto completo

Resumen

INTRODUCTION Evidences from surgical series have been condensed into several guidelines for the management of Intraductal Papillary Mucinous Neoplasms of the pancreas (IPMNs). However, still a gap must be filled to better understand their biological behavior. Aim of the present study is to describe the natural history of IPMNs observed at a high-volume center for thirty years. METHODS All patients with a radiological or pathological diagnosis of IPMN referred to The Pancreas Institute, University of Verona Hospital Trust, from 1985 to 2016 were included. Growth rates were analyzed through a linear-mixed model. The development of worrisome features (WF), high-risk stigmata (HRS), and pancreatic cancer (PC), survival and risk for surgery were also analyzed. RESULTS Of 2189 observed patients, 1529 were included in the analysis. The overall median follow-up was 43 months. Three hundred and thirteen patients were sent to surgery upfront, while 181 after initial surveillance. The overall growth rate was 1mm/year. For about half of cases any dimensional change was documented. The presence of high risk stigmata (HRS), age <75 years, and cyst size >30mm at diagnosis were associated to a faster growth rate. During follow-up, trivial IPMNs developed WF in 6.5% of cases and HRS in 0.6%. Overall, 3.5% of patients developed PC after a median time of 28 months. Of these patients, 72% previously developed HRS/WF. Of 1043 initially observed trivial branch duct (BD) IPMNs, 16 eventually developed PC with 10% occurring after 15 years of follow-up. HRS and growth rate were independent predictors of PC. Growth rate was the only difference between IPMNs developing PC and those remaining stable after more than 5 years of follow-up (n=399). The mean estimated disease specific survival (DSS) for the overall population exceeded 19 years. Only 1.9% of BD-IPMNs developed PC, with a resulting 5-years DSS rate of 99.3%. Standardized incidence ratio of PC for patients with trivial BD-IPMN was 21 (95% CI 10 – 38), whereas was only 1.8 (95% CI 0.5 – 4.7) considering patients > 65 years. CONCLUSIONS IPMN of the pancreas is the indolent precursor of PDAC that will not show a detectable growth during follow-up in half of the cases. Those rapidly growing (>2.50 mm/year) will likely progress to pancreatic cancer through the development of WF and HRS during the first year of follow-up. In patients > 65 y/o, the presence of a BD-IPMN without WF or HRS at diagnosis might not increase the risk of developing PC than in the general population

Los estilos APA, Harvard, Vancouver, ISO, etc.

Chen, Yu-Jen y 陳俞臻. "The Synthesis and Photochemistry of Radical Pair Precursors: N-Benzenesulfonyl Substituted Pyrroles, Imidazole and Indole". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/3287f4.

Texto completo

Resumen

碩士
國立交通大學
應用化學系
90
A series of 39, 47, 52 and 53 in 2-methyltetrahydrofuran glass matrices at 77 K were irradiated with 230-325 nm (NiSO4-filtered, UV light), which gave triplet EPR spectra, and the zero-field splitting (zfs) parameters D' values are 0.0228, 0.0225, 0.0190 and 0.0176 cm-1, respectively. At 4 K, the D' values of 51 and 47 are 0.0239 and 0.0237 cm-1, respectively. The radical pairs derived from 51 (12-44 K) and 47 (8-52 K) both showed linear Curie plots, thereby indicating either the ground state are triplets or that singlet and triplet states are degenerate (≦30 cal/mole difference). An addition product of Ts and MNP was observed when 51 was photolyzed in the presence of spin trapping agent. N-benzenesulfonyl substituted hetercyclic molecules 85 and 88 also gave triplet EPR spectra, which are consistent with triplet radical pairs. Results indicate that nitro-sulfur bonds were easily cleaved by 230-325 nm photolysis, and the results are supported by ab initio calculations. Therefore, the reported D' value (0.0226 cm-1) of a biradical by Professor Berson in the photolysis of N-tosyl pyrrole diazene 18 (J. A. Berson, J. Am. Chem. Soc. 1997, 119, 1416.) may not be a triplet biradical and could be a triplet radical pair instead.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Capítulos de libros sobre el tema "INDOLENT PRECURSOR"

Politi, V., M. V. Lavaggi, G. Di Stazio y A. Margonelli. "Indole-3-Pyruvic Acid as a Direct Precursor of Kynurenic Acid". En Advances in Experimental Medicine and Biology, 515–18. Boston, MA: Springer New York, 1991. http://dx.doi.org/10.1007/978-1-4684-5952-4_57.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

Grogan, Martha. "Cardiac amyloidosis". En ESC CardioMed, 1545–49. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198784906.003.0373.

Texto completo

Resumen

Cardiac amyloidosis is an important cause of heart failure and cardiac arrhythmias, yet cardiologists often miss the diagnosis. Immunoglobulin light-chain amyloidosis (AL) is relatively rare, but likely underdiagnosed. The median survival of untreated patients with cardiac AL is 6 months after the onset of heart failure, highlighting the importance of early diagnosis. Wild-type transthyretin amyloidosis (ATTR) is increasingly recognized, especially in males over the age of 60 years. Although the clinical course of wild-type ATTR is more indolent, the median survival is approximately 3.5 years from diagnosis. Typical echocardiographic findings of increased left and right ventricular wall thickness, diastolic dysfunction, and pericardial effusion may suggest cardiac amyloidosis, along with abnormal delayed gadolinium enhancement and difficulty nulling the myocardium on cardiac magnetic resonance imaging. For AL, a tissue diagnosis is required. In contrast, ATTR may be diagnosed non-invasively with grade 2/3 uptake by nuclear scintigraphy in the absence of a monoclonal protein. Treatment of cardiac amyloidosis is entirely dependent on the type of amyloid and is directed at the underlying precursor protein or disrupting existing deposits. Cardiac care is supportive and challenging. Standard heart failure medications such as beta blockers and angiotensin-converting enzyme inhibitors are not routinely indicated and often cause haemodynamic deterioration. Outcomes of source-directed therapy for AL are improving and several clinical trials of treatment for ATTR are ongoing.

Los estilos APA, Harvard, Vancouver, ISO, etc.

"Alkaloids I". En Natural Product Biosynthesis, 264–315. The Royal Society of Chemistry, 2022. http://dx.doi.org/10.1039/bk9781839165641-00264.

Texto completo

Resumen

Historically, alkaloids were defined by their alternating solubilities in acidic aqueous solutions, as amine cations, and in organic solvents, as neutral amines, allowing early purification of otherwise unrelated scaffolds, driven by the protonation/deprotonation equilibria. Some 27 000 alkaloid natural products have been purified and characterized, with structures ranging from coniine to caffeine, piperine, quinine, morphine, scopolamine, tubocurarine, and strychnine. Amino acids are the building blocks for common classes of alkaloids, such as those listed above, by early decarboxylation to amines for further complexity generation. The identity of the amino acid precursor is one basis for mechanistic classification of alkaloid subfamilies. Another is the type of nitrogen-containing ring systems in alkaloid products, including pyrrolidines, tropanes, and pyrrolizidines from ornithine; quinolizidines and indolizidine from lysine; isoquinolines from phenylalanine and tyrosine; quinazoline and quinolines from anthranilate; and indole alkaloids from tryptophan. Representative biosynthetic routes to these alkaloid heterocycles, lysergic acid, ergotamines, indolocarbazoles, and strictosidine, as well as recent elucidation of the route to colchicine, are delineated.

Los estilos APA, Harvard, Vancouver, ISO, etc.

"Isoprenoids/Terpenes". En Natural Product Biosynthesis, 192–263. The Royal Society of Chemistry, 2022. http://dx.doi.org/10.1039/bk9781839165641-00192.

Texto completo

Resumen

This largest class of natural products, with >75 000 known structures, arises from a pair of five-carbon isopentenyl diphosphate isomers, one acting as a π-electron double bond carbon nucleophile, the other as an allylic cation electrophile in C–C bond alkylations. Isoprene/terpene chain growth thus occurs five carbons at a time in head-to-tail couplings by prenyl transferase enzymes. At both the C15 or C20 chain length stages, enzymes can carry out related head-to-head chain couplings to generate the C30 hexaene squalene or the C40 nonaene phytoene. Squalene is the precursor to cyclase-mediated conversion to tetracyclic sterol frameworks and pentacyclic plant systems, such as amyrin and cycloartenol. The C10 (geranyl-PP = monoterpene), C15 (farnesyl-PP = sesquiterpene), and C20 (geranylgeranyl = diterpene) head-to-tail coupled metabolites can undergo many variations of internal carbocation-mediated cyclizations to generate a large array of mono- to tetracyclic olefins and alcohols. The predominant animal sterol is the C27 membrane lipid cholesterol, available from the initial C30 biosynthetic tetracyclic lanosterol by oxygenative removal of three C–CH3 groups. This phase of sterol metabolism marks a shift from carbocation-based reactions, to radical chemistry by oxygenases, as nine O2 molecules are consumed. In further conversion of cholesterol to the female sex hormone estradiol, another eight O2 molecules are consumed, for a total of 17 O2 being reductively split in the metabolic traverse from lanosterol to cholesterol. Meroterpenoid assembly involves the intersection of isoprene biosynthetic machinery with polyketide- or indole-processing enzymes.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Taber, Douglass. "Alkaloid Synthesis: (-)-Aurantioclavine (Stoltz), (-)-Esermethole (Nakao/Hiyama/ Ogoshi), (-)-Kainic Acid (Tomooka), Dasycarpidone (Bennasar), (-)-Cephalotaxine (Ishibashi) and Lysergic Acid (Fujii/Ohno)". En Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0060.

Texto completo

Resumen

Intriguing strategies have been developed for the stereocontrolled assembly of complex alkaloid structures. Brian M. Stoltz of Caltech prepared (J. Am. Chem. Soc. 2008, 130, 13745) the enantiomerically-pure alcohol precursor to the secondary amine 1 by enantioselective oxidation of the racemic alcohol. Intramolecular Mitsunobu coupling of 1 then led to (-)-Aurantioclavine 3. Yoshiaki Nakao and Tamejiro Hiyama of Kyoto University and Sensuke Ogoshi of Osaka University developed (J. Am. Chem. Soc. 2008, 130, 12874) an enantioselective Ni catalyst for the cyclization of 4 to 5. Oxidation and cyclization then delivered (-)-Esermethole 6. Although the sulfonamide 7 appears to be prochiral, in fact its two most stable conformations are bent, and enantiomers of each other, with a significant barrier for interconversion. Katsuhiko Tomooka of Kyushu University separated (Tetrahedron Lett. 2008, 49, 6327) the enantiomers of 7, then carried the enantiomercially-pure 7 on, by Pd-catalyzed Cope rearrangement, to 8 and so to (-)-Kainic Acid 9. M.-Lluïsa Bennasar of the University of Barcelona prepared (J. Org. Chem. 2008, 73, 9033) the acyl selenide 11 from the indole 10. While the radical derived from 11 might have been expected to undergo 5-exo cyclization, in the event the 6-endo mode dominated, to give Dasycarpidone 12 and its diastereomer. Hiroyuki Ishibashi of Kanazawa University showed (Organic Lett. 2008, 10, 4129) that the radical cascade cyclization of the enamine 13, derived from diethyl tartrate, proceeded with remarkable diastereocontrol, to give 14. The amide 14 was converted to (-)-Cephalotaxine 15. Nobutaka Fujii and Hiroaki Ohno, also of Kyoto University, used (Organic Lett. 2008, 10, 5239) a Pd catalyst to mediate the cascade cyclization of 16 to 17. Although 16 has two stereogenic centers, including the allene, it is the aminated stereogenic center of 17 that sets the absolute configuration of the product Lysergic Acid 18. One intermediate in the conversion of 16 to the tetracyclic 17 is the tricyclic π-allyl Pd complex. If all the material could be channeled through that pathway, there is a good chance that the chiral Trost catalyst could effectively control the absolute configuration of the aminated stereogenic center as it is formed, leading to the enantiomerically enriched product 18.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Actas de conferencias sobre el tema "INDOLENT PRECURSOR"

Трофимов, Б., B. Trofimov, Н. Гусарова y N. Gusarova. "The development of original methodologies of directed synthesis of le-Carbs their analogs and precursors base donacetylene and its derivatives". En Topical issues of translational medicine: a collection of articles dedicated to the 5th anniversary of the day The creation of a department for biomedical research and technology of the Irkutsk Scientific Center Siberian Branch of RAS. Москва: INFRA-M Academic Publishing LLC., 2017. http://dx.doi.org/10.12737/conferencearticle_58be81ec92d17.

Texto completo

Resumen

New reactions, which have been discovered and continue to be developed in A.E. Favorsky Irkutsk institute of chemistry SB RAS on the basis of acetylene, a product of oil, gas and coal processing and multi-faceted building block for organic synthesis, have been considered. These reactions provide for the shortest routes to construction of fundamental heterocyclic scaffolds (pyrroles, imidazoles, pyrazoles, indoles, pyridines, dihydropyridines, etc.) with desirable and optimum combination of functional pharmacophoric groups and fragments, which are responsible for antiviral (HIV, flu), antitumor, tuberculostatic and hypotensive activities.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Blasko, Gy, G. Blasko, G. Sas y Cs Szantay. "MODULATION OF THROMBIN-MEDIATED REACTIONS IN HAEMOSTASIS- BY TREQUINSIN AND ITS ANALOGUES." En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643432.

Texto completo

Resumen

A new pyrimido/6,1-a/-isoquinoline derivative ,/Ref.1 / developed by Hoechst and named Trequinsine has been reported to be a powerful inhibitor of cAMP phosphodiesterase and platelet aggregation having a potency nearly similar to prostacyclin. We synthesized Trequins-in (1), its indole derivative (4) , as well as their precursors (2 3) and subjected them to a study in order to evaluate their effects on haemostasis. Surprisingly they exhibited a modulatory effect only on reactions mediated mainly by thrombin. They inhibited platelet aggregation (ICc:q for Trequinsin: 13 + 2.5 ng/ml, for indole derivatives: 1-3 /ig/ml); 1, 2, 4 enhanced the amidolytic activity of CC-thrombin towards S-2238 substrate within a narrow range of submicromolar concentrations but they did not exert any effect on the activity or the inactivation of Factor Xa and plasmin.Compound 2 proved to be an inhibitor of prostacyclin production of rat aortic tissue (Trequinsin has much less effect) but in contrary to this 3. and 4 exerted an enhancing effect on the total prostacyclin production.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Ofrecemos descuentos en todos los planes premium para autores cuyas obras están incluidas en selecciones literarias temáticas. ¡Contáctenos para obtener un código promocional único!