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1.
Water Res ; 194: 116953, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33657494

RESUMO

The quasi-Monte Carlo (QMC) method was enhanced to solve the population balance model (PBM) including aggregation and fragmentation processes for simulating the temporal evolutions of characteristic sizes and floc size distributions (FSDs) of cohesive sediments. Ideal cases with analytical solutions were firstly adopted to validate this QMC model to illustrate selected pure aggregation, pure fragmentation, and combined aggregation and fragmentation systems. Two available laboratory data sets, one with suspended kaolinite and the other with a mixture of kaolinite and montmorillonite, were further used to monitor the FSDs of cohesive sediments in controlled shear conditions. The model results show reasonable agreements with both analytical solutions and laboratory experiments. Moreover, different QMC schemes were tested and compared with the standard Monte Carlo scheme and a Latin Hypercube Sampling scheme to optimize the model performance. It shows that all QMC schemes perform better in both accuracy and time consumption than standard Monte Carlo scheme. In particular, compared with other schemes, the QMC scheme using Halton sequence requires the least particle numbers in the simulated system to reach reasonable accuracy. In the sensitivity tests, we also show that the fractal dimension and the fragmentation distribution function have large impacts on the predicted FSDs. This study indicates a great advance in employing QMC schemes to solve PBM for simulating the flocculation of cohesive sediments.


Assuntos
Fractais , Sedimentos Geológicos , Floculação , Caulim , Método de Monte Carlo
2.
Am J Trop Med Hyg ; 2021 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-33591933

RESUMO

Knowledge of the clinical progress of severe fever with thrombocytopenia syndrome (SFTS) and the associated predictors of mortality is important for providing appropriate treatment in severe cases. A multihospital retrospective study was conducted in three SFTS-endemic cities, in 2018. Of the 208 SFTS-confirmed cases, there were 189 survivors and 19 deaths. The median age was 64 years; 104 (50.0%) patients were men, and 188 (90.4%) were farmers. Furthermore, 203 (97.6%) patients reported fever and 70 (33.7%) reported fatigue. Most fatal cases had complications including multiple-organ failure, central nervous syndrome (CNS) abnormalities, and disseminated intravascular coagulation. During the fever phase, alanine transaminase, aspartate aminotransferase (AST), blood urea nitrogen (BUN), creatinine, D-dimer, glucose, hydroxybutyrate dehydrogenase, lactate dehydrogenase (LDH), procalcitonin, prothrombin time, and uric acid levels were higher in fatal than in nonfatal cases (P < 0.05). Creatine kinase (CK), CK-MB (CKMB), AST, and LDH levels were significantly lower in nonfatal than in fatal cases (P < 0.05). Central nervous syndrome abnormalities (odds ratio [OR] = 20.9, 95% CI: 4.3, 100), body temperature ≥ 38.5°C (OR = 23.2, 95% CI: 3.4, 158), BUN levels ≥ 6.4 mmol/L (OR = 9.9, 95% CI: 2.2, 44), CKMB levels ≥ 100 U/L (OR = 33.2, 95% CI: 5.8, 192), and LDH levels ≥ 1,000 U/L (OR = 8.3, 95% CI: 1.9, 37) were predictors of mortality. Our findings reveal that the presence of specific complications and laboratory parameters may serve as predictors of mortality and aid in early identification of severe SFTS cases in clinical practice.

3.
Emerg Microbes Infect ; 9(1): 2509-2514, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33238813

RESUMO

We investigated a multi-family cluster of 22 cases in Jixi, where pre-symptomatic and asymptomatic transmission resulted in at least 41% of household infections of SARS-CoV-2. Our study illustrates the challenge of controlling COVID-19 due to the presence of asymptomatic and pre-symptomatic transmission even when extensive testing and contact tracing are conducted.

4.
Curr Neurovasc Res ; 2020 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-32748746

RESUMO

OBJECTIVES: This study aims to explore in detail the mechanism of the carbon monoxide releasing molecule-3 (CORM-3) in regulating the activity of microglia (MG) in the treatment of radiation brain injury (RBI). METHODS: The brain injury models of BV2 cells and Balb/C mice were established and randomly divided into three groups: the normal control group (CON), the single radiation group (RAD), and the radiation plus CORM-3 intervention group (RAD+CORM). Immunofluorescence was used to observe the effects on activation of the MG. The expressions of inflam-matory factors, such as intercellular adhesion molecule-1 (ICAM-1) and inducible nitric oxide synthase (iNOS), were detected by Western blot. Neuron apoptosis and regeneration in the radiation brain injury (RBI)model were detected by neuronal nuclear antigen (NeuN)+TUNEL and NeuN+BrdU double staining. A Morris water maze was used to assess the spa-tial learning and memory of the mice. RESULTS: Within 48 hours after radiation, CORM-3 inhibited activation of the MG, blocked the phosphorylation of P38, and increased the expression of ICAM-1 and iNOS. Therefore, CORM-3 might alleviate MG-mediated neuronal apoptosis and promote neuralregeneration in the subgranular zone (SGZ) of the dentate gyrus of the hippocampus. CORM-3 could in-crease the swimming distance and platform-stay time of the mice in the target platform quadrant after radiation. CONCLUSION: CORM-3 could effectively improve the inflammatory response induced by activation of the MG, reduce neu-ronal apoptosis, promote neural regeneration, and improve the learning and memory performance of mice after radiation.

5.
Nat Commun ; 5: 3661, 2014 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-24739462

RESUMO

Lack of cellular differentiation is a key feature of nasopharyngeal carcinoma (NPC), but it also presents as a unique opportunity for intervention by differentiation therapy. Here using RNA-seq profiling analysis and functional assays, we demonstrate that reduced IKKα expression is responsible for the undifferentiated phenotype of NPC. Conversely, overexpression of IKKα induces differentiation and reduces tumorigenicity of NPC cells without activating NF-κB signalling. Importantly, we describe a mechanism whereby EZH2 directs IKKα transcriptional repression via H3K27 histone methylation on the IKKα promoter. The differentiation agent, retinoic acid, increases IKKα expression by suppressing EZH2-mediated H3K27 histone methylation, resulting in enhanced differentiation of NPC cells. In agreement, an inverse correlation between IKKα (low) and EZH2 (high) expression is associated with a lack of differentiation in NPC patient samples. Collectively, these findings demonstrate a role for IKKα in NPC differentiation and reveal an epigenetic mechanism for IKKα regulation, unveiling a new avenue for differentiation therapy.


Assuntos
Quinase I-kappa B/metabolismo , Neoplasias Nasofaríngeas/metabolismo , Complexo Repressor Polycomb 2/metabolismo , Western Blotting , Carcinoma , Ciclo Celular/genética , Ciclo Celular/fisiologia , Diferenciação Celular/genética , Diferenciação Celular/fisiologia , Linhagem Celular Tumoral , Imunoprecipitação da Cromatina , Proteína Potenciadora do Homólogo 2 de Zeste , Epigênese Genética/genética , Imunofluorescência , Regulação Neoplásica da Expressão Gênica , Humanos , Carcinoma Nasofaríngeo , Neoplasias Nasofaríngeas/genética , Complexo Repressor Polycomb 2/genética , RNA Interferente Pequeno , Reação em Cadeia da Polimerase Via Transcriptase Reversa
6.
PLoS One ; 9(3): e90048, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24595299

RESUMO

BACKGROUND: Intracavitary brachytherapy (ICBT) is usually applied as boost radiotherapy for superficial residual of nasopharyngeal carcinoma (NPC) after primary extern-beam radiptherapy (ERT). Here, we evaluated the outcome of endoscope-guided interstitial intensity-modulated brachytherapy (IMBT) boost radiation for deep-seated residual NPC. METHODOLOGY/PRINCIPAL FINDINGS: Two hundred and thirteen patients with residual NPC who were salvaged with brachytherapy boost radiation during 2005-2009 were analyzed retrospectively. Among these patients, 171 patients had superficial residual NPC (≤1 cm below the nasopharyngeal epithelium) were treated with ICBT boost radiation, and interstitial IMBT boost radiation was delivered to 42 patients with deep-seated residual NPC (>1 cm below the nasopharyngeal epithelium). We found that IMBT boost subgroup had a higher ratio of T2b (81.0% VS 34.5%, P<0.001) and stage II (90.5% VS 61.4%, P = 0.001) than that of ICBT boost subgroup. The dosage of external-beam radiotherapy in the nasopharyngeal (63.0±3.8 VS 62.6±4.3 Gray (Gy), P = 0.67) and regional lymph nodes (55.8±5.0 VS 57.5±5.7 Gy, P = 0.11) was comparable in both groups. For brachytherapy, IMBT subgroup had a lower boost radiation dosage than ICBT subgroup (11.0±2.9 VS 14.8±3.2 Gy, P<0.01). Though the IMBT group had deeper residual tumors and received lower boost radiation dosages, both subgroups had the similar 5-year actuarial overall survival rate (IMBT VS ICBT group: 96.8% VS 93.6%, P = 0.87), progression-free survival rate (92.4% VS 86.5%, P = 0.41) and distant metastasis-free survival rate (94.9% VS 92.7%, P = 0.64). Moreover, IMBT boost radiation subgroup had a similar local (97.4% VS 94.4%, P = 0.57) and regional (95.0% VS 97.2%, P = 0.34) control to ICBT subgroup. The acute and late toxicities rates were comparable between the both subgroups. CONCLUSIONS/SIGNIFICANCE: IMBT boost radiation may be a promising therapeutic selection for deep-seated residual NPC.


Assuntos
Braquiterapia/métodos , Endoscópios , Neoplasias Nasofaríngeas/radioterapia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Taxa de Sobrevida , Resultado do Tratamento
7.
Breast J ; 19(4): 382-7, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23721399

RESUMO

Solid neuroendocrine breast carcinoma (solid NEBC) is a relatively uncommon malignant tumor of the breast. The purpose of our study was to explore the incidence and clinical features of this tumor, and to evaluate the efficacy of adjuvant chemotherapy and endocrine therapy for patients with solid NEBC. Of 7542 breast cancers registered during the period from March 2004 to April 2011, 22 patients (0.29%) who underwent surgery had tumors that were histologically confirmed as solid NEBC, and were enrolled in this study. The age range of these patients was 29-77 years (mean 52.5 years). Patients were staged according to the 7th edition of the pathologic tumor-node-metastasis (pTNM) staging system. Biopsies or resection specimens were reviewed and reclassified according to the World Health Organization (WHO) 2003 classification. We recorded clinical features including gender and age, chief complaint, and past medical history, tumor characteristics including size, location, preoperative diagnosis, and pathologic and immunohistochemical findings, the therapeutic schedule, and the follow-up results. Solid NEBC is a rare and distinct category of malignant disease of the breast, with good prognosis, and in most early-stage cases, is resectable. The role of adjuvant chemotherapy and endocrine therapy in solid NEBC may be limited and should be studied further.


Assuntos
Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/patologia , Carcinoma Neuroendócrino/tratamento farmacológico , Carcinoma Neuroendócrino/patologia , Adulto , Idoso , Antineoplásicos Hormonais/uso terapêutico , Neoplasias da Mama/epidemiologia , Neoplasias da Mama/metabolismo , Neoplasias da Mama/cirurgia , Carcinoma Neuroendócrino/epidemiologia , Carcinoma Neuroendócrino/metabolismo , Carcinoma Neuroendócrino/cirurgia , Quimioterapia Adjuvante , China , Terapia Combinada , Feminino , Seguimentos , Humanos , Pessoa de Meia-Idade , Período Pós-Operatório , Resultado do Tratamento
8.
Cancer Biother Radiopharm ; 28(10): 697-702, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23806020

RESUMO

OBJECTIVE: This research was to investigate the role of goserelin in combination with endocrine therapy for the treatment of advanced breast cancer in premenopausal women positive for hormone receptors. METHODS: We retrospectively analyzed 40 patients as the treatment group with advanced breast cancer who, were positive for hormone receptors, received goserelin in combination with endocrine therapy and 40 patients as the control group received endocrine therapy alone, matched for age, gender, receptor status, and tumor stage. RESULTS: The median period of follow-up was 38.9 months. The response status at 6 months, the overall clinical benefit rate was 87.5% and 70.0% in the treatment group and control group, respectively. The mean progression-free survival (PFS) in the treatment group and control group was 27.9 and 16.9 months, respectively. The 1-, 2-, and 3-year PFS rates were 87.5%, 66.2%, and 49.7%, respectively, in the treatment group and 59.2%, 38.8%, and 35.3%, respectively, in the control group (p=0.076). The 1-, 2-, and 3-year overall survival (OS) rates were 100%, 87.2%, and 76.6%, respectively, in the treatment group and 90.0%, 74.2%, and 55.8%, respectively, in the control group (p=0.048). For the treatment group with age <40 years, PFS (p=0.036) and OS (p=0.014) were significantly longer than the control group, but it was no effect on the prognosis with the patients aged ≥40 years. Continued use of goserelin after disease progress again in the median survival time was significantly longer than nonusers (28.2 months vs. 7.0 months), and there is the potential benefit of OS (p=0.070). CONCLUSIONS: For premenopausal hormone receptor-positive advanced breast cancer, goserelin-combined endocrine therapy can be used for those <40 years, the standard endocrine treatment for patients, we recommend continued use of goserelin for patients with disease progress again.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/metabolismo , Adulto , Fatores Etários , Antineoplásicos Hormonais/administração & dosagem , Neoplasias da Mama/patologia , Estudos de Casos e Controles , Intervalo Livre de Doença , Feminino , Gosserrelina/administração & dosagem , Gosserrelina/efeitos adversos , Humanos , Pessoa de Meia-Idade , Pré-Menopausa , Prognóstico , Receptores Estrogênicos/metabolismo , Receptores de Progesterona/metabolismo , Estudos Retrospectivos , Resultado do Tratamento , Adulto Jovem
9.
J Investig Med ; 61(1): 34-9, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23160184

RESUMO

INTRODUCTION: Our purpose was to assess the efficacy of radiation therapy in the treatment of locoregional recurrence of esophageal squamous cell carcinoma recurrence after curative resection. METHODS: Patients with local esophageal squamous cell carcinoma recurrence who were treated at the Cancer Prevention and Treatment Center of Sun Yat-sen University from January 1990 to December 2002 and whose initial treatment was complete surgical resection (N = 152) were included. Of the 152 patients, 60 patients received treatment with radiation therapy, and the others did not receive radiation. None of the included patients received chemotherapy or radiotherapy before surgery. The Kaplan-Meier method was used to calculate the cumulative survival rate. RESULTS: The median survival time was 16.0 ± 2.7 months for those who received radiotherapy versus 6.5 ± 1.6 months for those who did not (P < 0.001). The median survival time was greater (22.3 ± 4.0 months) for patients who receive a dosage greater than 50 Gy compared with those patients who received a dosage of 50 Gy or less (7.7 ± 0.3 months; P = 0.033). The overall 3- and 5-year survival rates were 16.4% and 10.4%, respectively. The 1-, 2-, and 3- year recurrence-free survival rates were 56.1 ± 4.3%, 32.9 ± 4.1%, and 22.0 ± 3.7%, respectively. CONCLUSION: Radiotherapy may help improve the survival rate in patients with local esophageal squamous cell carcinoma recurrence after complete surgical resection who have no history of radiotherapy.


Assuntos
Carcinoma de Células Escamosas/mortalidade , Carcinoma de Células Escamosas/radioterapia , Neoplasias Esofágicas/mortalidade , Neoplasias Esofágicas/radioterapia , Recidiva Local de Neoplasia/mortalidade , Recidiva Local de Neoplasia/radioterapia , Idoso , Carcinoma de Células Escamosas do Esôfago , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Taxa de Sobrevida/tendências , Resultado do Tratamento
10.
Autophagy ; 8(12): 1798-810, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23026799

RESUMO

We have previously shown that elevated expression of mitotic kinase aurora kinase A (AURKA) in cancer cells promotes the development of metastatic phenotypes and is associated clinically with adverse prognosis. Here, we first revealed a clinically positive correlation between AURKA and autophagy-associated protein SQSTM1 in breast cancer and further demonstrated that AURKA regulated SQSTM1 through autophagy. Indeed, depletion by siRNA or chemical inhibition of AURKA by the small molecule VX-680 increased both the level of microtubule-associated protein 1 light chain 3-II (LC3-II) and the number of autophagosomes, along with decreased SQSTM1. Conversely, overexpression of AURKA inhibited autophagy, as assessed by decreased LC3-II and increased SQSTM1 either upon nutrient deprivation or normal conditions. In addition, phosphorylated forms of both RPS6KB1 and mechanistic target of rapamycin (MTOR) were elevated by overexpression of AURKA whereas they were suppressed by depletion or inhibition of AURKA. Moreover, inhibition of MTOR by PP242, an inhibitor of MTOR complex1/2, abrogated the changes in both LC3-II and SQSTM1 in AURKA-overexpressing BT-549 cells, suggesting that AURKA-suppressed autophagy might be associated with MTOR activation. Lastly, repression of autophagy by depletion of either LC3 or ATG5, sensitized breast cancer cells to VX-680-induced apoptosis. Similar findings were observed in cells treated with the autophagy inhibitors chloroquine (CQ) and bafilomycin A 1 (BAF). Our data thus revealed a novel role of AURKA as a negative regulator of autophagy, showing that AURKA inhibition induced autophagy, which may represent a novel mechanism of drug resistance in apoptosis-aimed therapy for breast cancer.


Assuntos
Autofagia , Mama/enzimologia , Mama/patologia , Resistencia a Medicamentos Antineoplásicos , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Apoptose/efeitos dos fármacos , Aurora Quinase A , Aurora Quinases , Autofagia/efeitos dos fármacos , Regulação para Baixo/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Ativação Enzimática/efeitos dos fármacos , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Pessoa de Meia-Idade , Piperazinas/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Proteínas Serina-Treonina Quinases/metabolismo , RNA Interferente Pequeno/metabolismo , Proteína Sequestossoma-1 , Serina-Treonina Quinases TOR/metabolismo
11.
Head Neck ; 34(10): 1383-8, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22143978

RESUMO

BACKGROUND: Endoscopic nasopharyngectomy is a new salvage treatment for locally recurrent nasopharyngeal carcinoma (NPC). However, how to resurface the nasopharyngeal defects in endoscopic endonasal approaches to avoid persistent postoperative headache, to the best of our knowledge, has not been reported. METHODS: From September 2009 to August 2010, we used a modified posterior pedicle nasal septum and floor mucoperiosteum flap (nasal septum and floor flap, NSFF) after endoscopic nasopharyngectomy in 12 patients with locally recurrent NPC. Most of the nasal septum and floor mucoperiosteum, except for the posterior pedicle, was harvested to cover the nasopharyngeal defects. RESULTS: All NSFFs successfully covered the entire nasopharyngeal defects and relined the nasopharynx with good functional recovery. The nasopharyngeal wounds recovered in 28 days (range, 14 to 56 days), and the donor-site wounds recovered in 46.5 days (range, 24-84 days). No reconstruction-related complications or disease recurrences were observed. CONCLUSION: The NSFF is a safe and promising reconstructive option to resurface the nasopharyngeal defect after endoscopic nasopharyngectomy in patients with locally recurrent NPC.


Assuntos
Endoscopia/métodos , Septo Nasal/transplante , Recidiva Local de Neoplasia/cirurgia , Periósteo/transplante , Retalhos Cirúrgicos/irrigação sanguínea , Adulto , Carcinoma , Estudos de Coortes , Feminino , Seguimentos , Sobrevivência de Enxerto , Humanos , Imagem por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Septo Nasal/cirurgia , Carcinoma Nasofaríngeo , Neoplasias Nasofaríngeas/patologia , Neoplasias Nasofaríngeas/cirurgia , Nasofaringe/cirurgia , Recidiva Local de Neoplasia/patologia , Duração da Cirurgia , Periósteo/cirurgia , Qualidade de Vida , Procedimentos Cirúrgicos Reconstrutivos/métodos , Estudos Retrospectivos , Fatores de Tempo , Resultado do Tratamento
12.
Org Lett ; 8(3): 355-8, 2006 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-16435833

RESUMO

[structure: see text]. The optically active molecular electronic wires (S)- and (R)-7 containing an oligo-arylene-ethynylene structure and a chiral 1,1'-binaphthyl unit are synthesized. These molecules are incorporated into nanowell devices by self-assembly on the gold surface. In the nanowell devices, the median currents from the molecules containing both S and R enantiomers are significantly smaller than those from the pure S or R molecule. Compounds (R)- and (S)-7 are also less conductive than the fully conjugated oligo-phenylene-ethynylene-thiol molecules.

13.
Carbohydr Res ; 337(3): 207-15, 2002 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-11844490

RESUMO

A highly concise and effective synthesis of the mannose octasaccharide of the N-linked glycan in the adhesion domain of human CD2 was achieved via TMSOTf-promoted selective 6-glycosylation of a trisaccharide 4,6-diol acceptor with a pentasaccharide donor, followed by deprotection. The pentasaccharide was constructed by selective 3,6-diglycosylation of 1,2-O-ethylidene-beta-D-mannopyranose with 2-O-acetyl-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl trichloroacetimidate, while the trisaccharide was obtained by selective 3-O-glycosylation of allyl 4,6-O-benzylidene-alpha-D-mannopyranoside with the same disaccharide trichloroacetimidate, followed by debenzylidenation. The mannose hexasaccharide antigenic factor 13b was synthesized by condensation of a trisaccharide donor, 2-O-acetyl-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->3)-4,6-di-O-acetyl-2-O-benzoyl-alpha-D-mannopyranosyl trichloroacetimidate, with a trisaccharide acceptor, methyl 3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranoside, followed by deprotection.


Assuntos
Antígenos CD2/química , Manosídeos/síntese química , Oligossacarídeos/síntese química , Glicoproteínas/química , Glicosilação , Humanos , Manosídeos/química , Conformação Molecular , Oligossacarídeos/química
14.
Carbohydr Res ; 337(5): 383-90, 2002 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-11861011

RESUMO

The tetrasaccharide repeating unit of Escherichia coli O9a, alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->3)-D-Manp, and the pentasaccharide repeating unit of E. coli O9 and Klebsiella O3, alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->3)-D-Manp, were synthesized as their methyl glycosides. Thus, selective 3-O-allylation of p-methoxyphenyl alpha-D-mannopyranoside via a dibutyltin intermediate gave p-methoxyphenyl 3-O-allyl-alpha-D-mannopyranoside (2) in good yield. Benzoylation (-->3), then removal of 1-O-methoxyphenyl (right arrow4), and subsequent trichloroacetimidation afforded the 3-O-allyl-2,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl trichloroacetimidate (5). Condensation of 5 with methyl 4,6-O-benzylidene-alpha-D-mannopyranoside (6) selectively afforded the (1-->3)-linked disaccharide 7. Benzoylation of 7, debenzylidenation, benzoylation, and deallylation gave methyl 2,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->3)-2,4,6-tri-O-benzoyl-alpha-D-mannopyranoside (11) as the disaccharide acceptor. Coupling of 11 with (1-->2)-linked mannose disaccharide donor 17 or trisaccharide donor 21, followed by deacylation, furnished the target tetrasaccharide and pentasaccharide, respectively.


Assuntos
Escherichia coli/química , Klebsiella/química , Manose/química , Antígenos O/química , Oligossacarídeos/síntese química , Sequência de Carboidratos , Oligossacarídeos/química , Relação Estrutura-Atividade
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