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1.
Carbohydr Res ; 485: 107807, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31520817

RESUMO

A series of tricyclic benzimidazole-iminosugars 1(a-f) and 2(a-f) were synthesized and evaluated for their their inhibitory activities against five glycosidases. The synthesis initiated from the benzyl protected sugar (aldehyde) 5 that reacted with 1,2-diaminobenzene to afford aldo-benzimidazole 6 by the iodine-induced oxidative condensation. Then, tricyclic compound 7 was obtained in high yields of 73%-87% by the key Mitsunobu reaction through intramolecular cyclization of the unprotected OH and the NH in 6. After removal of the benzyl group in CF3SO3H, the target tricyclic benzimidazole-iminosugars 1 and 2 were achieved. The protocol was effective for the preparation of the tricyclic iminosugar in satisfactory yield. The results of the glycosidase inhibitory activities of 1 and 2 showed that three compounds derived from d-ribose exhibited specific and good inhibitory effects on ß-glucosidase. Among them, 1e-1 was the best one with IC50 value of 5.37 µM. All hydroxyl groups on ß-position would be favourable to the inhibitory activity of such tricyclic benzimidazole-iminosugars against ß-glucosidase.

2.
Carbohydr Res ; 478: 10-17, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-31039450

RESUMO

A series of novel tricyclic quinazolinone-iminosugars 1 (a-c) were synthesized from the benzyl protected sugars through three steps. Firstly, the benzyl protected sugar (aldehyde) 5 reacted with o-aminobenzamide by the iodine-induced oxidative condensation to afford the corresponding aldo-quizanolinone 6. Secondly, through the intramolecular cyclization of the unprotected OH and the amide NH in 6, the tricyclic compounds 7 and 8 were constructed by the key Mitsunobu reaction. Finally, removal of the benzyl group gave the target tricyclic quinazolinone-iminosugars 1. The protocol was effective for the preparation of the tricyclic iminosugars in satisfactory yield. Interestingly, an unusual C-2 epimerization was observed with d-mannose and d-ribose compounds under the conditions of the Mitsunobu reaction that generated the products having the trans configuration at the C-2 and C-3 positions. Unfortunately, such tricyclic quinazolinone-iminosugars showed no inhibitory effects on the tested five glycosidases.


Assuntos
Inibidores Enzimáticos/farmacologia , Glicosídeo Hidrolases/antagonistas & inibidores , Imino Açúcares/farmacologia , Quinazolinonas/farmacologia , Aspergillus niger/enzimologia , Canavalia/enzimologia , Configuração de Carboidratos , Café/enzimologia , Ciclização , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Escherichia coli/enzimologia , Glicosídeo Hidrolases/metabolismo , Imino Açúcares/síntese química , Imino Açúcares/química , Prunus dulcis/enzimologia , Quinazolinonas/síntese química , Quinazolinonas/química
3.
Carbohydr Res ; 456: 45-52, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-29274552

RESUMO

Azasugar aldehydes 6a and 6b containing azido groups were prepared from D-mannose. Three novel tetracyclic azasugars fused benzo[e][1,3]thiazin-4-one 9a-1, 9a-2 and 9a-3 were conveniently synthesized from 6a by the tandem intramolecular Staudinger/aza-Wittig/cyclization reaction under microwave radiation. Two unexpected elimination compounds 8b-1 and 8b-2 were achieved as the main products from 6b in the same processes. The newly synthesized azasugars were examined for their HIV reverse transcriptase (RT) inhibitory activities. The results showed that all the tested compounds could effectively inhibit RT activity. Among them, compound 8b-1 with the protective group (isopropylidene group) was the best one with the IC50 value of 0.76 µM. The structure activity relationship analysis suggested that improvement of the molecular hydrophilicity might be beneficial for their anti-HIV RT activities.


Assuntos
Inibidores da Transcriptase Reversa/química , Inibidores da Transcriptase Reversa/farmacologia , HIV-1/efeitos dos fármacos , Micro-Ondas , Estrutura Molecular , Relação Estrutura-Atividade
4.
Nanotechnology ; 26(45): 455204, 2015 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-26491032

RESUMO

A neuro-inspired computing paradigm beyond the von Neumann architecture is emerging and it generally takes advantage of massive parallelism and is aimed at complex tasks that involve intelligence and learning. The cross-point array architecture with synaptic devices has been proposed for on-chip implementation of the weighted sum and weight update in the learning algorithms. In this work, forming-free, silicon-process-compatible Ta/TaOx/TiO2/Ti synaptic devices are fabricated, in which >200 levels of conductance states could be continuously tuned by identical programming pulses. In order to demonstrate the advantages of parallelism of the cross-point array architecture, a novel fully parallel write scheme is designed and experimentally demonstrated in a small-scale crossbar array to accelerate the weight update in the training process, at a speed that is independent of the array size. Compared to the conventional row-by-row write scheme, it achieves >30× speed-up and >30× improvement in energy efficiency as projected in a large-scale array. If realistic synaptic device characteristics such as device variations are taken into an array-level simulation, the proposed array architecture is able to achieve ∼95% recognition accuracy of MNIST handwritten digits, which is close to the accuracy achieved by software using the ideal sparse coding algorithm.


Assuntos
Metodologias Computacionais , Impedância Elétrica , Reconhecimento Automatizado de Padrão , Semicondutores , Sinapses/fisiologia , Aprendizagem , Modelos Teóricos , Aprendizado de Máquina não Supervisionado
5.
Front Neurosci ; 9: 488, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26732664

RESUMO

The purpose of this work was to demonstrate the feasibility of building recurrent artificial neural networks with hybrid complementary metal oxide semiconductor (CMOS)/memristor circuits. To do so, we modeled a Hopfield network implementing an analog-to-digital converter (ADC) with up to 8 bits of precision. Major shortcomings affecting the ADC's precision, such as the non-ideal behavior of CMOS circuitry and the specific limitations of memristors, were investigated and an effective solution was proposed, capitalizing on the in-field programmability of memristors. The theoretical work was validated experimentally by demonstrating the successful operation of a 4-bit ADC circuit implemented with discrete Pt/TiO2- x /Pt memristors and CMOS integrated circuit components.

6.
Nanotechnology ; 23(7): 075201, 2012 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-22260949

RESUMO

Using memristive properties common for titanium dioxide thin film devices, we designed a simple write algorithm to tune device conductance at a specific bias point to 1% relative accuracy (which is roughly equivalent to seven-bit precision) within its dynamic range even in the presence of large variations in switching behavior. The high precision state is nonvolatile and the results are likely to be sustained for nanoscale memristive devices because of the inherent filamentary nature of the resistive switching. The proposed functionality of memristive devices is especially attractive for analog computing with low precision data. As one representative example we demonstrate hybrid circuitry consisting of an integrated circuit summing amplifier and two memristive devices to perform the analog multiply-and-add (dot-product) computation, which is a typical bottleneck operation in information processing.

7.
Nanoscale Res Lett ; 4(10): 1178-1182, 2009 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-20596279

RESUMO

The structural and optical characterizations of titania incorporated with alumina nanocrystals have been presented in this paper and the films exhibit excellent properties like low current density, small hysteresis as well as high photoluminescence quantum yields of about 361 nm. These properties are promising for the applications in future electronic devices.

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