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Doctoral Thesis
DOI
https://doi.org/10.11606/T.60.2008.tde-28082008-104925
Document
Author
Full name
Adriane da Silveira Gomes
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Ribeirão Preto, 2008
Supervisor
Committee
Silva, Carlos Henrique Tomich de Paula da (President)
Bastos, Jairo Kenupp
Chin, Chung Man
Oliveira, Dioneia Camilo Rodrigues de
Yagui, Carlota de Oliveira Rangel
Title in Portuguese
Síntese e modelagem molecular de carboidratos com potencial atividade anti-glucosidase
Keywords in Portuguese
carba-açúcares
Inibidores de glucosidase
modelagem molecular
pseudodissacarídeos
Abstract in Portuguese
Os carboidratos presentes nos glicoconjugados apresentam alto grau de complexidade e diversidade estrutural, desempenhando um importante papel em diversos processos biológicos. As glucosidases, enzimas responsáveis pela clivagem de ligações O-glicosídicas em oligossacarídeos e glicoconjugados, participam de processos bioquímicos fundamentais do metabolismo e também estão envolvidas na biossíntese de glicoproteínas e glicoesfingolipídeos. Diversos inibidores de glucosidases de origem natural ou sintética têm sido descritos, como por exemplo: acarbose (1), miglitol (2), voglibose (3) e N-butil-desoxi-nojirimicina (4); sendo 1, 2 e 3 indicados para tratamento de diabetes mellitus tipo II e 4 para o controle da doença de Gaucher. Considerando a importância do planejamento e da síntese de novos inibidores de glucosidases, bem como a necessidade de obtenção de modelos tridimensionais para glucosidases, os objetivos deste trabalho foram: i) sintetizar carba-açúcares e pseudodissacarídeos potencialmente anti-glucosidase, ii) avaliar suas atividades inibitórias empregando a enzima ?-D-glucosidase de Saccharomyces cerevisiae e iii) aplicar técnicas de bioinformática e modelagem molecular na construção de um modelo estrutural 3D por homologia da sacarase intestinal de rato e realizar estudos de relação estrutura-atividade baseado no padrão farmacofórico calculado para os inibidores descritos. Neste sentido, a partir do precursor-chave (3/2,4)-2,3,4-tri-O-benzil-5-hidroxi-cicloexanona (12), obtido em 6 etapas, foram sintetizados diferentes carba-açúcares. Adicionalmente, reações de aminação redutiva, rearranjo alílico e "click chemistry" foram empregadas na síntese dos pseudodissacarídeos inéditos 3-(2,4-dibenziloxi-fenilamino)-2,4,6-tri-O-benzil-3-desoxi-?-D-glucopiranosídeo de metila (81), 1-(2',3',4'-tri-O-benzil-5'-oxo-cicloexanil)-4,6-di-O-acetil-2,3-didesoxi-hex-2-enopiranosídeo (89) e 2-{4-[(1H-1,2,3-triazol-4-il)metoxi]-2,4-di-O-benzil-fenila}-1,3,4,6-tetra-O-acetil-2-desoxi-?-D-glucopiranosídeo (99), respectivamente. O composto (3/2,4)-2,3,4,5-tetraidroxi-cicloexanona (46) foi submetido a estudos de inibição enzimática e apresentou moderada atividade de inibição da enzima ?-D-glucosidase. As simulações de docking com o modelo construído da sacarase de rato bem como a determinação do padrão farmacofórico forneceram novas informações estruturais sobre o sítio ativo desta enzima e do modo de ligação de diferentes inibidores. Portanto, as estratégias sintéticas, os estudos de cinética enzimática e de modelagem molecular realizados durante o trabalho resultaram em contribuições relevantes no que diz respeito à química de carboidratos, permitindo avaliar potenciais inibidores da enzima ?-glucosidase in silico, os quais poderão ser sintetizados e submetidos a novos ensaios enzimáticos.
Title in English
Synthesis and Molecular Modeling of Carbohydrate with Potential Anti-glucosidase Activity
Keywords in English
carba-sugars
Glucosidase inhibitors
molecular modeling
pseudodissaccharides
Abstract in English
Carbohydrates of glycoconjugates display high degree of complexity and structural diversity, playing a central role in biological processes. Glucosidases are enzymes that catalyze the cleavage of glycosidic bonds in oligosaccharides or glycoconjugates, being essentials in several metabolic pathways and in the biosynthesis of glycoproteins and glycosfingolipids. Several glucosidase inhibitors from natural and synthetic sources have been described, such as: acarbose (1), miglitol (2), voglibose (3) and N-butyl-desoxy-nojirimycin (4). Compounds 1, 2 and 3 are used in the treatment of type II diabetes mellitus and 4 for patients with Gaucher's disease. Concerning to the importance of the design and synthesis of new glucosidase inhibitors, as well as the need of 3D models for glucosidases, the aims of this work were: i) the synthesis of potentially anti-glucosidase carba-sugars and pseudodisaccharides, ii) the evaluation of its inhibitory activities by using ?-D-glucosidase from Saccharomyces cerevisiae and iii) the use of bioinformatics and molecular modeling techniques for creation of a 3D structural homology model of rat intestinal sucrase to accomplish the structure-activity relationships studies concerning to the pharmacophoric pattern of the reported inhibitors. Thus, starting with the key precursor 12, prepared in six steps, different carba-sugars were synthesized. Additionally, reductive amination reactions, allylic rearrangement and "click chemistry" were applied on the synthesis of novel pseudosaccharides 81, 89 and 99, respectively. Compound 46 was assayed for enzymatic inhibition and demonstrated reasonable activity for the inhibition of ?-D-glucosidase. Docking simulations by using the rat sucrase model and the determination of pharmacophoric pattern provided significant information concerning to the enzyme's active site and the inhibitor's binding pattern. Therefore, the synthetic strategies, enzymatic kinetic assays and molecular modeling studies performed in this work resulted in relevant contributions to the carbohydrate chemistry, making possible for our research group to evaluate potential ?-glucosidase inhibitors in silico, which can be synthesized and assayed for enzymatic activity in the future.
 
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Publishing Date
2008-09-11
 
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